Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpclett.4c01206

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcb.3c07919

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/jacs.3c08922

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Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

A π-type hydrogen bonding between the OH group and the π electron is a crucial factor for the conformational preference of the molecular structure with a flexible group. However, the information on the effect of the substituent on the OH/π interaction is insufficient. The laser-induced fluorescence (LIF) excitation, the dispersed fluorescence (DF), the IR–UV hole-burning, and the IR dip spectra of jet-cooled 2-(4-methoxyphenyl)ethanol were measured for the first time. Almost all bands observed in the spectral region of 35 550–36 500 cm−1 in the LIF excitation spectrum were successfully assigned with the DF and the IR–UV hole-burning spectra coupled with the quantum chemical calculation at M06-2x/6-311G and MP2/6-311G levels. Five conformers were found in the LIF excitation spectrum. The most stable conformer was Ggπ, and the second most stable conformer was Ggπ′ (the trans rotamer of the methoxy group for Ggπ). Ggπ and Ggπ′ had the OH group directed toward the π electron system of the benzene ring. The OH stretching frequency of Ggπ/Ggπ′ of MPE in the IR dip spectra was red-shifted against that of Ggπ of phenylethanol, indicating that the introduction of the methoxy group would enhance the intramolecular OH/π interaction. In addition, the torsional vibration between the benzene ring and the side chain (−CH2CH2OH) (mode 63) was observed in the DF spectra of the Ggπ–00 and Ggπ′–00 band excitation, but their intensities were rather different, resulting from the different orientation of the OH group for each conformer toward the π electron system. The methoxy group would increase the negative charge on the benzene ring and would enhance the intramolecular OH/π interaction through the electrostatic interaction.

DOI： 10.1063/5.0184664

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Proton transfer (PT) is one of the most ubiquitous reactions in chemistry and life science. The unique nature of PT has been rationalized not by a transport of a solvated...

DOI： 10.1039/d3sc05455a

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpca.3c02783

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/cphc.202300172

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpclett.3c01030

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpclett.2c03366

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Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/bcsj.20220345

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Language：English  

DOI： 10.26434/chemrxiv-2023-qn9rc

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

The magnesium channel controls Mg²⁺ concentration in the cell and plays an indispensable role in biological functions. The crystal structure of the Magnesium Transport E channel suggested that Mg²⁺ hydrated...

DOI： 10.1039/d3cp00992k

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpclett.2c02814

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.cplett.2022.140014

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/cphc.202200561

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpca.2c03789

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/jacs.2c04064

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/D2CP00543C

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

The infrared (IR) spectra of gas phase protonated nicotine has been measured in the never-before probed N–H “fingerprint region” (3200–3500 cm⁻¹).

DOI： 10.1039/d1cp05175j

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Valinomycin (VM) is a natural K⁺-selective ionophore that transports K⁺ through the cell membrane. VM captures K⁺ in its central cavity with a C₃-symmetric β-turn-like backbone. Although the binding affinity...

DOI： 10.1039/d2cp04570b

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Para-aminobenzoic acid (PABA) is a benchmark molecule to study solvent-induced proton site switching. Protonation of the carboxy and amino groups of PABA generates O- and N-protomers of PABAH⁺, respectively. Ion...

DOI： 10.1039/d2cp04497h

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Protonation sites in hydrated clusters can be clearly determined by CAS-IRPD (collision-assisted stripping infrared photodissociation) spectroscopy as shown for the example of hydrated protonated benzocaine.

DOI： 10.1039/d1cp05762f

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

K⁺ channels allow selective permeation of K⁺, but not physiologically abundant Na⁺, at almost diffusion limit rates. The conduction mechanism of K⁺ channels is still controversial, with experimental and computation...

DOI： 10.1039/d2cp01667b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AVS Science and Technology Society  

The performance of semiconductor devices has been improved by the miniaturization and the adoption of various materials. Together with this improvement, it has become difficult to measure the amount of injected impurities to control the electrical conductivity under the three-dimensional microstructure. As the volume decreases, the lower limit of the concentration that can be defined increases. In a 10-nm cubic region of silicon, there are approximately 64 000 atoms. One atom is approximately 16 ppm, and concentrations below that level cannot be defined. The limitation on the measurement accuracy of the PN junction position becomes unclear. Generally, the electrical characteristics of a semiconductor device are determined by the position of the PN junction and the concentrations in the P and N regions. In this paper, we elucidate the interface state of a minute PN junction. Based on the above, we will examine the lowest extent to which the concentration of impurities can be measured in a microvolume, with the current physical analysis technology, assuming ideal measurement conditions without any disturbance. Finally, we measure the sensitivity improvement of mass spectrometry using postionization technology with a femtosecond pulse infrared laser and demonstrate that it is possible to improve the performance of the impurity measurement.

DOI： 10.1116/6.0001244

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Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

DOI： 10.1063/5.0066919

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpca.1c06440

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpclett.0c03372

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Potassium channels allow K⁺ to rapidly diffuse, while the selectivity filter (SF) actively blocks Na⁺. The presence of water in the SF during ion translocation remains under debate due the...</p>

DOI： 10.1039/d1cp00936b

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>A general model of excited state hydrogen transfer (ESHT) which unifies ESHT and the excited state proton transfer (ESPT) is presented from experimental and theoretical works on phenol–(NH₃)<italic>n</italic>. The hidden role of ESPT is revealed.</p>

DOI： 10.1039/d0sc06877b

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Language：English   Publishing type：Research paper (scientific journal)  

IR super-resolution imaging of the cross section of the rachis of an avian feather was carried out by using a vibrational sum-frequency generation (VSFG) detected IR microscope with a sub-micrometer spatial resolution. In the YYX polarization combination, we clearly observed strong signals in the entire region of the rachis at the amide I vibration of β-keratin. On the other hand, the signal disappears from most of the cross section in the XXY polarization combination. Because the VSFG imaging detects the signal only from the interface, we conclude that the interfacial deflection inside of a rachis was detected.

DOI： 10.1016/j.bpc.2020.106482

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Cryogenic ion spectroscopy (CIS) was applied to singly protonated DYYVVR, a tryptic peptide that contains the two active tyrosine residues (Y980 and Y981) of the Janus kinase 3 (JAK3) kinase domain, together with its point mutants (Y980F and Y981F) and phosphorylated peptides (pY980, pY981, and pY980pY981). The two tyrosine chromophores showed distinguishable UV absorption bands at around 35 200 and 35 450 cm-1, respectively. By comparing with the point mutants, the lower electronic band was assigned to the absorption of Y981, and the higher one was assigned to Y980. When phosphorylated, the UV absorption of the phosphorylated chromophore shifts to higher energy above 36 500 cm-1 but the unphosphorylated chromophore gives the absorption in the same region. Conformer-specific IR spectroscopy and density functional theory (DFT) calculations were used to tentatively assign the structure of DYYVVR. Two conformations were found, where Y981 is solvated by the protonated side chain of arginine R984, and the orientation of the carboxylic OH of D979 was different between the two. It is demonstrated that CIS can be used to distinguish the two tyrosine chromophores and to locate the phosphorylation site of a kinase domain.

DOI： 10.1021/acs.jpclett.0c01802

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-VCH Verlag  

The infrared (IR) spectra of alkali and alkaline earth metal ion complexes with the Ac-Tyr-NHMe (GYG) peptide have been measured by laser photodissociation in a cold ion trap coupled with an electrospray mass spectrometer. The GYG peptide corresponds to a portion of the ion selectivity filter in the KcsA K+ channel that allows K+ to pass, but blocks Na+ even though it has a smaller ionic radius than K+. This current study extends a previous investigation on Na+ and K+ to the entire set of alkali metaI ions and alkaline earth dications. IR-IR hole-burning (IR2 dip) spectroscopy has established the coexistence of several conformers of the GYG-metal ion complexes. The structures of the conformers were assigned by comparison between the isomer-selected IR spectra and theoretical IR spectra obtained from quantum chemical calculations. It was found that the structure of the dominant conformer correlates with the ability of the ion to permeate through the K+ channel.

DOI： 10.1002/cphc.202000033

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NLM (Medline)  

The front cover artwork is provided by Takashi Tsujino (Science Graphics Co., Ltd.) . The image shows the efficacy of a bottom-up approach to ion selectivity of K+ channels. The GYG-K+ complex, which replicates the local portion of K+ channels, has three conformations with an equivalent distribution. Read the full text of the Article at 10.1002/cphc.202000033.

DOI： 10.1002/cphc.202000246

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PubMed

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1116/6.0000088

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Excited state proton transfer is the main non radiative deactivation process in protonated adrenaline.</p>

DOI： 10.1039/d0cp01127d

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Intersystem crossing from ¹πσ* to ³πσ* states traps excited state hydrogen transfer reaction in a bound state formed by ³ππ* and ³πσ* states.</p>

DOI： 10.1039/c9cp06369b

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Cryogenic ion trap infrared spectroscopy reveals that different binding motifs between the two enantiomers of protonated tyrosine and permethylated β-cyclodextrin result in chiral discrimination.</p>

DOI： 10.1039/d0cp02968h

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpca.9b04460

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Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C8FD00186C

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Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpclett.9b00184

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Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C8CP05839C

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Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C8CP05855E

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Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chemphys.2018.08.004

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Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C8CP02106F

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-VCH Verlag  

Receptor–neurotransmitter molecular recognition is key for neurotransmission. Although crystal structures of the receptors are known, the mechanism for recognition is not clear. Reported here is the ultraviolet (UV) and infrared (IR) spectra of complexes between a partial peptide (SIVSF), mimicking the binding motif of a catechol ring in the adrenergic receptor, and various ligands. The UV spectra show that two isomers coexist in the complex of SIVSF with properly recognized ligands, such as protonated adrenaline (adrenalineH+). From IR spectra, they are assigned to catechol- and amino-bound structures. The catechol-bound structure is not observed when the ligand is replaced by nonproper molecules, such as noradrenalineH+. The results suggest that SIVSF not only recognizes the catechol ring but can distinguish differences in the amine side chain. The method provides a new possibility for screening molecules as potential therapeutics for activating the receptor.

DOI： 10.1002/anie.201712976

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AVS Science and Technology Society  

Secondary-ion mass spectrometry (SIMS) sputter depth profiling is used for the quantitative depth profile analysis of impurities. However, SIMS suffers from a large quantitative uncertainty and depth-scale uncertainty at the interfaces of heteromultilayers and in the near-surface region, because the secondary ion yield and sputtering yield are significantly influenced by matrix effects and accumulation effects of the primary ion. In this paper, the authors report on the development of a new depth profiling method with good depth-scale accuracy and low matrix effects to overcome these problems. This was achieved through the combination of high-spatial-resolution bevel depth profiling and sputtered neutral mass spectrometry with laser postionization (laser-SNMS). The sample used to evaluate this new bevel depth profiling method was a silicon on insulator wafer obtained using the separation by implantation of oxygen technique and implanted with boron. Depth profiles were obtained using both SIMS and laser-SNMS and evaluated by comparison with the stopping and range of ions in matter (SRIM) simulation. Although both methods afforded quite good depth resolutions, in SIMS the secondary ion signal intensity for boron was amplified by the influence of the matrix effect and showed a discontinuous profile shape at the interfaces, whereas the profile for boron obtained using laser-SNMS was consistent with the SRIM results and exhibited high continuity. By using a combination of the bevel depth profiling method and laser-SNMS method, it was confirmed that an easy-to-analyze depth profile could be obtained for the dopant concentration in multilayer samples, which is difficult to obtain using the conventional SIMS method.

DOI： 10.1116/1.5019692

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AVS Science and Technology Society  

The element and/or material dependence of the useful yield in laser-ionization sputtered neutral mass spectrometry (SNMS) using a high-photon-flux laser was investigated. Useful yields obtained from Si, B, As, and O in Si and SiO2 matrices using both secondary ion mass spectrometry (SIMS) and SNMS were compared, and the possibility of the accurate analysis of impurities in multilayers was investigated in terms of tunnel ionization. The behavior of atoms released from the surface by ion bombardment was calculated, and it was considered that the flying speed of sputtered atoms depends on the mass and that this causes the elemental difference in the fractions of laser-irradiated atoms. In the case of SNMS, excluding O, whose ionization probability is considered to be much lower than for the other elements, the useful yields of Si, B, and As are within 1 order of magnitude in both the Si and SiO2 matrices, and the difference between the matrices for each element is within a factor of two. These differences are much smaller than in the result of SIMS. It was confirmed that the distribution of B in a SiO2/Si stacked layer can be analyzed more accurately by SNMS than by SIMS. SNMS with a high-photon-density laser is considered to be effective for the analysis of more than one element in multilayers.

DOI： 10.1116/1.5018092

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Consolidated knowledge of conformation and stability of amino acids and their clusters is required to understand their biochemical recognition. Often, alkali ions interact with amino acids and proteins. Herein, infrared photodissociation (IRPD) spectra of cryogenic metalated glutamic acid ions (GluM+, M = Li-Cs) are systematically analyzed in the isomer-specific fingerprint and XH stretch ranges (1100-1900, 2600-3600 cm-1) to provide a direct measure for cation-size-dependent conformational locking. GluM+ ions are generated by electrospray ionization and cooled down to 15 K in a cryogenic quadrupole ion trap. The assignment of the IRPD spectra is supported by density functional theory calculations at the dispersion-corrected B3LYP-D3/aug-cc-pVTZ level. In the global minimum of GluM+, the flexibility of Glu is strongly reduced by the formation of rigid ionic CO···M+···OC metal bridges, corresponding to charge solvation. The M+ binding energy decreases monotonically with increasing cation size from D0 = 314 to 119 kJ/mol for Li-Cs. Whereas for Li and Na only the global minimum of GluM+ is observed, for K-Cs at least three isomers exist at cryogenic temperature. The IRPD spectra of cold GluM+ ions are compared to IR multiple-photon dissociation spectra measured at room temperature. Furthermore, we elucidate the differences of the impact of protonation and metalation on the structure and conformational locking of Glu.

DOI： 10.1021/acs.jpcb.7b12601

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/c8cp90010h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

The structure and activity of peptides and proteins strongly rely on their charge state and the interaction with their hydration environment. Here, infrared photodissociation (IRPD) spectra of size-selected microhydrated clusters of cationic acetanilide (AA+, N-phenylacetamide), AA+-(H2O)n with n ≤ 3, are analysed by dispersion-corrected density functional theory calculations at the ωB97X-D/aug-cc-pVTZ level to determine the stepwise microhydration process of this aromatic peptide model. The IRPD spectra are recorded in the informative X-H stretch (νOH, νNH, νCH, amide A, 2800-3800 cm-1) and fingerprint (amide I-II, 1000-1900 cm-1) ranges to probe the preferred hydration motifs and the cluster growth. In the most stable AA+-(H2O)n structures, the H2O ligands solvate the acidic NH proton of the amide by forming a hydrogen-bonded solvent network, which strongly benefits from cooperative effects arising from the excess positive charge. Comparison with neutral AA-H2O reveals the strong impact of ionization on the acidity of the NH proton and the topology of the interaction potential. Comparison with related hydrated formanilide clusters demonstrates the influence of methylation of the amide group (H → CH3) on the shape of the intermolecular potential and the structure of the hydration shell.

DOI： 10.1039/c7cp04659f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Geometries and infrared (IR) spectra in the mid-IR region of phenol-(ammonia)n (PhOH-(NH3)n) (n = 0-10) clusters have been studied using density functional theory (DFT) to investigate the critical number of solvent molecules necessary to promote ground-state proton transfer (GSPT). For n ≤ 8 clusters, the most stable isomer is a non-proton-transferred (non-PT) structure, and all isomers found within 1.5 kcal mol-1 from it are also non-PT structures. For n = 9, the most stable isomer is also a non-PT structure
however, the second stable isomer is a PT structure, whose relative energy is within the experimental criterion of population (0.7 kcal mol-1). For n = 10, the PT structure is the most stable one. We can therefore estimate that the critical size of GSPT is n = 9. This is confirmed by the fact that these calculated IR spectra are in good accordance with our previous experimental results of mid-IR spectra. It is demonstrated that characteristic changes of the ν9a and ν12 bands in the skeletal vibrational region provide clear information that the GSPT reaction has occurred. It was also found that the shortest distance between the π-ring and the solvent moiety is a good indicator of the PT reaction.

DOI： 10.1039/c7cp05247b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Solvation plays an essential role in controlling the mechanism and dynamics of chemical reactions in solution. The present study reveals that changes in the local solute-solvent interaction have a great impact on the timescale of solvent rearrangement dynamics. Time-resolved IR spectroscopy has been applied to a hydration rearrangement reaction in the monohydrated 5-hydroxyindole-water cluster induced by photoionization of the solute molecule. The water molecule changes the stable hydration site from the indolic NH site to the substituent OH site, both of which provide a strongly attractive potential for hydration. The rearrangement time constant amounts to 8 ± 2 ns, and is further slowed down by a factor of more than five at lower excess energy. These rearrangement times are slower by about three orders of magnitude than those reported for related systems where the water molecule is repelled from a repulsive part of the interaction potential toward an attractive well. The excess energy dependence of the time constant is well reproduced by RRKM theory. Differences in the reaction mechanism are discussed on the basis of energy relaxation dynamics.

DOI： 10.1039/c7cp06127g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Most biochemical processes occur in aqueous solution. Here, we characterize the initial microhydration steps of the 5-hydroxyindole cation (5HI+) in its 2A′′ ground electronic state by infrared photodissociation (IRPD) spectroscopy of 5HI+-Wn-Lm clusters (W = H2O, L = Ar and N2, n ≤ 4, m ≤ 2) in a molecular beam and dispersion-corrected density functional theory calculations (B3LYP-D3/aug-cc-pVTZ). Characteristic size- and isomer-dependent XH stretch frequencies (X = O, N) of 5HI+-Wn reveal information about the preferred cluster growth and solvation energies. The IRPD spectrum of 5HI+-W is a superposition of the spectra of two isomers, in which W is H-bonded to the acidic NH or OH group, whereby OH⋯W hydrogen-bonds (H-bonds) are stronger than NH⋯W H-bonds. Spectra of larger 5HI+-Wn clusters (n ≥ 2) elucidate the competition between interior ion solvation and the formation of H-bonded water networks. The nature and strengths of the competing H-bonds are quantified by the noncovalent interaction approach. Comparison to results for neutral 5HI-W and 5HI+-Ln clusters with nonpolar ligands reveals the effects of ionization and ligand type on the intermolecular interaction potential and cluster growth. Comparison to corresponding microhydrated clusters of the phenol, indole, and pyrrole cations illustrates the effects of substitution of functional groups and addition of aromatic rings on the hydration process.

DOI： 10.1039/c7cp06132c

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-VCH Verlag  

Excited-state hydrogen transfer (ESHT) is responsible for various photochemical processes of aromatics, including photoprotection of nuclear basis. Its mechanism is explained by internal conversion from the aromatic ππ* to πσ* states via conical intersection. This means that the electron is transferred to a diffuse Rydberg-like σ* orbital apart from proton migration. This picture means the electron and the proton do not move together and the dynamics are different in principle. Here, we have applied picosecond time-resolved near-infrared (NIR) and infrared (IR) spectroscopy to the phenol-(NH3)5 cluster, the benchmark system of ESHT, and monitored the electron transfer and proton motion independently. The electron transfer monitored by the NIR transition rises within 3 ps, while the overall H transfer detected by the IR absorption of NH vibration appears with a lifetime of about 20 ps. This clearly proves that the electron motion and proton migration are decoupled. Such a difference of the time-evolutions between the NIR absorption and the IR transition has not been detected in a cluster with three ammonia molecules. We will report our full observation together with theoretical calculations of the potential energy surfaces of the ππ* and πσ* states, and will discuss the ESHT mechanism and its cluster size-dependence between n=3 and 5. It is suggested that the presence and absence of a barrier in the proton transfer coordinate cause the different dynamics.

DOI： 10.1002/chem.201704129

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

To understand the role of chirality in shaping biological supramolecular systems it is instructive to visualize the subtle effects of stereochemistry on the structure of model aggregates at the molecular level. Here, we apply conformer-specific IR-UV double-resonance laser spectroscopy in a cold ion trap to derive a detailed description of the protonated homodimers of (1R,2S)-cis- and (1R,2R)-trans-1-amino-2-indanol (c-AI2H+, t-AI2H+). Although the protonated monomers (c-AIH+, t-AIH+) only differ by the chirality of one carbon atom, their conformations are clearly distinct. c-AIH+ has an intramolecular NH+⋯O hydrogen bond (H-bond), while t-AIH+ lacks such an interaction. This has crucial consequences on the geometry and stability of the corresponding c-AI2H+ and t-AI2H+ dimers. While there is a competition between intra- and intermolecular H-bonds in c-AI2H+, the formation of t-AI2H+ does not require deformation of the monomers. This difference results in higher binding energies of t-AI2H+ compared to c-AI2H+. To optimize the H-bond network, the two dimers do not necessarily involve the corresponding most stable monomers. c-AI2H+ and t-AI2H+ differ in their UV photodissociation mass spectra and in their electronic spectra, which suggests different geometries also in the excited state.

DOI： 10.1039/c8cp00787j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We applied infrared (IR) spectroscopy on electronic excited states of a benzene dimer (Bz(2)) isolated in a supersonic expansion to investigate the vibrational structure and geometry of the excimer (EXC) state where the electronic excitation is equally shared between the two Bz units. The IR spectrum of an EXC produced via the electronic origin of Bz(2) gives a simpler spectral appearance than that in the electronic ground state, in which it has a T-shaped structure. Each band position locates nearly at the average of the corresponding vibrations in the electronic ground and excited states of the Bz monomer. This frequency averaging is explained by an excitation exchange model that takes into account vibrational excitations. From the observed frequency averaging, a highly symmetric parallel stacking structure in the EXC state is concluded with the help of a DFT calculation. This model clarifies that Franck-Condon factors between the S-1-S-0 transition of the monomer govern not only the magnitude of the EXC interaction, but also the configuration of vibrational states. The IR spectrum of the vibrationally excited EXC state produced by excitation to the 6(1) level of the stem site, on the other hand, shares the IR features both of the EXC state and the local excited (LE) state in which the excitation localizes on one of the benzene rings, making a T-shape contact. The structural interconversion equilibrium between parallel stacking (EXC) and T-shaped (LE) structures due to the vibrational excess energy has been established.

DOI： 10.1039/c7cp03480f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Most proteins work in aqueous solution and the interaction with water strongly affects their structure and function. However, experimentally the motion of a specific single water molecule is difficult to trace by conventional methods, because they average over the heterogeneous solvation structure of bulk water surrounding the protein. Here, we provide a detailed atomistic picture of the water rearrangement dynamics around the -CONH- peptide linkage in the two model systems formanilide and acetanilide, which simply differ by the presence of a methyl group at the peptide linkage. The combination of pico-second pump-probe time-resolved infrared spectroscopy and molecular dynamics simulations demonstrates that the solvation dynamics at the molecular level is strongly influenced by this small structural difference. The effective timescales for solvent migration triggered by ionization are mainly controlled by the efficiency of the kinetic energy redistribution rather than the shape of the potential energy surface. This approach provides a fundamental understanding of protein hydration and may help to design functional molecules in solution with tailored properties.

DOI： 10.1039/c7cp03992a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The conformer-selected ultraviolet (UV) and infrared (IR) spectra of protonated noradrenaline were measured using an electrospray/cryogenic ion trap technique combined with photo-dissociation spectroscopy. By comparing the UV photo dissociation (UVPD) spectra with the UV-UV hole burning (HB) spectra, it was found that five conformers coexist under ultra-cold conditions. Based on the spectral features of the IR dip spectra of each conformer, two different conformations on the amine side chain were identified. Three conformers (group I) were assigned to folded and others (group II) to extended structures by comparing the observed IR spectra with the calculated ones. Observation of the significantly less-stable extended conformers strongly suggests that the extended structures are dominant in solution and are detected in the gas phase by kinetic trapping. The conformers in each group are assignable to rotamers of OH orientations in the catechol ring. By comparing the UV-UV HB spectra and the calculated Franck-Condon spectra obtained by harmonic vibrational analysis of the S-1 state, with the aid of relative stabilization energies of each conformer in the S-0 state, the absolute orientations of catechol OHs of the observed five conformers were successfully determined. It was found that the 0-0 transition of one folded conformer is red-shifted by about 1000 cm(-1) from the others. The significant red-shift was explained by a large contribution of the pi sigma* state to S-1 in the conformer in which an oxygen atom of the meta-OH group is close to the ammonium group.

DOI： 10.1039/c6cp08426e

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Recognition properties of biologically relevant molecules depend on their conformation. Herein, the conformation of protonated glutamic acid (H(+)Glu) isolated in quadruple ion traps is characterized by vibrational spectroscopy at room and cryogenic temperatures and dispersion-corrected density functional theory calculations at the B3LYP-D3/aug-cc-pVTZ level. The infrared multiple photon dissociation (IRMPD) spectrum recorded in the fingerprint range at room temperature using an IR free electron laser is attributed to the two most stable and nearly isoenergetic conformations (1-cc and 2-cc) with roughly equal population (Delta G(298) = 0.0 kJ mol(-1)). Both have bridging C=O. . . (HNH)(+). . .O=C ionic H-bonds of rather different strengths but cannot be distinguished by their similar IRMPD spectra. In contrast, the higher-resolution single-photon IRPD spectrum of H-2-tagged H+ Glu recorded in the conformation-sensitive X-H stretch range in a trap held at 10 K distinguishes both conformers. At low temperature, 1-cc is roughly twice more abundant than 2-cc, in line with its slightly lower calculated energy (Delta E-0 = 0.5 kJ mol(-1)). This example illustrates the importance of cryogenic cooling, single-photon absorption conditions, and the consideration of the X-H stretch range for the identification of biomolecular conformations involving hydrogen bonds.

DOI： 10.1039/c6cp08553a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

The cooling efficiency of a cryogenic three-dimensional quadrupole ion trap (QIT) is drastically improved by using copper electrodes instead of conventional stainless-steel ones. The temperature of trapped ions (protonated tyrosine TyrH(+) was estimated based on the ultraviolet (UV) photo-dissociation spectra. The UV spectrum of TryH(+) shows almost no hot bands, and thus the high cooling efficiency of the copper ion trap was proven. The temperature was also estimated by simulating the observed band contour in the UV spectra, which is determined by the population in the rotationally excited levels. From the simulations, the temperature of TryH(+) was estimated to be similar to 13 K, while that in the stainless-steel QIT was 45-50 K. In addition, to demonstrate the advantage of the copper QIT, UV-UV hole burning (HB) spectra, i.e. conformation-selected UV spectra, were measured. It was confirmed that four different conformers, A similar to D, coexist in the ultra-cold protonated tyrosine. By comparing with the calculated Franck-Condon spectra, their structural assignments were discussed, including the orientation of the OH group. (C) 2016 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jms.2016.10.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

An accurate theoretical prediction of the vibrational spectrum of polypeptides remains to be a challenge due to (1) their conformational flexibility and (2) non negligible anharmonic effects. The former makes the search for conformers that contribute to the spectrum difficult, and the latter requires an expensive, quantum mechanical calculation for both electrons and vibrations. Here, we propose a new theoretical approach, which implements an enhanced conformational sampling by the replica-exchange molecular dynamics method, a structural clustering to identify distinct conformations, and a vibrational structure calculation by the second-order vibrational quasi-degenerate perturbation theory (VQDPT2). A systematic mode-selection scheme is developed to reduce the cost of VQDPT2 and the generation of a potential energy surface by the electronic structure calculation. The proposed method is applied to a pentapeptide, SIVSF-NH2, for which the infrared spectrum has recently been measured in the gas phase with high resolution in the OH and NH stretching region. The theoretical spectrum of the lowest energy conformer is obtained with a mean absolute deviation of 11.2 cm(-1) from the experimental spectrum. Furthermore, the NH stretching frequencies of the five lowest energy conformers are found to be consistent with the literature values measured for small peptides with a similar secondary structure. Therefore, the proposed method is a promising way to analyze the vibrational spectrum of polypeptides.

DOI： 10.1021/acs.jpcb.6b06672

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Laser desorption supersonic jet laser spectroscopy has been applied to a penta-peptide, Ser-Ile-Val-Ser-Phe-NH2 (SIVSF-NH2), which is a partial sequence of a binding site in a beta(2)-adrenaline receptor protein. By comparing the resonance enhanced multiphoton ionization spectrum with the ultraviolet-ultraviolet hole burning (HB) spectrum, it is concluded that only a single conformer exists. The infrared (IR) spectrum of the X-H stretching region, measured by IR dip spectroscopy, shows that all of the OH and NH groups form hydrogen bonds. The structure of SIVSF-NH2 is assigned by the combination of a force field calculation (CONFLEX) and quantum chemical calculations both in S-0 and S-1. Over 20 000 stable conformations, given by CONFLEX, are classified into 6987 groups and 1068 groups in which all of the NH and OH bonds are hydrogen-bonded are selected. The most stable structure in each group was geometrically optimized by density functional theory (DFT) calculations, and theoretical IR spectra were calculated for the conformers for which the energies are within 10 kJ mol(-1) of the most stable one. It has been found that the most stable and the secondmost stable conformers well-reproduce the observed IR spectrum. The vibrational frequencies in S-1 were also calculated for these two conformers. According to the reproduction of the vibrational frequencies in the HB spectrum, the structure of SIVSF-NH2 is assigned to the most stable conformer, which forms a hydrogen-bonded structure corresponding to a compact, distorted version of the beta hairpin of peptides and proteins.

DOI： 10.1039/c6cp04196e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The geometries of 1-naphthol-(ammonia)(n) (1-NpOH-(NH3)(n)) (n = 6-9) clusters have been calculated by using the density functional theory (DFT) to investigate ground-state proton transfer (GSPT). For n &lt;= 7 clusters, the most stable isomer is a non-proton-transferred (non-PT) structure, and isomers within 1.4 kcal/mol unstable from it were also non-PT structures. For n = 8 and 9, the most stable isomer is also a non-PT structure; however, the second stable isomer is the PT structure, of which the relative energy is within 0.5 kcal/mol. We therefore concluded that the threshold size of GSPT is n = 8 under the conventional experimental condition. It is also found that the minimal distance between the pi-ring and the solvent moiety is a good indicator of the PT reaction. This suggests that the solvation of the pi-ring is important to trigger the PT reaction.

DOI： 10.1021/acs.jpca.6b07079

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Language：English   Publisher：AMER CHEMICAL SOC  

Solvation processes play a crucial role in chemical reactions and biomolecular recognition phenomena. Although solvation dynamics of interfacial or biological water has been studied extensively in aqueous solution, the results are generally averaged over several solvation layers and the motion of individual solvent molecules:is difficult to capture. This review describes the development and application of a new experimental approach, namely, picosecond time-resolved pump-probe infrared spectroscopy of size- and isomer-selected aromatic clusters, in which for the first time the dynamics of a single individual solvent molecule can be followed in real time. The intermolecular isomerization reaction is triggered by resonant photoionization (pump), and infrared phatodissociation (probe) at variable delay generates the spectroscopic signature of salient properties of the reaction, including rates, yields, pathways; branching ratios of competing reactions, existence of reaction intermediates, occurrence of back reactions; and time scales of energy relaxation processes. It is shown that this relevant information can reliably be decoded from the experimental spectra by sophisticated molecular dynamics simulations. This review covers a description of the experimental strategies and spectroscopic methods along with all applications to date, which range from aromatic clusters with nonpolar solvent molecules to aromatic monohydrated biomolecule.

DOI： 10.1021/acs.chemrev.5b00610

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The ultrafast deactivation processes in the excited state of biomolecules, such as the most stable tautomers of guanine, forbid any state-of-the-art gas phase spectroscopic studies on these species with nanosecond lasers. This drawback can be overcome by grafting a chromophore having a long-lived excited state to the molecule of interest, allowing thus a mass-selective detection by nanosecond R2PI and therefore double resonance IR/UV conformer-selective spectroscopic studies. The principle is presently demonstrated on the keto form of a modified 9-methylguanine, for which the IR/UV double resonance spectrum in the C=O stretch region, reported for the first time, provides evidence for extensive vibrational couplings within the guanine moiety. Such a successful strategy opens up a route to mass-selective IR/UV spectroscopic investigations on molecules exhibiting natural chromophores having ultrashort-lived excited states, such as DNA bases, their complexes as well as peptides containing short-lived aromatic residues.

DOI： 10.1021/acs.jpca.6b01194

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Vibronic and vibrational spectra of 2-(2-fluoro-phenyl)-ethylamine (2-FPEA) conformers were measured in a molecular beam by resonant two-photon ionization (R2PI), ultraviolet-ultraviolet hole burning (UV-UV HB) spectroscopy, and ionization-loss stimulated Raman spectroscopy (ILSRS). The measured ILSR spectral signatures in the survey spectra of the amino group region and in the broad spectral range revealed the presence of five different conformers, which were confirmed by the HB spectra. The determination of the structures of the conformers of 2-FPEA was assisted by quantum chemical calculations of the torsional potential energy surface and of the scaled harmonic Raman spectra. Comparison of the measured ILSR spectra with the calculated Raman spectra allowed us to identify one gauche structure with the ethylamino side chain folded toward the fluorine atom, two gauche structures with the ethylamino side chain folded to the opposite side and two anti conformers with extended tails. The effect of fluorination on the spectra and on the stability and structures of these species is discussed.

DOI： 10.1039/c5cp06131h

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The ionization-induced pi &lt;-&gt; H site switching reaction in phenol(+)-Rg (PhOH+-Rg) dimers with Rg = Ar and Kr is traced in real time by picosecond time-resolved infrared (ps-TRIR) spectroscopy. The ps-TRIR spectra show the prompt appearance of the non-vanishing free OH stretching band upon resonant photoionization of the pi-bound neutral clusters, and the delayed appearance of the hydrogen-bonded (H-bonded) OH stretching band. This result directly proves that the Rg ligand switches from the pi-bound site on the aromatic ring to the H-bonded site at the OH group by ionization. The subsequent H &lt;-&gt; pi back reaction converges the dimer to a pi &lt;-&gt; H equilibrium. This result is in sharp contrast to the single-step pi &lt;-&gt; H forward reaction in the PhOH+-Ar-2 trimer with 100% yield. The reaction mechanism and yield strongly depend on intracluster vibrational energy redistribution. A classical rate equation analysis for the time evolutions of the band intensities of the two vibrations results in similar estimates for the time constants of the pi &lt;-&gt; H forward reaction of tau(+) = 122 and 73 ps and the H &lt;-&gt; pi back reaction of tau_ = 155 and 188 ps for PhOH+-Ar and PhOH+-Kr, respectively. The one order of magnitude slower time constant in comparison to the PhOH+-Ar-2 trimer (tau(+) = 7 ps) is attributed to the decrease in density of states due to the absence of the second Ar in the dimer. The similar time constants for both PhOH+-Rg dimers are well rationalized by a classical interpretation based on the comparable potential energy surfaces, reaction pathways, and density of states arising from their similar intermolecular vibrational frequencies.

DOI： 10.1039/c6cp05016f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The gas phase structure and excited state dynamics of o-aminophenol-H2O complex have been investigated using REMPI, IR-UV hole-burning spectroscopy, and pump-probe experiments with picoseconds laser pulses. The IR-UV spectroscopy indicates that the isomer responsible for the excitation spectrum corresponds to an orientation of the OH band away from the NH2 group. The water molecule acts as H-bond acceptor of the OH group of the chromophore. The complexation of o-aminophenol with one water molecule induced all enhancement in the excited state lifetime on the band origin. The variation of the excited state lifetime of the complex with the excess energy from 1.4 +/- 0.1 ns for the 0-0 band to 0.24 +/- 0.3 ns for the band at 0-0 + 120 cm(-1) is very similar to the variation observed in the phenol-NH3 system. This experimental result suggests that the excited state hydrogen transfer reaction is the dominant channel for the non radiative pathway. Indeed, excited state ab initio calculations demonstrate that H transfer leading to the formation of the H3O center dot radical within the complex is the main reactive pathway.

DOI： 10.1021/acs.jpca.5b10142

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Hydrogen-release by photoexcitation, excited-state-hydrogen- transfer (ESHT), is one of the important photochemical processes that occur in aromatic acids and is responsible for photoprotection of biomolecules. The mechanism is described by conversion of the initial state to a charge-separated state along the O(N)-H bond elongation, leading to dissociation. Thus ESHT is not a simple H-atom transfer in which a proton and a 1s electron move together. Here we show that the electron-transfer and the proton-motion are decoupled in gas-phase ESHT. We monitor electron and proton transfer independently by picosecond time-resolved near-infrared and infrared spectroscopy for isolated phenol-(ammonia) 5, a benchmark molecular cluster. Electron transfer from phenol to ammonia occurred in less than 3 picoseconds, while the overall H-atom transfer took 15 picoseconds. The observed electron-proton decoupling will allow for a deeper understanding and control of of photochemistry in biomolecules.

DOI： 10.1002/anie.201506467

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The conformational structure of indole-3-carbinol (I3C) has been investigated in the gas phase for the first time using a laser desorption technique. A UV-UV hole-burning technique revealed the presence of a single conformer of I3C in the mass-selected resonant two-photon ionization spectrum. The assignment of the observed IR spectrum of I3C is inconclusive due to almost identically predicted IR frequencies of the two lowest energy conformers from harmonic calculations. A conclusive assignment for the conformer of I3C has been reported with an aid of performing anharmonic calculations and Franck-Condon simulations on the two lowest-energy conformers. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2015.08.063

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The geometries and energetics of the ground and lower-lying singlet excited states S-0, L-a, and L-b of 1-naphthol (NpOH)(NH3)(n) (n = 05) clusters have been computed using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Cluster size dependence of the excited state proton transfer (ESPT) reaction was investigated by the vertical transitions from the geometries that can be populated in the molecular beam experiments. For the n = 3 and 4 clusters, the proton-transferred geometries cannot be accessible without significant geometrical rearrangement from the initially populated isomers. For the n = 5 clusters, the proton-transferred structure is found in the L-a excited state of the isomer that can be populated in the beam. Thus, ESPT is possible by the optically prepared L-b state via internal conversion to L-a. We concluded that the threshold cluster size of ESPT is n = 5 under the experimental condition with low excess energy.

DOI： 10.1021/jp507222n

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Hydration of peptides and proteins has a strong impact on their structure and function. Infrared photodissociation spectra (IRPD) of size-selected clusters of the formanilide cation, FA(+)-(H2O)(n) (n=1-5), are analyzed by DFT calculations at the pi B97X D/aug-cc-pVTZ level to determine the sequential microhydration of this prototypical aromatic amide cation. IRPD spectra are recorded in the hydride stretch and fingerprint ranges to probe the preferred interaction motifs and the cluster growth. IRPD spectra of cold Ar-tagged clusters, FA(+)-(H2O)(n)-Ar, reveal the important effects of temperature and entropy on the observed hydration motifs. At low temperature, the energetically most stable isomers are prominent, while at higher temperature less stable but more flexible isomers become increasingly populated because of entropy. In the most stable structures, the H2O ligands form a hydrogen-bonded solvent network attached to the acidic NH proton of the amide, which is stabilized by large cooperative effects arising from the excess positive charge. In larger clusters, hydration bridges the gap between the NH and CO groups (n=4) solvating the amide group rather than the more positively charged phenyl ring. Comparison with neutral FA(+)-(H2O)(n) clusters reveals the strong impact of ionization on the acidity of the NH proton, the strength and topology of the interaction potential, and the structure of the hydration shell.

DOI： 10.1021/jp511421h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The structure of the phenol-argon cluster (PhOH-Ar) in high-n Rydberg states is investigated by the newly developed technique of mass analyzed threshold ionization detected infrared (MATI-IR) spectroscopy. This method selectively measures IR spectra of molecular clusters in very high-n Rydberg states (n &gt; 100) utilized in zero kinetic energy (ZEKE) photoelectron and MATI spectroscopy, whose ionic cores are essentially the same as the corresponding bare cation. The MATI-IR spectrum exhibits only the free OH stretching vibration (V-OH(pi)) when the pi-bound cluster of the neutral ground electronic state (S-0) is resonantly excited via the S-1 origin to Rydberg states converging to its adiabatic ionization energy level, IE0(pi). When Rydberg states converging to vibrationally excited levels of the local p-bound minimum are prepared, in addition to V-OH(pi) also the hydrogen-bonded OH stretching vibration (V-OH(H)) of the H-bonded global minimum is observed in the MATI-IR spectra, even for vibrational excitation of only 14 cm(-1) above IE0(pi). These results show that the pi -&gt; H site switching reaction of the Ar ligand from the aromatic ring to the OH group proceeds only from vibrationally excited states in the p-bound cation core with a small barrier of less than 14 cm(-1) from IE0(pi). On the other hand, directly photoionized PhOH+-Ar shows both V-OH(H) and V-OH(pi) in the IR spectra, even when it is just ionized to IE0(pi). This result implies that the ionization-induced pi -&gt; H site switching occurs without excess energy in the H-bound or pi-bound cations, in contrast to very high-n Rydberg states converging to levels of the pi-bound cation. The different efficiencies of the site switching for the Rydberg ion core and the bare ion and the mechanism for the pi -&gt; H site switching are interpreted by direct ionization from the pi-bound to the H-bound structures in addition to the conventional vertical ionization and transitions to high-n Rydberg states.

DOI： 10.1039/c4cp04584j

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The dynamics of a solvent is important for many chemical and biological processes. Here, the migration dynamics of a single water molecule is triggered by the photoionization of the 4-aminobenzonitrile-water (4ABN-W) cluster and monitored in real time by picosecond time-resolved IR (ps TRIR) spectroscopy. In the neutral cluster, water is hydrogen-bonded to the CN group. When this CN-bound cluster is selectively ionized with an excess energy of 1238 cm(-1), water migrates with a lifetime of tau = 17 ps from the CN to the NH2 group, forming a more stable 4ABN(+)-W(NH) isomer with a yield of unity. By decreasing the ionization excess energy, the yield of the CN -&gt; NH2 reaction is reduced. The relatively slow migration in comparison to the ionization-induced solvent dynamics in the related acetanilide-water cluster cation (tau = 5 ps) is discussed in terms of the internal excess energy after photoionization and the shape of the potential energy surface.

DOI： 10.1039/c5cp05400a

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The geometries of 1-naphthol-(piperidine)(n) (1-NpOH-(Pip)(n)) (n = 0-3) clusters have been calculated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to investigate excited-state proton transfer (ESPT) in the low-lying singlet excited states, L-a and L-b. For the n = 1 cluster, no PT structure was found in L-b and L-a as well as the ground state, S-0. For n = 2, optically accessible Lb from S-0 shows the PT structure. We therefore concluded that the threshold size of ESPT is n = 2, which is consistent with previous experimental results. ESPT in 1-NpOH-(Pip)(n) is simply triggered by optical excitation to L-b. It is essentially different from the 1-NpOH-(NH3)(n) cluster in which an internal conversion process is required to promote ESPT. From the calculated structures, the importance of the solvation of the pi-ring is strongly suggested rather than the proton affinity in ESPT.

DOI： 10.1039/c5cp03620h

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We observed the real-time excimer (EXC) formation dynamics of a gas phase benzene dimer (Bz(2)) cluster after photo-excitation to the S-1 state by applying an ionization detected picosecond transient absorption method for probing the visible EXC absorption for the first time. The time evolution of the EXC absorption from the S-1 0 degrees level shows a rise that is well fitted by a single exponential function with a time constant of 18 +/- 2 ps. The structure of the Bz dimer has a T-shaped structure in the ground electronic state, and that in the EXC state is a parallel sandwich (SW) structure. Thus, the observed rise time corresponds to the structural change from the T to the SW structures, which directly shows the EXC formation. On the other hand, the EXC formation after excitation of the S-1 6(1) vibrational level of the stem site showed a faster rise of the time constant of 10 +/- 2 ps. Supposing equilibrium between the EXC and the local excited states, it followed that the intramolecular vibrational energy redistribution rate of the 6(1) level is largely enhanced and becomes faster than the EXC formation reaction.

DOI： 10.1039/c5cp03010b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Conformer selected electronic and vibrational spectra of homophenylalanine, phenylalanine analogue molecule, were measured by UV-UV hole burning and IR dip spectroscopy combined with laser desorption technique. 10 conformers were found by UV-UV hole burning spectroscopy and their structures were assigned by IR dip and UV absorption spectra with aid of quantum chemical calculations in both S-0 and S-1. This study shows that the combination of simulated IR and UV spectra is powerful to assign flexible molecules. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chemphys.2014.10.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Infrared photodissociation (IRPD) spectra of mass-selected 4-aminobenzonitrile-(water)(n) cluster cations, ABN(+)-(H2O) n with n &lt;= 4, recorded in the N-H and O-H stretch ranges are analyzed by quantum chemical calculations at the M06-2X/aug-cc-pVTZ level to determine the evolution of the initial microhydration process of this bifunctional aromatic cation in its ground electronic state. IRPD spectra of cold clusters tagged with Ar and N-2 display higher resolution and allow for a clear-cut structural assignment. The clusters are generated in an electron impact source, which generates predominantly the most stable isomers. The IRPD spectra are assigned to single isomers for n = 1-3. The preferred cluster growth begins with sequential hydration of the two acidic NH protons of the amino group (n = 1-2), which is followed by attachment of secondary H2O ligands hydrogen-bonded to the first-shell ligands (n = 3-4). These symmetric and branched structures are more stable than those with a cyclic H-bonded solvent network. Moreover, in the size range n = 4 the formation of a solvent network stabilized by strong cooperative effects is favored over interior ion hydration which is destabilized by noncooperative effects. The potential of the ABN(+)-H2O dimer is characterized in detail and supports the cluster growth derived from the IRPD spectra. Although the N-H bonds are destabilized by stepwise microhydration, which is accompanied by increasing charge transfer from ABN(+) to the solvent cluster, no proton transfer to the solvent is observed for n &lt;= 4. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4901893

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The dynamics and energetics of water at interfaces or in biological systems plays a fundamental role in all solvation and biological phenomena in aqueous solution. In particular, the migration of water molecules is the first step that controls the overall process in the time domain. Experimentally, the dynamics of individual water molecules is nearly impossible to follow in solution, because signals from molecules in heterogeneous environments overlap. Although molecular dynamics simulations do not have this restriction, there is a lack of experimental data to validate the calculated dynamics. Here, we demonstrate a new strategy, in which the calculated dynamics are verified by measured time-resolved infrared spectra. The coexistence of fast and slow migrations of water molecules around a CONH peptide linkage is revealed for a model system representative of a hydrate peptide.

DOI： 10.1002/anie.201409047

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DOI： 10.1380/jsssj.35.383

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The gas phase structure of 2-aminophenol has been investigated using UV-UV as well as IR-UV hole burning spectroscopy. The presence of a free OH vibration in the IR spectrum rules out the contribution of the cis isomer, which is expected to have an intramolecular H-bond, to the spectra. The excited state lifetimes of different vibronic levels have been measured with pump-probe picosecond experiments and are all very short (35 +/- 5) Ps as compared to other substituted phenols. The electronic states and active vibrational modes of the cis and trans isomers have been calculated with ab initio methods for comparison with the experimental spectra. The Franck-Condon simulation of the spectrum using the calculated ground and excited state frequencies of the trans isomer is in good agreement with the experimental one. The very short excited state lifetime of 2-aminophenol can then be explained by the strong coupling between the two first singlet excited states due to the absence of symmetry, the geometry of the trans isomer being strongly nonplanar in the excited state.

DOI： 10.1021/jp411457v

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The dependence of the preferred microhydration sites of 4-aminobenzonitrile (4ABN) on electronic excitation and ionization is determined through IR spectroscopy of its clusters with water (W) in a supersonic expansion and through quantum chemical calculations. IR spectra of neutral 4ABN and two isomers of its hydrogen-bonded (H-bonded) 4ABN-W complexes are obtained in the ground and first excited singlet states (S-0, S-1) through IR depletion spectroscopy associated with resonance-enhanced multiphoton ionization. Spectral analysis reveals that electronic excitation does not change the H-bonding motif of each isomer, that is, H2O binding either to the CN or the NH site of 4ABN, denoted as 4ABN-W(CN) and 4ABN-W(NH), respectively. The IR spectra of 4ABN+-W in the doublet cation ground electronic state (D-0) are measured by generating them either in an electron ionization source (EI-IR) or through resonant multiphoton ionization (REMPI-IR). The EI-IR spectrum shows only transitions of the most stable isomer of the cation, which is assigned to 4ABN(+)-W(NH). The REMPI-IR spectrum obtained through isomer-selective resonant photoionization of 4ABNW( NH) is essentially the same as the EI-IR spectrum. The REMPI-IR spectrum obtained by ionizing 4ABN-W(CN) is also similar to that of the 4ABN(+)-W(NH) isomer, but differs from that calculated for 4ABN(+)-W(CN), indicating that the H2O ligand migrates from the CN to the NH site upon ionization with a yield of 100 %. The mechanism of this CN -&gt; NH site-switching reaction is discussed in the light of the calculated potential energy surface and the role of intracluster vibrational energy redistribution.

DOI： 10.1002/chem.201303321

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Language：Japanese   Publisher：アドコム・メディア  

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IR spectra of phenol-CH4 complexes generated in a supersonic expansion were measured before and after photoionization. The IR spectrum before ionization shows the free OH stretching vibration (v(OH)) and the structure of neutral phenol-CH4 in the electronic ground state (S-0) is assigned to a p-bound geometry, in which the CH4 ligand is located above the phenol ring. The IR spectrum after ionization to the cationic ground state (D-0) exhibits a red shifted v(OH) band assigned to a hydrogen-bonded cationic structure, in which the CH4 ligand binds to the phenolic OH group. In contrast to phenol-Ar/Kr, the observed ionization-induced pi -&gt; H migration has unity yield for CH4. This difference is attributed to intracluster vibrational energy redistribution processes.

DOI： 10.1039/c3cp53533a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Infrared photodissociation (IRPD) spectra of mass-selected cluster ions of acetanilide (N-phenylacetamide), AA(+)-L-n, with the ligands L = He (n = 1-2), Ar (n = 1-7), and N-2 (n = 1-10) are recorded in the hydride stretch (amide A, nu(NH), nu(CH)) and fingerprint (amide I-III) ranges of AA(+) in its (2)A '' ground electronic state. Cold AA(+)-L-n clusters are generated in an electron impact ion source, which predominantly produces the most stable isomer of a given cluster ion. Systematic vibrational frequency shifts of the N-H stretch fundamentals (nNH) provide detailed information about the sequential microsolvation process of AA(+) in a nonpolar (L = He and Ar) and quadrupolar (L = N-2) solvent. In the most stable AA(+)-L-n clusters, the first ligand forms a hydrogen bond (H-bond) with the N-H proton of trans-AA(+) (t-AA(+)), whereas further ligands bind weakly to the aromatic ring (pi-stacking). There is no experimental evidence for complexes with the less stable cis-AA(+) isomer. Quantum chemical calculations at the M06-2X/aug-cc-pVTZ level confirm the cluster growth sequence derived from the IR spectra. The calculated binding energies of D-e(H) = 720 and 1227 cm(-1) for H-bonded and D-e(pi) = 585 and 715 cm(-1) for p-bonded Ar and N-2 ligands in t-AA(+)-L are consistent with the observed photofragmentation branching ratios of AA(+)-L-n. Comparison between charged and neutral AA((+))-L dimers indicates that ionization switches the preferred ion-ligand binding motif from p-stacking to H-bonding. Electron removal from the HOMO of AA(+) delocalized over both the aromatic ring and the amide group significantly strengthens the C=O bond and weakens the N-H bond of the amide group.

DOI： 10.1039/c4cp00401a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We are presenting vibrationally selective pump-probe measurements of the first electronic excited-state (pi pi*) lifetime of jet-cooled neutral catechol (1,2-dihydroxybenzene). The lifetime of the 0-0 transition is very short (7 ps) as rationalized by the small pi pi*/pi sigma* gap calculated. However, the lifetimes implying higher out-of-plane vibrational levels are longer (similar to 11 ps). This emphasizes the role of the out-of-plane vibration in the pi pi*/pi sigma* coupling, not only in its nature, but also in the number of quanta.

DOI： 10.1021/jz402089m

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

IR-UV double resonance spectroscopy based on polarized laser schemes is developed in order to gain information on the orientations of vibrational transition dipole moments. Polarization dependence of IR band shape is presented for the two amino stretching modes of aniline.

DOI： 10.1246/cl.130425

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Aiming for the highly sensitive analysis of aromatic hydrocarbons in organic mixtures, selective ionization using an ultraviolet laser ionization technique was examined for the determination of sputtered neutral species on organic surfaces. The mass spectrum of a model mixture containing pyrene and n-alkane showed that only pyrene was ionized and detected, whereas a mass spectrum without laser irradiation, i.e. in the case of secondary ion mass spectrometry, was dominated by many n-alkane fragment peaks. This technique was applied for the detection of polyaromatic hydrocarbons adsorbed on diesel exhaust particles. Two kinds of polyaromatic hydrocarbons were clearly detected because many aliphatic fragment signals were suppressed by means of ultraviolet laser ionization. Copyright © 2013 John Wiley &amp
Sons, Ltd.

DOI： 10.1002/sia.5284

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KOREAN CHEMICAL SOC  

DOI： 10.5012/bkcs.2013.34.8.2241

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Blackwell Publishing Ltd  

The chemical composition and structure of fine aerosol particles with diameters of less than 1 μm were analyzed in the spring of 2011 at Fukue Island, Japan, using an aerosol quadrupole mass spectrometer (Q-AMS, Aerodyne Research, Inc.) and a time-of-flight secondary ion mass spectrometer (TOF-SIMS). The Q-AMS results were similar to those of previous studies conducted at the same location, suggesting that the composition we observed is typical of this site. Based on the TOF-SIMS results, we classified the fine aerosol particles into three types: Type A, in which sulfate was covered with organic matter (OM)
Type B, in which soil-containing particles with a diameter of 0.5 μm were associated with sulfate and OM
and Type C, in which black carbon (BC) and sulfate aggregates were associated with OM. During the observation period, the relative abundances of Type A, B, and C particles were 55%, 20%, and 25%, respectively. The structure, chemical composition, and the proportion of each type of particles provide information for a more representative particle model in radiative models. The relative abundance of Type C, i.e., BC-containing particles, is quite different to that in Tokyo, suggesting that Type C could be an indicator of transboundary air pollution, in this case from mainland China. Key Points Fine particles analyzed by TOF-SIMS and AMS Structure and chemical compositions were analyzed Fine particles were classified into three types © 2013. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/jgrd.50477

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The electronic excitation and infrared (IR) spectra of a capped tri-peptide, Z-PLG-NH2 (Z = benzyloxycarbonyl, P = Pro, L = Leu, G = Gly), were measured in the gas phase by using the laser desorption supersonic jet technique. By measuring an ultraviolet-ultraviolet hole burning spectrum, it was found that Z-PLG-NH2 has the maximum three conformers in the gas phase, but that the population is mainly distributed to a single conformation. Molecular dynamics simulations and density functional theory calculations well-reproduced the observed IR spectrum, except for splitting of the NH stretching bands by a beta-turn structure that corresponds to a global minimum structure. Anharmonic vibrational analysis by vibrational quasi-degenerate perturbation theory (VQDPT) successfully reproduced the anharmonic splitting, and confirmed the assignments. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chemphys.2012.12.038

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IR super-resolution images of cross sections of a human black hair were measured by using a home-made vibrational sum-frequency generation (VSFG) detected IR microscope in the 6-9 mu m region with a submicrometer spatial resolution. For the amide III band, the sample gave clear strong signals at the cortex area. This enabled us to measure the distribution of intermediate filaments, which have an alpha-helix based quaternary structure of keratin proteins in the hair. On the other hand, the VSFG signal disappeared completely when the amide I band was monitored by the same polarization of incident light. From the polarization dependence of VSFG, it is concluded that the alpha-helix of keratin proteins are well aligned along the axial direction in human hair. (C) 2013 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.chemphys.2013.02.016

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DOI： 10.1016/j.chemphys.2013.04.003

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DOI： 10.1016/j.chemphys.2013.04.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The chemical composition and structure of fine aerosol particles with diameters of less than 1 mu m were analyzed in the spring of 2011 at Fukue Island, Japan, using an aerosol quadrupole mass spectrometer (Q-AMS, Aerodyne Research, Inc.) and a time-of-flight secondary ion mass spectrometer (TOF-SIMS). The Q-AMS results were similar to those of previous studies conducted at the same location, suggesting that the composition we observed is typical of this site. Based on the TOF-SIMS results, we classified the fine aerosol particles into three types: Type A, in which sulfate was covered with organic matter (OM); Type B, in which soil-containing particles with a diameter of 0.5 mu m were associated with sulfate and OM; and Type C, in which black carbon (BC) and sulfate aggregates were associated with OM. During the observation period, the relative abundances of Type A, B, and C particles were 55%, 20%, and 25%, respectively. The structure, chemical composition, and the proportion of each type of particles provide information for a more representative particle model in radiative models. The relative abundance of Type C, i.e., BC-containing particles, is quite different to that in Tokyo, suggesting that Type C could be an indicator of transboundary air pollution, in this case from mainland China.

DOI： 10.1002/jgrd.50477

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Language：English   Publisher：ELSEVIER SCIENCE BV  

DOI： 10.1016/j.chemphys.2013.04.003

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The number of conformers and their structures of tyrosine are reassigned on the basis of resonance enhanced multiphoton ionization (REMPI), ultraviolet-ultraviolet hole burning (UV-UV HB), infrared (IR) dip spectra, and quantum chemical calculations. From comparison between REMPI and UV-UV HB spectra, it was found that 12 conformers coexist in the supersonic jet. The structures of these conformers are determined by the IR spectra and theoretical calculations. The number of conformers is more than that reported in the previous reports (8 conformers), and is rationalized by the systematic formation of conformers from simpler molecules without substituents, just like evolution. The importance of dipole-dipole interaction between an amino-acid chain and hydroxyl group at the benzene ring was also discussed. © 2013 The Owner Societies.

DOI： 10.1039/c3cp43573c

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IR photodissociation (IRPD) spectra of mass-selected cluster ions of 4-aminobenzonitrile (ABN+) with up to four Ar and N2 ligands are recorded over the spectral range of the N-H stretching vibrations (νs/a) of ABN+ in its 2B1 ground electronic state. ABN+-Ln clusters are produced in an electron impact cluster ion source, which predominantly generates the most stable isomer of a given cluster ion. Vibrational frequency shifts of νs/a provide information about the sequential microsolvation process of ABN+ in a nonpolar solvent. In ABN+-(N 2)n, the first two ligands fill a first subshell by forming hydrogen bonds to the acidic protons of the amino group, whereas further ligands bind more weakly to the aromatic ring (π bonds). Although the preferred cluster growth sequence in ABN+-Arn is similar, several isomers are observed because the hydrogen bonds are only slightly stronger than the π bonds. Quantum chemical calculations at the M06-2X/aug-cc-pVTZ level confirm the cluster growth sequence derived from the IR spectra and provide further details of the intermolecular potential. The calculated binding energies of D0(H)=532 and 895 cm-1 for hydrogen-bonded and D0(π)=512 and 530 cm-1 for π-bonded Ar and N2 ligands are consistent with the observed photofragmentation branching ratios. Comparison between ABN+-L n and the corresponding clusters with the aniline cation demonstrates that the NH protons of the amino group become slightly more acidic upon H→CN substitution at the para position. Comparison between charged and neutral ABN(+)-L dimers indicates that ionization switches the preferred ion-ligand binding motif from π to hydrogen bonding. Copyright © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

DOI： 10.1002/cphc.201200790

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Laser post-ionization of sputtered molecules by pulsed Ga focused ion-beam (Ga-FIB) bombardment was examined for the detection and imaging of polycyclic aromatic hydrocarbons (PAHs) on particles. As model samples, pyrene and pelyrene adsorbed on TiO2, blended regents of pyrene and n-heneicosan were used. The TiO2 particle size was selected to be several micro-meters. Laser light and Ga-FIB were synchronized with each other. The repetition rate synchronized with Ga-FIB was 1 kHz for pyrene analysis and 2 kHz for perylene, respectively. The laser wavelength was set to 266 nm. The wavelength was a generated fourth harmonic of a Nd:YAG DPSS (diode-pumped solid-state) micro-chip laser (UV microchip laser). By using a UV microchip laser, laser-SNMS (laser post-ionized sputtered neutral mass spectrometry) analysis and imaging were performed. The imaging of pyrene (m/z = 202, C16H10) and perylene (m/z = 252, C20H12) has been successful. Both the scanning ion microscopy image of TiO2 and the PAHs image in laser-SNMS analysis were well-fitted with each other.

DOI： 10.2116/analsci.29.291

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The S1S0 resonant enhanced multiphoton ionization (REMPI) spectrum as well as the infrared (IR) spectra in the S0 and S1 states of 4-aminobenzonitrile (4ABN) and its van der Waals complex with Ar (4ABNAr) were measured by means of IR depletion spectroscopy (REMPIIR). The IR spectrum of 4ABNAr in S0 shows symmetric and antisymmetric NH stretching vibrations (s and a) of the amino group at the same positions as those in the 4ABN monomer. This suggests that the Ar ligand locates above the benzene ring by van der Waals interactions (-bound). The same coincidence of vibrational frequencies was found in S1, and the -bound geometry was kept by the electronic excitation. The REMPIIR spectrum of 4ABN+Ar was also measured, and three major vibrational transitions were found. From the comparison to the IR dissociation spectrum with an electron impact source (EIIR), they were assigned to s, a and an NH-bending overtone of the -bound structure. It is concluded that photoionization of 4ABN+Ar does not promote site-switching of Ar from the -site to the H-site.

DOI： 10.1002/cphc.201200821

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

IR spectra of trans-1-naphthol-(H2O)(n) (n = 0-3) clusters in the S-1 state were measured by UV-IR fluorescence dip spectroscopy. The observed dip spectra were compared with theoretical ones of various stable conformations predicted by ab initio MO calculations. From the comparison, linear (n = 1) and cyclic hydrogen-bond structures (n = 2 and 3) were concluded. The relation between the structures and photochemical reactivity was discussed. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2012.11.030

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The infrared (IR) spectra of size-selected phenol-ammonia clusters, PhOH-(NH3)(n)(n &lt;= 11) in the 3-10 mu m wavelength region were measured to investigate the critical number of solvent molecules necessary to promote the ground state proton transfer (GSPT) reaction. While the N-H stretching vibrations did not provide clear information, characteristic changes that are assigned to the GSPT reaction were observed in the skeletal vibrational region. The production of phenolate anion (PhO-), which is a product of the GSPT reaction, was established from the appearance of characteristic bands assignable to C-C stretching and C-H bending vibrations of PhO- and from the corresponding disappearance of C-O-H bending vibration of PhOH at n = 9. The mid-IR spectroscopy directly proves the structural change induced by the deprotonation from the O-H bond and thus establishes the GSPT reaction as complete at n = 9. No such absorptions were observed for n 5 in line with a previous report. For n = 6-8, both the proton transferred and the nontransferred signatures were observed in the spectra, showing coexistence of both species for the first time.

DOI： 10.1021/jp312074m

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For many years, spatial resolution is the most critical problem in IR microspectroscopy. This is because the spatial resolution of a conventional infrared microscope is restricted by the diffraction limit, which is almost the same as the wavelength of IR light, ranging from 2.5 to 25 μm. In the recent years, we have developed two novel types of far-field IR super-resolution microscopes using 2-color laser spectroscopies, those are transient fluorescence detected IR (TFD-IR) spectroscopy and vibrational sum-frequency generation (VSFG) spectroscopy. In these ways, because both transient fluorescence and VSFG signal have a wavelength in the visible region, the image is observed at the resolution of visible light, which is about 10 times smaller than that of IR light (that is, IR super-resolution). By using these techniques, we can map the specific IR absorption band with sub-micrometer spatial resolution, visualization of the molecular structure and reaction dynamics in a non-uniform environment such as a cell becomes a possibility. In the present reviews, we introduce our novel IR super-resolution microspectroscopy and its application to single cells in detail. © 2013 Bentham Science Publishers.

DOI： 10.2174/138920113805219430

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Octopamine is a phenol analog of noradrenaline and acts as a neurotransmitter in invertebrates such as octopus. It is available as a hydrochloride salt to avoid air oxidation. We applied laser desorption supersonic jet technique to octopamine hydrochloride without any chemical preparations and found that molecular ion of octopamine, not salt, is observed. Resonanceenhanced 2-photon ionization and ultraviolet-ultraviolet holeburning spectra of octopamine were measured, and four conformers were identified. This number of conformations is rationalized by conformations of ethanolamine chain and orientations of phenolic OH. © 2013 The Chemical Society of Japan.

DOI： 10.1246/cl.130431

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Fine aerosol particles were analyzed by time-of-flight secondary ion mass spectrometry with high lateral resolution. After sulfate particles with a diameter of about 1 μm were sputtered by gallium primary ions (a gallium focused ion beam), solid materials with a diameter of about 100 nm were occasionally found inside the particles. Since the mass spectrum for the solid material was almost the same as that of graphite, we concluded that the solids were black carbon. It was also found that the black carbon located at the surface of the sulfate core, and they were usually surrounded by organic matter. © 2013,The Japan Society for Analytical Chemistry.

DOI： 10.2116/analsci.29.479

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The deactivation process of adenine excited near the band origin of the lowest ππ* state (1Lb) is investigated using picosecond (ps) time-resolved photoionization spectroscopy. The transients obtained with a ps pump pulse at the sharp vibronic bands, 36 105 cm -1 (D) and 36 248 cm-1 (E), in the resonant two-photon ionization spectrum exhibit a bi-exponential decay with two distinct time constants of τ1 ∼ 2 ps and τ2 &gt
100 ps, whereas the transients with the pump at other wavenumbers in this energy region show a single exponential decay with τ = 1-2 ps. We suggest that the τ1 represents the lifetimes of the 1nπ* energy levels near the D and E peaks, which are excited together by the ps pump pulse having a broad spectral bandwidth, and the τ2 shows the lifetimes of D and E peaks. The long lifetime of D level is attributed to a small barrier for internal conversion from the minimum of the 1L b state to the 1nπ* state. On the other hand, the long lifetime of E level is ascribed to the nuclear configuration of adenine at this level, which is unfavorable to reach the seam of the conical intersection leading to nearly barrierless deactivation to the electronic ground state. This study shows that the ps time-resolved spectroscopy provides a powerful tool to study mode- and energy-specific deactivation processes occurring in a multi-dimensional potential energy surface. © 2013 AIP Publishing LLC.

DOI： 10.1063/1.4821830

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Electronic and vibrational spectra of acetaminophen were measured by using UV-UV hole burning (HB) and IR dip spectroscopy. HB spectra show the coexistence of 4 different species, which include two new ones. Low-frequency transitions in the spectra are reproduced by a one-dimensional periodic potential with a free-rotor basis set for the methyl group. From the analysis, we concluded that acetaminophen has two conformers and each conformer gives two independent transitions starting from the most stable 0a(1) and the hot 1e internal rotational levels. It is also found that the HB spectrum of the trans-conformer in the previous report is that from the 1e excited level, while the HB spectrum of the cis-conformer is contaminated by the transitions of the trans-conformer. Potential curves of the methyl rotational motion are determined both in S-0 and S-1.

DOI： 10.1039/c2cp43552g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Rearrangement of intermolecular hydrogen bond in a monohydrated tryptamine cation, [TRA(H2O)(1)](+), has been investigated in the gas phase by IR spectroscopy and quantum chemical calculations. In the S-0 state of TRA(H2O)(1), a water molecule is hydrogen-bonded to the N atom of the amino group of a flexible ethylamine side chain [T. S. Zwier, J. Phys. Chem. A 105, 8827 (2001)]. A remarkable change in the hydrogenbonding motif of [TRA(H2O)](+) occurs upon photoionization. In the D-0 state of [TRA(H2O)(1)](+), the water molecule is hydrogen-bonded to the NH group of the indole ring of TRA(+), indicating that the water molecule transfers from the amino group to NH group. Quantum chemical calculations are performed to investigate the pathway of the water transfer. Two potential energy barriers emerge in [TRA(H2O)(1)](+) along the intrinsic reaction coordinate of the water transfer. The water transfer event observed in [TRA(H2O)(1)](+) is not an elementary but a complex process. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769878]

DOI： 10.1063/1.4769878

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

We present the resonance-enhanced multiphoton ionization, infrared-ultraviolet hole burning (IR-UV HB), and IR dip spectra of the trans-acetanilidemethanol (AAMeOH) cluster in the S0, S1, and cationic ground state (D0) in a supersonic jet. The IR-UV HB spectra demonstrate the co-existence of two isomers in S0,1, in which MeOH binds either to the NH or the CO site of the peptide linkage in AA, denoted as AA(NH)MeOH and AA(CO)MeOH. When AA(CO)MeOH is selectively ionized, its IR spectrum in D0 is the same as that measured for AA+(NH)MeOH. Thus, photoionization of AA(CO)MeOH induces migration of MeOH from the CO to the NH site with 100% yield.

DOI： 10.1002/cphc.201200704

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Photoactive proteins with cognate chromophores are widespread in organisms, and function as light-energy converters or receptors for light-signal transduction. Rhodopsins, which have retinal (vitamin A aldehyde) as their chromophore within their seven transmembrane alpha-helices, are classified into two groups, microbial (type-1) and animal (type-2) rhodopsins. In general, light absorption by type-1 or type-2 rhodopsins triggers a trans-cis or cis-trans isomerization of the retinal, respectively, initiating their photochemical reactions. Recently, we found a new microbial rhodopsin (middle rhodopsin, MR), binding three types of retinal isomers in its original state: all-trans, 13-cis, and 11-cis. Here, we identified the absolute absorption spectra of MR by a combination of high performance liquid chromatography (HPLC) and UV-vis spectroscopy under varying light conditions. The absorption maxima of MR with all-trans, 13-cis, or 11-cis retinal are located at 485, 479, and 495 nm, respectively. Their photocycles were analyzed by time-resolved laser spectroscopy using various laser wavelengths. In conclusion, we propose that the photocycles of MR are MR(trans) -&gt; MRK:lifetime = 93 mu s -&gt; MRM:lifetime = 12 ms -&gt; MR, MR(13-cis) -&gt; MRO-like:lifetime = 5.1 ms -&gt; MR, and MR(11-cis) -&gt; MRK-like:lifetime = 8.2 mu s -&gt; MR, respectively. Thus, we demonstrate that a single photoactive protein drives three independent photochemical reactions.

DOI： 10.1021/jp302357m

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Three-residue peptides capped with benzyloxycarbonyl (Z-) group, Z-Pro-Leu-Gly-NH2 and Z-Pro-Leu-Gly-OH, are investigated by infrared (IR) spectroscopy, using supersonic-jet laser desorption technique, in the N-H and O-H stretching frequency ranges. The IR spectra show clear evidence of the formation of different hydrogen-bonding network in the two peptides. The possible gas phase structure is proposed from density functional theory calculations using cc-pVDZ basis set. The Z-Pro-Leu-Gly-OH in the gas phase forms successive gamma-turn structure with free C-terminal carboxyl group whereas main structural element in Z-Pro-Leu-Gly-NH2 is beta-turn with C-terminal -NH2 group forming hydrogen bond. Structural information is employed to predict their binding capability in gas phase. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2012.01.086

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We describe here the key technical elements of a two-color tunable IR/VUV photoionization TOF mass spectrometer system which allows a wide-range of high-resolution experiments to be performed on a diverse range of cold molecules and clusters in a molecular beam. In particular we highlight the methods we have applied to provide efficient wavelength separation of the VUV radiation from the longer wavelength components used to generate it and discuss a number of systems that we have studied with the instrument which highlight its flexibility for use in the study of molecular spectroscopy. (C) 2012 American Institute of Physics. [doi:10.1063/1.3673639]

DOI： 10.1063/1.3673639

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

A method for the source apportionment of individual particles was developed by using high lateral resolution time-of-flight secondary ion mass spectrometry (TOF-SIMS). The procedure of this method was optimized through the analysis of some kind of pure metal particles. This method was applied to the aerosol particles collected for a week at Fukue-Island in Japan. As the results, the aerosol particles on characteristic days were classified into 10 clusters with different sources. The variation of pollution aerosols was consistent with that deduced by the bulk chemical analysis. We concluded that the developed method was effective to the source apportionment of suspended particulate matters.

DOI： 10.3131/jvsj2.55.104

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201203296

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The ionisation-induced pi -&gt; H site switching reaction in clusters of phenol solvated by rare gas ligands, PhOH-Rg(n) (Rg = Ar and Kr, n = 1-3), is characterised by electron impact infrared (EI-IR) photodissociation as well as nanosecond and picosecond time-resolved UV-UV-IR spectroscopy. The EI-IR spectra of the PhOH+-Rg dimers demonstrate that the H-bound isomer is the most stable structure in the ground electronic state of the cation, in which the Rg atom forms a hydrogen bond to the OH group of PhOH+. The pi-bound structure, in which the Rg ligand is attached to the aromatic ring, is also weakly detected as a less stable structure in the EI-IR spectrum. The IR spectra of the PhOH+-Rg dimers change drastically, when the cluster cations are generated by resonance-enhanced multiphoton ionisation (REMPI). The metastable pi-bound structure becomes the major species and dominates the population. The picosecond time-resolved REMPI-IR spectra clearly demonstrate the initial population of the pi-bound structure by ionisation, the subsequent pi -&gt; H site switching to the H-bound site, and the eventual formation of an pi -&gt; H equilibrium population by the H -&gt; pi back reaction. Classically, this intermolecular pi &lt;-&gt; H structural rearrangment corresponds to a pendular motion of Rg atom around PhOH+. The pi -&gt; H switching dynamics is sensitively affected by the addition of one or more Rg ligands with respect to the reaction mechanism and the rate constants. In larger PhOH+-Rg(n) clusters (n &gt;= 2), the initially populated pi-bound structure is completely converted into the H-bound structure by a one-way single-step reaction with a single exponential decay on the picosecond timescale. This principal change in the reaction mechanism is rationalised by efficient intermolecular vibrational energy redistribution from the reaction coordinate to modes of the available spectator ligand(s), which completely quenches the H -&gt; pi back reaction for n &gt;= 2. Structures, energetics and dynamics of this pi-H site switching, along with a quantum chemical description based on wavepacket dynamics are discussed. Significantly, these spectroscopic experiments for PhOH+-Rg(n) represent the first time-resolved studies of intermolecular rearrangment reactions in molecular clusters.

DOI： 10.1080/0144235X.2012.656013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Infrared spectra of protected amino acids, N-benzoxycarbonyl-L-proline and N-benzoxycarbonyl-L-isoleucine were measured in the gas phase from 10 to 3 mu m. 4 and 3 conformers were found, respectively. The spectra in the 3 mu m region reveal the carboxylic OH and amide NH bonds do not participate in hydrogen bonding with neighboring amide groups despite the highest acidity in the molecule. The spectra ill the 10-5 mu m region imply the main chain structure is the same among the conformers.

DOI： 10.1246/cl.2011.1157

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In our previous work, we found that synephrine has six conformers in the gas phase, while adrenaline, which is a catecholamine and has the same side chain as synephrine, has been reported to have only two conformers. To determine the conformational geometries of synephrine, we measured resonance enhanced multiphoton ionization, ultraviolet ultraviolet hole burning, and infrared dip spectra by utilizing the laser desorption supersonic jet technique. By comparing the observed infrared spectra with theoretical ones, we assigned geometries except for the orientations of the phenolic OH group. Comparison between the determined structures of synephrine and those of 2-methylaminno-1-phenylethanol, which has the same side chain as synephrine but no phenol OH group, leads to the conclusion that the phenolic OH group in synephrine does not affect the conformational flexibility of the side chain. In the case of adrenaline, which is expected to have 12 conformers if there are no interactions between the catecholic OH groups and the side chain, some interactions possibly exist between them because only two conformations are observed. By estimation of the dipole dipole interaction energy between partial dipole moments of the catecholic OH groups and the side chain, it was concluded that the dipole dipole interaction stabilizes specific conformers which are actually observed.

DOI： 10.1021/jp205267c

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Infrared (IR) spectra of phenol-Ar/Kr in high-n Rydberg states converging to the cation ground state were measured by autoionization detected IR (ADIR) spectroscopy. Although the clusters were excited via the S-1 state of the pi-bound structures, the ADIR spectra exhibit free and hydrogen-bonded OH stretching vibrations (V-OH). Thus, similar to direct photoionization, excitation into high-n Rydberg states causes the pi-H site switching of the rare gas ligand from the aromatic ring to the OH group. This result demonstrates that the Rydberg electron is insensitive to the dynamics in the ion core. (C) 2011 Published by Elsevier B.V.

DOI： 10.1016/j.cplett.2011.08.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Hole-burning spectra of m-fluorophenol/ammonia (1:3) clusters are measured by four-color UV-near IR-UV-UV hole-burning spectroscopy. Cis and trans isomers of the cluster are clearly distinguished in the (1:3) cluster. Picosecond time evolutions of the excited state hydrogen transfer (ESHT) reaction in the (1:3) clusters are measured by the ion depletion due to 3p-3s Rydberg transition of reaction products center dot NH4(NH3)(2) lying in the near infrared region. From the wavelength dependence of the time evolution, we have concluded 1) the initial formation of a metastable center dot NH4-NH3-NH3 radical and 2) successive isomerization to the most stable NH3-center dot NH4-NH3 radical in both cis and trans isomers. The reaction lifetimes of ESHT are determined by the rate equation analysis as 32.4 and 31.8 ps for the cis and trans isomer, respectively, and the isomerization and its back-reaction lifetime of both isomers are determined to be 3.3 ps and 11.2 ps. The almost same reaction rates are consistent with the similarity of the hydrogen bond networks in both clusters.

DOI： 10.1002/cphc.201100102

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Language：Japanese  

CiNii Books

J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The conformational reduction in catecholamine neurotransmitters was studied by resonance enhanced multi photon ionization (REMPI), ultraviolet-ultraviolet (UV-UV) hole burning and infrared (IR) dip spectroscopy with applying a laser desorption supersonic jet technique to DOPA, which is one of the catecholamine neurotransmitters and has one more phenolic OH group than tyrosine. It is concluded that DOPA has a single observable conformer in the gas phase at low temperature. Quantum chemical calculations at several levels with or without the dispersion correction were also carried out to study stable conformations. From the comparison between the computational IR spectra and the experimental ones, the most stable structure was determined. It is strongly suggested that the conformational reduction is caused by electrostatic interactions, such as a dipole-dipole interaction, between the chain and OH groups.

DOI： 10.1039/c0cp02695f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN  

The film patterned by the resin Black Matrix (BM) photoresist, which has two features, the lower reflectivity and low stress on environment of a processing developer than the chromium oxide (CrO) photoresist, is applied to the color filter (CF) in the Liquid Crystal Display (LCD). However, the new panel technology, that is required more lower environmental impact, needs lower reflectivity and narrower negative-tone pattern for the resin BM resist in recent years. We investigated the lower reflectivity resin BM resist film with the mill base comprised of the pigment alloyed silver and tin. The thermo gravimetric analysis (TGA) indicated a significant difference on a surface roughness (Ra) measured on an atomic forced microscope (AFM). Moreover, we observed a contact angle of 2-methoxy-1-methyl acetate (PGMEA) on the film with fluorin-cotaning polymer after post-bake at 220 degrees C. From these results, we concluded that the resin BM resist film comprised of the Ag-Sn mill base make lower reflective and narrower negative-tone pattern.

DOI： 10.2494/photopolymer.24.397

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN  

Negative photopolymerizing photoresists can be cured in a short time, as compared to thermosetting photoresists, and have advantages in reducing the energy, cost and volatile organic compound (VOC) generated therefore. They are utilized as a curing system for large-size liquid crystal panels, of which sizes are lengths more than 2 m. Therefore, novel photo polymerization initiators, which generate radicals more efficiently, have been investigated. However, compounds which substitute phenyl group in the oxime end have promptly occurred to E/Z-isomerization around C=N bonds. This isomerization remarkably decreases quantum yield of radical production in N-O bond cleavage. The authors investigate the influence to photolithography by the isomeric structure of O-acyloxime ester compounds and the selective synthetic process of isomeric structure. Consequently, a selective isomer synthesis method for E and Z isomers has been established by controlling the reaction temperature. Furthermore, evaluations of the pattern formation using these isomers areperformed. The evaluations have revealed that patterns are formed by using the E isomer with lower energy than that required by using the Z isomer.

DOI： 10.2494/photopolymer.24.625

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Electronic excitation spectra of the S-1 &lt;- S-0 transition obtained by resonance-enhanced two-photon ionization (REMPI) are analysed for phenol-Ar-n (PhOH-Ar-n) clusters with n &lt;= 4. An additivity rule has been established for the S-1 origin shifts upon sequential complexation at various pi binding sites, which has allowed for the identification of two less stable isomers not recognized previously, namely the (2/0) isomer for n = 2 and the (2/1) isomer for n = 3. Infrared (IR) spectra of neutral PhOH-Ar-n and cationic PhOH+-Ar-n clusters are recorded in the vicinity of the OH and CH stretch fundamentals (nu(OH), nu(CH)) in their S-0 and D-0 ground electronic states using IR ion dip spectroscopy. The small monotonic spectral redshifts Delta nu(OH) of about -1 cm(-1) per Ar atom observed for neutral PhOH-Ar-n are consistent with p-bonded ligands. In contrast, the IR spectra of the PhOH+-Ar-n cations generated by resonant photoionization of the neutral precursor display the signature of pi-bonded isomers, suggesting that ionization triggers an isomerization reaction, in which one of the p-bonded Ar ligands moves to the more attractive OH site. The dynamics of this isomerization reaction is probed for PhOH+-Ar-3 by picosecond time-resolved IR spectroscopy. Ionization of the (3/0) isomer of PhOH+-Ar-3(3 pi) with three pi-bonded Ar ligands on the same side of the aromatic ring induces a pi -&gt; H switching reaction toward the PhOH+-Ar-3(H/2 pi) isomer with a time constant faster than 3 ps. Fast intracluster vibrational energy redistribution prevents any H -&gt; pi back reaction.

DOI： 10.1039/c0cp01926g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The dynamics of the intermolecular motion of the phenol(+)-Kr cation generated by photoionization of the neutral p-structure is probed by picosecond time-resolved infrared spectroscopy. The spectrum at zero delay displays only the free OH stretch band of the pi-structure. The appearance of the hydrogen-bonded OH stretch band of the H-structure after a few ps is due to ionization-induced pi -&gt; H site switching. Spectra at long delay (&gt;20 ns) show that the Kr atom delocalizes from one pi-site of the aromatic ring to the opposite pi-site via the OH-site, like a pendular motion in the classical picture.

DOI： 10.1039/c0cp01961e

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Language：English   Publisher：The Biophysical Society of Japan General Incorporated Association  

DOI： 10.2142/biophys.51.S100_1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

Exhaust emissions from a diesel vehicle were studied using FTIR, SMCA-REMPI, and SMPS. With these techniques, quantitative emission properties of NO, NO2, N2O, NH3, CO, CH4, C2H4, C3H6, HCHO, toluene, toluene + CH2, toluene + 2CH(2), beta-methylstyrene, naphthalene, 2-methylnaphthalene, phenanthrene, and o-cresol, as well as particle size distributions, were obtained in constant-speed operation at 0-80 km/h, which corresponds to a brake mean effective pressure (BMEP) of 0-293 kPa. NO emission increased as the in-cylinder temperature increased, corresponding to increased engine load. NO2 and N2O had a strong correlation to equivalence ratio. The emission characteristics of non-aromatic hydrocarbons depended on engine load. At low load, the emissions were high because low in-cylinder temperature and Exhaust Gas Recycling (EGR) prevented complete fuel oxidation. Equivalence ratio had a slight influence on the non-aromatic hydrocarbon emissions. The profiles of aromatic hydrocarbon exhibited two shapes. One was a toluene group and another was a styrene and naphthalene group. The shapes of the toluene group were similar to those of non-aromatic hydrocarbons. On the other hand, the styrene and naphthalene group emissions at idling were low, suggesting that they were not formed at low load. These features concerning the two groups of aromatic hydrocarbons were also observed in a transient driving cycle. Emission of accumulation mode particles was correlated with equivalence ratio. Higher emissions were observed when the equivalence ratio was higher, and the particle diameters also increased. Emission of nucleation mode particles increased as the engine load increased, because the amount of injected fuel per cycle increased. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

DOI： 10.1016/j.proci.2010.07.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The 4-fluorotoluene-ammonia van der Waals complex has been studied using IR-UV depletion and hole-burning spectroscopies with assignments supported by ab initio and DFT calculations of ground state binding energies and intramolecular vibrational frequencies. The experimental IR-UV depletion and hole-burning spectra presented here provide unequivocal empirical evidence that the 4FT-NH3 complex exists in two almost equally stable conformational forms. Both isomers contribute intensity to the experimental R2PI spectrum with one responsible for bands appearing to the red of the 4FT band origin position, and the other for those appearing immediately to the blue. On the basis of comparison of computed NH stretching frequencies with those obtained from the IR-UV spectra, the red-shifted bands are assigned to a pi-proton-acceptor complex featuring an NH center dot center dot center dot pi-hydrogen bond, and the blue-shifted bands are assigned to an in-plane sigma-complex in which the ammonia binds in the plane of the ring forming a double-hydrogen-bonded six-membered ring with the fluorine atom. Ground state interaction energies computed at the M06-2X/cc-pVTZ level were found to compare favourably with those obtained at the CCSD(T) CBS level, although the former resulted in overbinding of the pi-complex compared with the in-plane conformer, a characteristic shared with MP2 level calculations. The observation of a pi-complex in addition to a sigma-complex is consistent with the conclusion that the electron-donating power of the methyl group is sufficiently large to counter-balance the electron-withdrawing power of the fluorine atom.

DOI： 10.1039/c1cp21545k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The phenol(+)center dot center dot center dot Ar-2 complex has been characterized in a supersonic jet by mass analyzed threshold ionization (MATI) spectroscopy via different intermediate intermolecular vibrational states of the first electronically excited state (S-1). From the spectra recorded via the S(1)0(0) origin and the S-1 beta(x) intermolecular vibrational state, the ionization energy (IE) has been determined as 68 288 +/- 5 cm(-1), displaying a red shift of 340 cm(-1) from the IE of the phenol(+) monomer. Well-resolved, nearly harmonic vibrational progressions with a fundamental frequency of 10 cm(-1) have been observed in the ion ground state (D-0) and assigned to the symmetric van der Waals (vdW) bending mode, beta(x), along the x axis containing the C-O bond. MATI spectra recorded via the S-1 state involving other higher-lying intermolecular vibrational states (sigma(1)(s), beta(3)(x), sigma(1)(s)beta(1)(x), sigma(1)(s)beta(2)(x)) are characterized by unresolved broad structures.

DOI： 10.1039/c004497k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The structures, binding energies, and vibrational and electronic spectra of various isomers of neutral and ionic phenol-Ar-n clusters with n &lt;= 4, PhOH(+)-Ar-n, are characterized by quantum chemical calculations. The properties in the neutral and ionic ground electronic states (S-0, D-0) are determined at the M06-2X/aug-cc-pVTZ level, whereas the S-1 excited state of the neutral species is investigated at the CC2/aug-cc-pVDZ level. The Ar complexation shifts calculated for the S-1 origin and the adiabatic ionisation potential, Delta S-1 and Delta IP, sensitively depend on the Ar positions and thus the sequence of filling the first Ar solvation shell. The calculated shifts confirm empirical additivity rules for Delta S-1 established recently from experimental spectra and enable thus a firm assignment of various S-1 origins to their respective isomers. A similar additivity model is newly developed for Delta IP using the M06-2X data. The isomer assignment is further confirmed by Franck-Condon simulations of the intermolecular vibrational structure of the S-1 &lt;- S-0 transitions. In neutral PhOH-Ar-n, dispersion dominates the attraction and pi-bonding is more stable than H-bonding. The solvation sequence of the most stable isomers is derived as (10), (11), (30), and (31) for n &lt;= 4, where (km) denotes isomers with k and m Ar ligands binding above and below the aromatic plane, respectively. The pi interaction is somewhat stronger in the S-1 state due to enhanced dispersion forces. Similarly, the H-bond strength increases in S-1 due to the enhanced acidity of the OH proton. In the PhOH+-Ar-n cations, H-bonds are significantly stronger than pi-bonds due to additional induction forces. Consequently, one favourable solvation sequence is derived as (H00), (H10), (H20), and (H30) for n &lt;= 4, where (Hkm) denotes isomers with one H-bound ligand and k and m pi-bonded Ar ligands above and below the aromatic plane, respectively. Another low-energy solvation motif for n - 2 is denoted (11)(H) and involves nonlinear bifurcated H-bonding to both equivalent Ar atoms in a C-2v structure in which the OH group points toward the midpoint of an Ar-2 dimer in a T-shaped fashion. This dimer core can also be further solvated by pi-bonded ligands leading to the solvation sequence (H00), (11)(H), (21)(H), and (22) for n &lt;= 4. The implications of the ionisation-induced pi -&gt; H switch in the preferred interaction motif on the isomerisation and fragmentation processes of PhOH(+)-Ar-n are discussed in the light of the new structural and energetic cluster parameters.

DOI： 10.1039/c1cp20676a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp106204d

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The dissociation energetics in the phenol(+)center dot center dot center dot Ar-2(2 pi) cluster ion have been investigated using photoionization efficiency and mass analyzed threshold ionization spectroscopy. The appearance energies for the loss of one and two Ar atoms are determined as similar to 210 and similar to 1115 cm(-1), respectively. The difference between the appearance energy for the first Ar ligand in phenol(+)center dot center dot center dot Ar-2(2 pi) and the dissociation energy of the phenol(+)center dot center dot center dot Ar(pi) dimer (535 cm(-1)) is explained by the isomerization of one pi-bound Ar ligand to the OH binding site (H-bond) upon ionization. The energy difference between phenol(+)center dot center dot center dot Ar-2(2 pi) and phenol(+)center dot center dot center dot Ar2(H/pi) could also be estimated to be around 325 cm(-1), which corresponds roughly to the difference of the binding energy of a pi-bound and H-bound Ar ligands. The binding energy of the H-bound Ar atom in phenol(+)center dot center dot center dot Ar-2(H/pi) is derived to be similar to 905 cm(-1). (C) 2010 American Institute of Physics. [doi:10.1063/1.3482733]

DOI： 10.1063/1.3482733

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The various dissociation thresholds of phenol(+)center dot center dot center dot Ar-3 complexes for the consecutive loss of all three Ar ligands were measured in a molecular beam using resonant photoionization efficiency and mass analyzed threshold ionization spectroscopy via excitation of the first excited singlet state (S-1). The adiabatic ionization energy is derived as 68077 +/- 15 cm(-1). The analysis of the dissociation thresholds demonstrate that all three Ar ligands in the neutral phenol center dot center dot center dot Ar-3 tetramer are attached to the aromatic ring via pi-bonding, denoted phenol center dot center dot center dot Ar-3(3 pi). The value of the dissociation threshold for the loss of one Ar ligand from phenol(+)center dot center dot center dot Ar-3(3 pi), similar to 190 cm(-1), is significantly lower than the binding energy measured for the pi-bonded Ar ligand in the phenol(+)center dot center dot center dot Ar(pi) dimer, D-0 = 535 +/- 3 cm(-1). This difference is rationalized by an ionization-induced pi -&gt; H isomerization process occurring prior to dissociation, that is, one Ar atom in phenol+center dot center dot center dot Ar-3(3 pi) moves to the OH binding site, leading to a structure with one H-bonded and 2 pi-bonded ligands, denoted phenol(+)center dot center dot center dot Ar-3(H/2 pi). The dissociation thresholds for the loss of two and three Ar atoms are also reported as 860 and 1730 cm(-1). From these values, the binding energy of the H-bound Ar atom can be estimated as 870 cm(-1).

DOI： 10.1021/jp102491b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have investigated the excited-state multiple-proton/hydrogen atom transfer reactions in the 7-azaindole water clusters, [7AI](H2O)(n) (n = 2,3), in the gas phase by combining electronic spectroscopy and quantum chemical calculations. The fluorescence excitation (FE) spectrum of 7AI(H2O)(2) has been observed by monitoring visible emission. In contrast, no vibronic bands are detected in the FE spectrum of 7AI(H2O)(3) when the visible emission is monitored. The dispersed fluorescence spectra of 7AI(H2O)(n) (n = 2,3) have been measured. The excitation of +180 cm(-1) band from the electronic origin of 7AI(H2O)(2) enhances the visible emission as compared with the 0-0 excitation. The +180 cm(-1) band is assgined to an intermolecular mode (sigma(1)) of the cyclic hydrogen-bonded ring structure. The calculated S-1-S-0 absorption spectrum for the cyclic hydrogen-bonded structure is in agreement with the FE spectrum around the 0-0 region. The excitation of sigma(1) significantly promotes the reaction and generates the tautomeric form of 7AI(H2O)(2). These experimental results on 7AI(H2O)(n) (n = 2,3) are very similar to those on 7AI(CH3OH)(n) (n = 2,3) and 7AI(C2H5OH)(n) (n = 2,3). We conclude that the excited-state triple proton/hydrogen atom transfer (ESTPT/HT) occurs in 7AI(H2O)(2). Cuts of the potential energy surfaces along the proton/hydrogen atom transfer coordinates of 7AI(H2O)(n) (n = 2,3) and 7AI(CH3OH)(n) (n = 2,3) are comparatively calculated by quantum chemistry calculations (RI-CC2/cc-pVDZ and TD-DFT(B3LYP)/cc-pVDZ) to explore the mechanism of the ESTPT/HT reaction. The calculated results suggest that concerted proton transfers occur in 7AI(H2O)(2) as well as in 7AI(CH3OH)(2), whereas the potential barrier for the excited-state quadruple proton transfer in 7AI(H2O)(3) and 7AI(CH3OH)(3) is higher than those for ESTPT. The theoretical results are consistent with the observation of ESTPT/HT in 7AI(H2O)(2).

DOI： 10.1021/jp102733c

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A large-size 1-naphthol cluster, (1-NpOH)(n), with n &lt;= 30 was prepared by using a high-pressure pulsed valve. The electronic and vibrational transitions of (1-NpOH)(n) with n = 3-9 were measured by resonant two-photon ionization (R2PI) and ion-detected IR dip spectroscopies. The S-1 &lt;- S-0 R2PI spectrum shows partially resolved structures around the origin band in the (1-NpOH)(n) cluster with n = 3-8. The (1-NpOH)(3) and the (1-NpOH)(6) clusters show relatively sharp origin bands. The structure of (1-NpOH)(3) was determined by comparison of the IR dip spectrum with the simulated one by DFT calculation, while those of (1-NpOH)(n) (n &gt;= 4) were discussed in terms of topological geometries of a hydrogen-bonded network. Those analyses suggest that (i) the (1-NpOH)(3) cluster has the cyclic structure where three 1-NpOH monomers are linked by both the hydrogen-bonding and the pi center dot center dot center dot C-H interaction between naphthyl rings and (ii) the (1-NpOH)(n) cluster with n &gt;= 4 is built up by attaching the 1-NpOH monomers to the (1-NpOH)(3) core.

DOI： 10.1021/jp102849q

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Lifetimes of the first electronic excited state (S(1)) of fluorine and methyl (o-, m-, and p-) substituted phenols and their complexes with one ammonia molecule have been measured for the 00 transition and for the intermolecular stretching sigma(1) levels in complexes using picosecond pump-probe spectroscopy. Excitation energies to the S(1) (pi pi*) and S(2) (pi sigma*) states are obtained by quantum chemical calculations at the MP2 and CC2 level using the aug-cc-pVDZ basis set for the ground-state and the S(1) optimized geometries. The observed lifetimes and the energy gaps between the (pi pi*) and (pi sigma*) states show a good correlation, the lifetime being shorter for a smaller energy gap. This propensity suggests that the major dynamics in the excited state concerns an excited state hydrogen detachment or transfer (ESHD/T) promoted directly by a S(1)/S(2) conical intersection, rather than via internal conversion to the ground-state. A specific shortening of lifetime is found in the o- fluorophenol-ammonia complex and explained in terms of the vibronic coupling between the pi pi* and pi sigma* states occurring through the out-of-plane distortion of the C-F bond. (C) 2010 American Institute of Physics. [doi:10.1063/1.3480396]

DOI： 10.1063/1.3480396

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Language：Japanese  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We developed a new convertible copper(I) complex using 2-pyridyl-4-methylpyrimidine and diphosphine as ligands. This complex exhibited mechanical bistability based on the inversion motion of the pyrimidine ring, leading to dual luminescence behavior. The inversion dynamics was strongly dependent on temperature and solvent. Variable-temperature H-1 NMR spectra revealed that the two isomers interconverted in solution via ring inversion, and the motion was frozen below 200 K. The complex exhibited characteristic CT absorption and emission bands in solution. Emission lifetime measurements demonstrated that the emission could be deconvoluted into two components. The fast and slow components were assigned to the two isomers, the excited states of which were characterized by different structural relaxation process and/or additional solvent coordination properties. The emission properties of the two isomers differed not only in lifetime and wavelength but also in heat sensitivity. The molar ratio of the two isomers varied with the polarity of the solvent via electrostatic interactions with the counteranion. The rate of inversion was affected by solvent, suggesting that inversion was promoted by solvent coordination.

DOI： 10.1021/ja103718e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

We performed infrared (IR) spectroscopic imaging of molecular species in cultured cell interiors of A549 cells using in-house developed vibrational sum-frequency generation detected IR super-resolution microscope. The spatial resolution of this IR microscope was approximately 1.1 mu m, which exceeds the diffraction limit of IR light. Therefore, we clearly observed differences in the signal intensity at various IR wavelengths which appear to originate from the differing IR absorptions of specific vibrational modes, and reveal the distribution of molecular species in the single cell. These results were never imaged with the conventional IR microscope. (C) 2010 Optical Society of America

DOI： 10.1364/OE.18.013402

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In the neurotransmission process, a specific neurotransmitter binds to a specific receptor in a "key and lock" recognition process. Neurotransmitters, such as the catecholamines, are flexible molecules that can change their shape easily in principle. However, conformations of both the "key" and "lock" must be quite limited to achieve high selectivity. We have investigated the conformational diversity of catecholamines and related molecules by laser spectroscopy. Molecules of the tyrosine family, which contain a phenolic aromatic chromophore, exist as several conformers. In contrast, a single conformer is observed in dopa and other catecholamines, which contain two hydroxyl groups on the benzene moiety (catechol). This demonstrates that the presence of a catechol ring restricts significantly the number of stable conformations.

DOI： 10.1021/jz100186h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC APPLIED SPECTROSCOPY  

We report single-cell infrared (IR) imaging of onion (Allium cepa) root cells using an IR super-resolution microscope based on vibrational sum-frequency generation (VSFG). The resolution of recorded IR images was less than 2 mu m and IR super-resolution was achieved by virtue of the VSFG detection. In addition, IR spectra measurements were successfully performed on distinct intra-cellular assemblies. The IR absorption intensity of the cell nuclear edge and the nucleolus in the 3055-3130 cm I region was stronger than that from the cytoplasmic part. This is because the cell nucleus and nucleolus contain larger amounts of nucleic acid. Thus, the obtained IR spectra reflect differences in chemical composition among different cellular structures. In addition, the ability of our novel IR super-resolution microscope to obtain distinct information on both VSFG and two-photon fluorescence is demonstrated.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A scanning visible-super-resolution microscope based on the saturation behaviour of transient fluorescence detected infrared (TFD-IR) spectroscopy is proposed. A Gaussian IR beam, a Gaussian visible beam and a Laguerre-Gaussian (LG) visible beam are Used to obtain two separate two-color excitation fluorescence (2CF) images of the sample. The final image is obtained as the difference between the two recorded images. If the peak intensity of the LG beam is high enough to induce saturation in the fluorescence signal, the image can, in principle, have unlimited spatial resolution. A similar to 3-fold improvement in transverse resolution over the visible diffraction limit (and far exceeding the IR diffraction limit) is easily achievable in present experimental setups. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2009.10.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Sensory rhodopsin 1 (SRI) functions as a dual receptor regulating both negative and positive phototaxis. It transmits light signals through changes in protein-protein interactions with its transducer protein, HtrI. The phototaxis function of Halobacterium salinarum SRI (HsSRI) has been well characterized using genetic and molecular techniques, whereas that of Salinibacter ruber SRI (SrSRI) has not. SrSRI has the advantage of high protein stability compared with HsSRI and, therefore, provided new Information about structural changes and Cl(-) binding of SRI. However, nothing is known about the functional role of SrSRI in phototaxis behavior. In this study, we expressed a SRI homologue from the archaeon Haloarcula vallismortis (Hi,SRI) as a recombinant protein which uses all-trans-retinal as a chromophore. Functionally important residues of HsSRI are completely conserved in Hi,SRI (unlike in SrSRI), and Hi,SRI is extremely stable in buffers without Cl(-). Taking advantage of the high stability, we characterized the photochemical properties of Hi,SRI under acidic and basic conditions and observed the effects of Cl- oil the protein under both conditions. Fourier transform infrared results revealed that the structural changes in HvSRI were quite similar to those in HsSRI and SrSRI. Thus, HvSRI can become a useful protein model for improving Our understanding of the molecular mechanism of the dual photosensing by SRI.

DOI： 10.1021/bi901824a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

DOI： 10.1016/j.jmb.2009.10.046

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Direct photoionization of supersonic jet-cooled n-propylbenzene and m-fluorophenol was observed using a tunable VUV laser fitted with a custom-made 4-prism wavelength separator. Distinct ionization thresholds were readily measured for the two stable rotational isomers in each case, and the adiabatic ionization energies were determined to be 70 410 cm(-1) and 70 269 cm(-1) for the gauche and trans forms of n-propylbenzene and 70 193 cm(-1) and 70 451 cm(-1) for the cis and trans isomers of m-fluorophenol, respectively. These values are in excellent agreement with literature values determined from two-color (1 + 1&apos;) REMPI experiments and demonstrate the utility of the tunable VUV system in the study of photoionization processes in molecular beam experiments. (C) 2009 Published by Elsevier B. V.

DOI： 10.1016/j.cplett.2009.12.023

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A simultaneous multi-composition analyzing (SMCA) resonance enhanced multi-photon ionization (REMPI) system was used to investigate gasoline engine exhaust. Observed peaks for exhaust were smaller mass numbers than those from diesel exhaust. However, large species up to three ring aromatics were observed suggesting that soot precursor forms even in the gasoline engine. At low catalyst temperature condition, the reduction efficiencies of a three-way catalyst were higher for higher mass numbers. This result indicates that the larger species accumulate in the catalyst or elsewhere due to their lower vapor pressures. To evaluate the emission of low volatility species, the accumulation should be taken into account. In the hot mode, reduction efficiencies for aromatic species of three-way catalyst were almost 99.5% however, they fall to 70% in the cold start condition. © 2009 SAE International.

DOI： 10.4271/2009-01-2742

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS LTD  

Time-resolved measurements of the concentration of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in exhaust from a diesel vehicle fitted with an oxidation catalyst and operated in JE05 mode are performed at a sensitivity of 10ppb using a supersonic jet/resonance enhanced multi-photon ionization (jet-REMPI) method. The concentrations of benzene, naphthalene, and phenol in exhaust from the test vehicle are measured before entering and after exiting from the oxidation catalyst. The total hydrocarbon (THC) is measured simultaneously using a constant volume sample (CVS) instrument fitted with a flame ionization detector (FID). Concentration changes of benzene, naphthalene and phenol are recorded at 1 s intervals and quantified using standard samples. Comparison of these signals with the real-time THC data shows that the time dependence of the individual species is almost the same as that of the THC before the oxidation catalyst but substantially different after.

DOI： 10.1243/14680874JER03909

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Language：English   Publishing type：Part of collection (book)   Publisher：John Wiley and Sons  

DOI： 10.1002/9783527627820.ch29

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Language：Japanese   Publisher：The Laser Society of Japan  

DOI： 10.2184/lsj.37.728

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Sensory rhodopsin I (SRI) exists in the cell membranes of microorganisms such as the archaeon Halobacterium salinarum and is a photosensor responsible for positive and negative phototaxis. SRI forms a signaling complex with its cognate transducer protei HtrI, in the membrane. That complex transmits light signals to the flagellar motor through changes in protein-protein interactions with the kinase CheA and the adaptor protein CheW, which controls the direction of the rotation of the flagellar motor. Recently, we cloned and characterized Salinibacter sensory rhodopsin I (SrSRI), which is the first SRI-like protein identified in eubacteria [Kitajima-Ihara, T., et al. (2008) J. Biol. Chem. 283, 23533-23541]. Here we cloned and expressed SrSRI with its full-length transducer protein, SrHtrI, as a fusion construct. We succeeded in producing the complex in Escherichia coli as a recombinant protein with high quality having all-trans-retinal as a chromophore for SRI, although the expression level was low (0.10 mg/L of culture). In addition, we report here the photochemical properties of the SrSRI-SrHtrI complex using time-resolved laser flash spectroscopy and other spectroscopic techniques and compare them to SrSRI without SrHtrI.

DOI： 10.1021/bi901338d

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

Microbial organisms utilize light not only as energy sources but also as signals by which rhodopsins (containing retinal as a chromophore) work as photoreceptors. Sensory rhodopsin I (SRI) is a dual photoreceptor that regulates both negative and positive phototaxis in microbial organisms, such as the archaeon Halobacterium salinarum and the eubacterium Salinibacter ruber. These organisms live in highly halophilic environments, suggesting the possibility of the effects of salts on the function of SRI. However, such effects remain unclear because SRI proteins from H. salinarum (HsSRI) are unstable in dilute salt solutions. Recently, we characterized a new SRI protein (SrSRI) that is stable even in the absence of salts, thus allowing us to investigate the effects of salts on the photochemical properties of SRI. In this study, we report that the absorption maximum of SrSRI is shifted from 542 to 556 nm in a Cl(-)-dependent manner with a K(m) of 307 +/- 56 mM, showing that Cl(-)-binding sites exist in SRI. The bathochromic shift was caused not only by NaCl but also by other salts (NaI, NaBr, and NaNO(3)) implying that I(-), Br(-), and NO(3)(-) can also bind to SrSRI. In addition, the photochemical properties during the photocycle are also affected by chloride ion binding. Mutagenesis studies strongly suggested that a conserved residue, His131, is involved in the Cl(-)-binding site. In light of these results, we discuss the effects of the Cl(-) binding to SRI and the roles of Cl(-) binding in its function. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jmb.2009.06.050

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

IR absorption of chemical species in microscopic objects such as biological cells cannot be measured by conventional IR microscopes, because of their low resolution. To overcome this problem, we developed a novel far-field IR super-resolution microscope employing transient fluorescence detected IR spectroscopy. The resolution of this microscope was shown to be 880 nm by measuring the image of 1 mu m fluorescent beads. Furthermore, it succeeded in resolving beads located 1.4 mu m apart from each other. This is considerably smaller than the diffraction limit of the applied IR light (3.4 mu m). These results suggest the capability of our microscope to study sub-micron targets such as sub-cellular structures of biological cells. (C) 2009 Optical Society of America

DOI： 10.1364/OE.17.012013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Resorcinol(+)-Ar-n cations (Rs(+)-Ar-n, n = 1,2) generated by resonant multiphoton ionization (REMPI) and electron ionization (EI) were assayed by their infrared (IR) photodissociation spectra in the OH stretch (nu(OH)) range. Several isomers distinguished by their Ar ligand binding sites and their Rs(+) isomeric cores are identified by characteristic Lambda nu(OH) complexation shifts. Neutral Rs-Ar-n complexes prefer intermolecular pi-bonding of Ar to the aromatic ring, whereas cationic Rs(+)-Ar-n clusters show predominant H-bonding to the acidic OH groups. The REMPI-IR spectra of Rs(+)-Ar-2 reveal mOH absorptions assigned to cold pi-bound complexes and hot H-bound complexes. The latter are generated via ionization-induced intermolecular pi -&gt; H isomerization. (C) 2009 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.cplett.2009.04.030

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Laser Surgery and Medicine  

2-color infrared (IR) super-resolution microscopy enables us to detect IR absorption with resolution of less than 1 μm, which is equivalent to that of fluorescence microscope. To prove that this microscopy can be utilized as cell analysis, we attempted to detect IR absorption inside A549 cells at IR wavelength of about 3 μm. When stained, we achieved to detect the IR absorption of protein molecules bound to fluorescent molecules. When non-stained, we achieved to detect the IR absorption of flavin molecules using auto-fluorescence. The microscopy is applicable to biochemical analysis inside cells based on molecular structure and thereby e.g. to cell selection.

DOI： 10.2530/jslsm.30.427

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A sensitive, real-time, and molecular-selective analyzer using a resonance-enhanced multiphoton ionization/time-of-flight mass spectrometer (REMPI-TOFMS) was combined with the chamber method to measure emission factors of VOCs during painting. Temporal variation of VOC emission was successfully captured on site on a second time scale. Exact and detailed assessment of emission is realized with molecular-dependent characteristics considered.

DOI： 10.1246/cl.2009.74

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We measured the infrared (IR) spectra of supersonically cooled N-phenylformamide (formanilide) and N-phenylacetamide (acetanilide) in the amide band and X-H stretch vibration regions by using IR-UV depletion spectroscopy combined with a newly developed mid-IR light source based on difference frequency generation in ZnGeP(2). The two rotational isomers, cis- and trans- of the amide group were separately monitored to record the IR spectra. Both of the conformers showed similar features in the amide I and II regions, while major differences of the isomers appeared in the amide III vibration region. The IR spectrum of trans-acetanilide closely resembles that of trans-formanilide, except for vibrations of the methyl group; that is, substitution of the formyl hydrogen to a methyl group has only a minor effect on the amide vibrations.

DOI： 10.1039/b822310f

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Language：English   Publishing type：Research paper (international conference proceedings)  

We demonstrated cell imaging without any stain by far-field 2-color infrared (IR) super-resolution microscopy, combining laser fluorescence microscope and picosecond transient fluorescence detected IR (TFD-IR) spectroscopy. TFD-IR spectroscopy detects IR absorption by monitoring fluorescence due to an electronic transition from a vibrational excited level by an additional visible light. By using the IR microscopy based on TFD-IR spectroscopy, the spatial resolution of the image can be increased to the visible diffraction limit of sub-μ m, i.e., the IR is super-resolved. Cell auto-fluorescence due to flavin molecules was monitored for label-free detection of the cellular components. The fluorescence image of an A549 cell was obtained by introducing both an IR light at 3300 nm and a visible light at 560 nm. The spatial resolution of the image was estimated to be 1.6 μ m. This is about 2.5-times higher resolution than the diffraction limit of IR light. The fluorescence intensity of the images at 3448 nm was smaller than that at 3300 nm, corresponding to the smaller IR absorption. Therefore, IR spectral imaging of a single cell was achieved with superresolution. © 2009 SPIE.

DOI： 10.1117/12.808903

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We demonstrated cell imaging without any stain by far-field 2-color infrared (IR) super-resolution microscopy, combining laser fluorescence microscope and picosecond transient fluorescence detected IR (TFD-IR) spectroscopy. TFD-IR spectroscopy detects IR absorption by monitoring fluorescence due to an electronic transition from a vibrational excited level by an additional visible light. By using the IR microscopy based on TFD-IR spectroscopy, the spatial resolution of the image can be increased to the visible diffraction limit of sub-mu m, i.e., the IR is super-resolved. Cell auto-fluorescence due to flavin molecules was monitored for label-free detection of the cellular components. The fluorescence image of an A549 cell was obtained by introducing both an IR light at 3300 nm and a visible light at 560 nm. The spatial resolution of the image was estimated to be 1.6 mu m. This is about 2.5-times higher resolution than the diffraction limit of IR light. The fluorescence intensity of the images at 3448 nm was smaller than that at 3300 nm, corresponding to the smaller IR absorption. Therefore, IR spectral imaging of a single cell was achieved with super-resolution.

DOI： 10.1117/12.808903

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Language：English   Publishing type：Research paper (international conference proceedings)  

A simple real-time measurement system for the components of volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs) in automobile exhaust gas using a laser ionization method was developed. This method was used to detect VOCs and PAHs in the exhaust gas of a diesel truck while idling, at 60 km/h, and in the Japanese driving mode JE05. As a result, various VOCs and PAHs, such as xylene and naphthalene, were simultaneously detected, and real-time changes in their concentration were obtained at 1 s intervals. Copyright © 2009 SAE International.

DOI： 10.4271/2009-01-1842

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Language：English   Publishing type：Research paper (international conference proceedings)  

Real-time analysis of benzene in automobile exhaust gas was performed using the Jet-REMPI (supersonic jet / resonance enhanced multi-photon ionization) method. Real-time benzene concentration of two diesel trucks and one gasoline vehicle driving in Japanese driving modes were observed under ppm level at 1 s intervals. As a result, it became obvious that there were many differences in their emission tendencies, because of their car types, driving conditions, and catalyst conditions. In two diesel vehicle, benzene emission tendencies were opposite. And, in a gasoline vehicle, emission pattern were different between hot and cold conditions due to the catalyst conditions. Copyright © 2009 SAE International.

DOI： 10.4271/2009-01-2740

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200805748

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The electronic spectrum of benzo[e]pyrene (BeP) was recorded using resonance-enhanced multi-photon ionization (REMPI) spectroscopy. A number of bands were observed and assigned to the origin band and vibronic bands of the S-1-S-0 transition. Ab initio calculations were performed to assign the vibrational structures in S-1. The origin band of BeP is well separated in energy from the origin band of benzo[a]pyrene (BaP), an isomer of BeP, and so BeP and BaP can be readily distinguished by the REMPI method, despite having the same mass.

DOI： 10.1246/cl.2008.1280

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Dispersed fluorescence and IR dip spectra of seven conformers of tyramine were measured in a supersonic jet. Observed vibrational bands are assigned based on quantum chemical calculations. The vibrational frequency of out-of-plane CH bending in the benzene ring shows characteristic shifts according to the conformation of C(beta)-C(alpha), while that of CH stretching in the methylene chain reflects the conformation of N-C(beta). From these vibrational frequencies, assignments of the conformers observed in the S(1)-S(0) laser induced fluorescence spectrum are discussed.

DOI： 10.1021/jp806232x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have recorded room temperature OH stretching overtone spectra of benzyl alcohol in the second and third overtone regions and jet-cooled OH stretching spectra in the fundamental and third overtone region. The spectra were recorded using photoacoustic and nonresonant ionization techniques, respectively. The spectra are characterized by a single band for each OH stretching overtone region suggesting the existence of one dominant stable conformer. In addition, our mass selected resonance enhanced multi photon ionization spectrum shows only one origin band. Ab initio calculations for benzyl alcohol yielded a lowest energy conformer adopting a gauche cis conformation around the alcoholic group, which is supported by our calculated OH stretching intensities. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2008.10.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The S-1-S-0 electronic spectra of 7-azaindole-(NH3)(n) clusters (n=1-3) were measured by mass-selected two-color resonance-enhanced multiphoton ionization spectroscopy. The laser-induced fluorescence spectrum obtained by monitoring the UV fluorescence shows well-structured vibrational bands for the monomer and 7-azaindole-(NH3)(1,2) clusters, while no signals appear for the 7-azaindole-(NH3)(3) cluster. The action spectrum obtained by monitoring visible emission shows no signal for all species, which suggests little reactivity for excited-state proton/hydrogen transfer. From the observed and calculated IR spectra, the geometry of 7-azaindole-(NH3)(1,2) was concluded to be a hydrogen-bonded bridge form, which is similar to the photochemically reactive 7-hydroxyquinoline-(NH3)(3) cluster. The difference in the photochemical reactivity is discussed on the basis of excited-state quantum chemical calculations. (c) 2008 American Institute of Physics.

DOI： 10.1063/1.2970936

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Spectroscopical Society of Japan  

We developed a supercritical fluid jet technique, which enables the vaporization and the jet-cooling of non-vola-tile molecules by supersonic expansion of their supercritical solutions to vacuum directly. For its purpose, a new high-pressure pulsed valve was developed. By using this pulsed valve, we could introduce the high-pressure fluid. over 25MPa into vacuum as a short gaseous pulse, and confirmed that we can obtain an enough jet-cooling condi-tion. In this review, we will introduce a detail of the high-pressure pulsed valve and its application for the super-critical fluid jet spectroscopy.

DOI： 10.5111/bunkou.57.158

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

We have developed a tunable, narrow-bandwidth (< 2 cm(-1)) mid-infrared (MIR) optical parametric system with a large-aperture periodically poled Mg-doped LiNbO3 (LA-PPMgLN)-based high-energy pump source. The system has a continuously tunable tuning range from 4.6 to 11.2 mu m and produces a maximum output energy of 2.0 mJ at 5.1 mu m. Practical use of the MIR source is demonstrated by MIR-UV double-resonance spectroscopy of jet-cooled acetanilide. (c) 2008 Optical Society of America.

DOI： 10.1364/OL.33.001699

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Language：English   Publishing type：Research paper (scientific journal)  

We demonstrated super-resolution microscopy using a high numerical aperture (NA) oil immersion lens in acute optical alignment condition. In super-resolution microscopy, the pump beam is overlapped together with a doughnut-shaped erase beam in the focal plane, and fluorescence emission from the overlapping area is prevented. Alignment accuracy of these two beams determines the image properties of the microscope. Scanning fluorescence micro-beads in the focal plane, we confirmed the beam shape and its center position for the pump and erase beams respectively. Owing to the adjustment, we achieved a point-spread function with FWHM finer than 100 nm at least, which is predicted by the theory of super-resolution microscopy. © 2008 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2008.175

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The performance of a fluorescence depletion microscope system depends critically on the precise alignment of both the pump and the erase beams with the axis of the focusing objective lens. In this article we propose a technique with which the need for separate alignment of the pump and erase beams is eliminated. Besides being insensitive to alignment errors, our technique is much more compact than present systems, and can serve as a basis for a commercial fluorescence depletion microscope. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2007.05.069

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DOI： 10.2116/bunsekikagaku.57.227

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Molecular Science  

Resonant enhanced multiphoton ionization spectroscopy with a supersonic jet is an established method for molecular science. This familiar tool has an another possibility for chemical analysis by its resonant effect; real-time, highly sensitive analysis without pretreatment. The real-time chemical analysis is demonstrated for benzene in the automobile exhaust gas. Further extension to the history analyzer for a single suspended particulate matter is also introduced briefly.

DOI： 10.3175/molsci.2.A0026

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

For monitoring of hazardous organic compounds, we have been developing an on-line analytical instrument based on a supersonic jet resonance enhanced multi-photon ionization (REMPI) mass spectrometry. We have attempted to apply this technique to monitor transient emission phenomena of hazardous organic compounds in exhaust gas. It has been proven to be possible to conduct real-time monitoring of gaseous compounds in the atmosphere by our instrument with continuous sample introduction. We demonstrated that the signals of monochlorobenzene in a chimney could be detected. Also the delay time between gas emission and detection through a 23 m long stainless-steel pipe kept at 200 degrees Celsius was 150 seconds. It was proven that there were two different kinds of emission mechanisms of monochlorobenzene in the chimney.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本工業出版  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A series of bipyridyl-Pd and Rh complexes containing a [(bpy)(3)Ru](2+) or [(bpy)(2)Ru(phen)](2+) (bpy = 2,2&apos;-bipyridyl, phen = 1,10-phenanthroline) moiety as visible-light absorbing unit was synthesized. The complexes were synthesized via a Suzuki-Miyaura coupling reaction between the Ru complexes having a 4-bromo-2,2&apos;-bipyridyl ligand and a 2,2&apos;-bipyridyl-4-boronic acid and a subsequent reaction with various mononuclear Pd and Rh precursors. There was a noticeable structural difference between the QP (2,2&apos;:4&apos;,4 &apos;&apos;:2 &apos;&apos;,2"&apos;-quaterpyridyne) and PB (5-(2,2&apos;-bipyridyl)-yl-1,10-phenanthroline) complexes, which involved the dihedral angles within the bridging ligand; the PB complexes possessed large dihedral angles but the QP complexes showed small values. This structural difference clearly indicated a strong pi-conjugation through the QP ligand. The electrochemical and photophysical properties of the QP and PB complexes were compared with the parent mononuclear Ru complexes, such as [(bpy)(3)Ru](2+), [(bpy)(2)Ru(phen)](2+), and [(bpy)(2)Ru(bpm)](2+) (bpm = 2,2&apos;-bipyrimidine). The QP and PB complexes showed a (MLCT)-M-3 life time that was similar to [(bpy)(3)Ru](2+) and [(bpy)(2)Ru(phen)](2+), which was about 10 times longer (ca. 1 mu s) than the corresponding bpm complexes. Reactivity studies with Pd complexes toward styrene dimerizations were examined. The reaction proceeded under visible-light irradiated conditions and the reactivity of the QP complexes was much higher than the corresponding PB complexes. Substantial acceleration of the reaction was observed with the introduction of an Me substituent on the bipyridyl ligand.

DOI： 10.1039/b809020c

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Language：English   Publisher：The Biophysical Society of Japan General Incorporated Association  

DOI： 10.2142/biophys.48.S178_5

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Transient fluorescence detected infrared (TFD-IR) microscopy was developed to overcome the diffraction limit of infrared (IR) light without a near-field system. This microscopic technique is based on TFD-IR spectroscopy, which converts information on IR absorption to fluorescence intensity by further electronic excitation of vibrationally excited molecules by a probing UV/visible light. Roots of Arabidopsis thaliana and living A549 cells with fluorescent dyes were chosen as samples. In the measurements using the TFD-IR microscope, tunable IR picosecond laser pulses were used in the wavelength range from 2700 to 3700 nm, corresponding to CH, NH, and OH stretching modes. Fluorescence images of the root cells of A. thaliana by the TFD-IR scheme were obtained with super-resolution compared with the resolution of conventional IR microscopy. The resolution is estimated to be less than 2.6 urn by fitting of a gaussian function. However, the TFD-IR images were dominated mainly by the fluorescent dyes because they were almost the same as a conventional fluorescence image. To investigate other contributions hidden by that of fluorescent dyes, we plotted the fluorescence intensity in several 5 μm squares at various IR wavelengths, called a TFD-IR spectrum. For root cells of A. thaliana, the TFD-IR spectra show shapes similar to those of a conventional IR absorption spectrum of the fluorescent dye. Therefore, the TFD-IR images are not due to the cellular components. For an A549 cell, the TFD-IR spectra were different from a conventional IR absorption spectrum of fluorescent dyes in the wavelength region shorter than 3100 nm. We speculate that the spectral difference is due to the cellular components, possibly assigned to the combination band related to amino groups of cellular components bonded covalently to the fluorescent dyes.

DOI： 10.1117/12.762980

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Publishing type：Research paper (international conference proceedings)  

Time-resolved measurements of volatile organic compounds (VOC) and poly aromatic hydrocarbon (PAH) in exhaust gas from automobiles in a driving mode have been performed using Supersonic Jet / resonance enhanced multi-photon ionization (Jet-REMPI) method with 10 ppb sensitivity. Benzene, naphthalene and phenol were measured before and after catalyst treatment in the diesel cars. At the same time total hydrocarbon (THC) was detected by FID through a CVS instrument, which is the normal method for real-time measurement of hydrocarbon without distinction of hydrocarbon species in exhaust gas. The changes in concentration of benzene and other PAH corresponding to the changes in the driving mode were successfully measured every 1 second. As a result of real-time monitoring of exhaust gas from diesel engine, benzene, naphthalene and phenol were quantified at JE05 mode. Compared a real-time PAH and VOC signals with a total hydrocarbon signal detected by FID, it was found that each tendency of benzene and naphthalene was almost same as that of THC, while the tendency of phenol is different from that of THC. Copyright © 2008 by the Japan Society of Mechanical Engineers.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Transient fluorescence detected infrared (TFD-IR) microscopy was developed to overcome the diffraction limit of infrared (IR) light without a near-field system. This microscopic technique is based on TFD-IR spectroscopy, which converts information on IR absorption to fluorescence intensity by further electronic excitation of vibrationally excited molecules by a probing UV/visible light. Roots of Arabidopsis thaliana and living A549 cells with fluorescent dyes were chosen as samples. In the measurements using the TFD-IR microscope, tunable IR picosecond laser pulses were used in the wavelength range from 2700 to 3700 nm, corresponding to CH, NH, and OH stretching modes. Fluorescence images of the root cells of A. thaliana by the TFD-IR scheme were obtained with super-resolution compared with the resolution of conventional IR microscopy. The resolution is estimated to be less than 2.6 mu m by fitting of a gaussian function. However, the TFD-IR images were dominated mainly by the fluorescent dyes because they were almost the same as a conventional fluorescence image. To investigate other contributions hidden by that of fluorescent dyes, we plotted the fluorescence intensity in several 5 mu m squares at various IR wavelengths, called a TFD-IR spectrum. For root cells of A. thaliana, the TFD-IR spectra show shapes similar to those of a conventional IR absorption spectrum of the fluorescent dye. Therefore, the TFD-IR images are not due to the cellular components. For an A549 cell, the TFD-IR spectra were different from a conventional IR absorption spectrum of fluorescent dyes in the wavelength region shorter than 3 100 nm. We speculate that the spectral difference is due to the cellular components, possibly assigned to the combination band related to amino groups of cellular components bonded covalently to the fluorescent dyes.

DOI： 10.1117/12.762980

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We have developed a tunable, narrow-bandwidth (~2cm-1) Mid-IR optical parametric system with a large-aperture PPMgLN based pump source. The system tuned from 4.7 to 10.6μm, and the maximum output energy of 1.7mJ was obtained. © 2008 Optical Society of America.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We have developed a narrow-bandwidth (&lt;2cm(-1)) Mid-IR optical parametric system with a large-aperture PPMgLN based 2 mu m pump system. The system tuned from 4.7 to 10.6 mu m, and the maximum output energy of 1.7mJ was obtained. (C)2008 Optical Society of America.

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Language：English   Publishing type：Research paper (international conference proceedings)  

Supersonic jet/resonance enhanced multi-photon ionization (Jet-REMPI) technique was focused on the analyzing method for gas mixture like exhaust gas from automobiles. In this method, when the mass number and wavelength of excitation laser are determined adequately, the target compound can be monitored selectively. We developed a new analyzer utilizing REMPI method. Using this analyzer, real-time monitoring of exhaust gas from a motorcycle and diesel vehicles was conducted. As a result of real-time monitoring test of the vehicles, concentrations of aromatic compounds like benzene toluene etc. were quantified and real-time changes of their concentrations were observed. © 2007 SAE International.

DOI： 10.4271/2008-01-0761

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DOI： 10.2116/bunsekikagaku.56.1133

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DOI： 10.3131/jvsj.50.745

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The picosecond time-resolved IR spectra of phenol/ammonia (1:3) cluster were measured by UV-IR-UV ion dip spectroscopy. The time-resolved IR spectra of the reaction products of the excited state hydrogen transfer were observed. From the different time evolution of two vibrational bands at 3180 and 3250 cm(-1), it was found that two isomers of hydrogenated ammonia radical cluster center dot NH(4)(NH(3))(2) coexist in the reaction products. The time evolution was also measured in the near-IR region, which corresponds to 3p-3s Rydberg transition of center dot NH(4)(NH(3))(2); a clear wavelength dependence was found. From the observed results, we concluded that (1) there is a memory effect of the parent cluster, which initially forms a metastable product, center dot NH(4)-NH(3)-NH(3), and (2) the metastable product isomerizes successively to the most stable product, NH(3)-center dot NH(4)-NH(3). The time constant for OH cleaving, the isomerization, and its back reaction were determined by rate-equation analysis to be 24, 6, and 9 ps, respectively.

DOI： 10.1063/1.2806182

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

In thermal processes, such as combustion and pyrolysis reactions, the development of useful techniques for the real-time monitoring of organic compounds, like dioxin and polycyclic aromatic hydrocarbons (PAHs), has been demanded. Supersonic jet resonance enhanced multi-photon ionization time-of-flight mass spectrometry (Jet-REMPI-TOFMS) has been an effective technique in terms of the molecular selectivity, high sensitivity, and real-time analysis capability of those compounds. In this study, we developed a prototype Jet-REMPI-TOFMS system. We tried to carry out real-time observations of the naphthalene emission behavior for heated coal samples in an inert gas flow using an electric tube furnace. The behavior of naphthalene emission on the coal pyrolysis reaction was different among the types of coal species. For example, one coal sample that is used as a coking material, naphthalene, began to appear from 170 C, previously to the generation of methane and ethane, and finished at above 600 C. It is suggested that naphthalene is formed by breaking the naphthyl group contained in thermally unstable sites of coals.

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A nonscanning two-color infrared super-resolution microscope combining a laser fluorescence microscope and picosecond time-resolved transient fluorescence detected IR (TFD-IR) spectroscopy has been developed. Picosecond time-resolved infrared super-resolution images were obtained with 2ps time resolutions and 1.4 μm spatial resolutions, without XY scanning of the sample or the excitation light of infrared and visible. A demonstration measurement on Arabidopsis thaliana roots labeled by Rhodamine 6G is presented. Copyright © 2007 The Chemical Society of Japan.

DOI： 10.1246/cl.2007.1380

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Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

We have demonstrated a simple, high-energy, narrow spectral bandwidth optical parametric oscillator (OPO) by use of a large aperture periodically poled Mg-doped LiNbO3 device with a volume Bragg grating (VBG). A free-running degenerate OPO pumped by a Q-switched 1.064 mu m Nd:YAG laser exhibits maximum output pulse energy of 110 mJ with high slope efficiency of 75% around room temperature. Broad spectral bandwidth (Delta lambda similar to 100 nm) around the degeneracy wavelength was suppressed by using a VBG as an output coupler. Up to 61 mJ of the output pulse energy with narrowed spectral bandwidth of less than 1.4 nm was obtained at the degeneracy wavelength of 2.128 mu m. (C) 2007 Optical Society of America

DOI： 10.1364/OL.32.002996

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

IR spectra of phenol-Ar-n (PhOH-Ar-n) clusters with n=1 and 2 were measured in the neutral and cationic electronic ground states in order to determine the preferential intermolecular ligand binding motifs, hydrogen bonding (hydrophilic interaction) versus pi bonding (hydrophobic interaction). Analysis of the vibrational frequencies of the OH stretching motion, nu(OH), observed in nanosecond IR spectra demonstrates that neutral PhOH-Ar and PhOH-Ar-2 as well as cationic PhOH+-Ar have a pi-bound structure, in which the Ar atoms bind to the aromatic ring. In contrast, the PhOH+-Ar-2 cluster cation is concluded to have a H-bound structure, in which one Ar atom is hydrogen-bonded to the OH group. This pi -&gt; H binding site switching induced by ionization was directly monitored in real time by picosecond time-resolved IR spectroscopy. The pi-bound nu(OH) band is observed just after the ionization and disappears simultaneously with the appearance of the H-bound nu(OH) band. The analysis of the picosecond IR spectra demonstrates that (i) the pi -&gt; H site switching is an elementary reaction with a time constant of similar to 7 ps, which is roughly independent of the available internal vibrational energy, (ii) the barrier for the isomerization reaction is rather low(&lt; 100 cm(-1)), (iii) both the position and the width of the H-bound nu(OH) band change with the delay time, and the time evolution of these spectral changes can be rationalized by intracluster vibrational energy redistribution occurring after the site switching. The observation of the ionization-induced switch from pi bonding to H bonding in the PhOH+-Ar-2 cation corresponds to the first manifestation of an intermolecular isomerization reaction in a charged aggregate. (c) 2007 American Institute of Physics.

DOI： 10.1063/1.2775935

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Phenol(+)-Kr cations (PhOH+-Kr) generated by photoionization (REMPI) of the neutral complex and in an electron ionization (El) source were assayed by their infrared (IR) spectra in the OH stretch (nu(OH)) range. Two isomers are identified in the EI-IR spectrum by their Delta nu(OH) complexation shifts: the more stable H-bound global minimum (Delta nu(OH) = -123 cm(-1)) and the less stable pi-bound local minimum (Delta nu(OH) = +1 cm(-1)). The REMPI-IR spectrum reveals VOH absorptions assigned to cold pi-bound complexes and hot H-bound dimers. The latter are generated via it H isomerization after the ionization of neutral pi-bound dimers. EI-IR spectra are also presented for PhOH+-Kr-2. Quantum chemical calculations support the interpretation of the spectroscopic data. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2007.06.103

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The hole-burning (HB) spectra of phenol-Ar-n (PhOH-Ar-n) clusters with n = 1 and 2 have been measured in a molecular beam to clarify the possible existence of isomers. Two species were identified to give rise to signals in the S-1-S-0 spectrum recorded for the n = 1 cluster; however, one of the species was found to originate from dissociation of an n = 2 cluster. Similarly, three species were observed in the spectrum of the n = 2 cluster, and two of them were assigned to n = 3 and larger clusters. The spectral contamination from larger size clusters was quantitatively explained by the dissociation after photoexcitation. The analysis of the spectra demonstrates that only a single isomer exists in the molecular beam for both the n = 1 and the n = 2 clusters. In addition to two previously detected intermolecular modes, a third low-frequency mode, assigned to an intermolecular bending vibration, is observed for the first time in the HB spectrum of the n = 2 cluster. The assignments of the intermolecular vibrations were confirmed by ab initio MO calculations. The observation of the third intermolecular vibration suggests that the geometry of the n = 2 cluster has C-s or lower symmetry.

DOI： 10.1021/jp070787g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

The vectorial Debye integral shows that tightly focused Laguerre-Gaussian (LG) beams have a residual intensity at the focal point for linear polarization, for a topological charge of m = 1 and 2. We measured the shapes of linearly and circularly polarized LG beams and found that a central intensity appeared at m = 1 and 2 for linear and right-handed circular polarization, however, it is completely canceled for left-handed circular polarization. In general, when the orbital angular momentum of the LG beam is parallel to the spin angular momentum of the photons, zero intensity is always achieved at the focus. (C) 2007 Optical Society of America.

DOI： 10.1364/OL.32.002357

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have measured the OH-stretching fundamental and overtone spectra of resorcinol and hydroquinone in a supersonic jet using nonresonant ionization detected infrared/near-infrared spectroscopy. Anharmonic oscillator local mode calculations of the OH-stretching frequencies and intensities and Boltzmann populations of the stable rotamers have been calculated at the B3LYP/6-311++G(3df,2pd) level to help interpret the observed spectra. Resorcinol has three stable rotamers and in the recorded second and third OH-stretching overtone spectra there is evidence of two distinguishable rotamers. Hydroquinone has two stable rotamers; however, the OH-stretching oscillators of each rotamer are so similar in nature that even up to the fourth OH-stretching overtone the transitions coincide. These results place a limit on the ability of the jet-cooled overtone spectroscopy technique to distinguish between rotamers.

DOI： 10.1021/jp071677c

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Language：English   Publishing type：Research paper (scientific journal)  

We report on the first successful output of electrons directly from photosystem I (PSI) of thermophilic cyanobacteria to the gate of a field-effect transistor (FET) by bypassing electron flow via a newly designed molecular wire, i.e., artificial vitamin K(1), and a gold nanoparticle; in short, this newly manufactured photosensor employs a bio-functional unit as the core of the device. Photo-electrons generated by the irradiation of molecular complexes composed of reconstituted PSI on the gate were found to control the FET. This PSI-bio-photosensor can be used to interpret gradation in images. This PSI-FET system is moreover sufficiently stable for use exceeding a period of 1 year.

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We report on the first successful output of electrons directly from photosystem I (PSI) of thermophilic cyanobacteria to the gate of a field-effect transistor (FET) by bypassing electron flow via a newly designed molecular wire, i.e., artificial vitamin K-1, and a gold nanoparticle; in short, this newly manufactured photosensor employs a bio-functional unit as the core of the device. Photo-electrons generated by the irradiation of molecular complexes composed of reconstituted PSI on the gate were found to control the FET. This PSI-bio-photosensor can be used to interpret gradation in images. This PSI-FET system is moreover sufficiently stable for use exceeding a period of I year. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.bbabio.2006.11.008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A new far-field infrared super-resolution microscopy combining laser fluorescence microscope and picosecond time-resolved transient fluorescence detected IR (TFD-IR) spectroscopy is proposed. TFD-IR spectroscopy is a kind of IR-visible/UV double resonance spectroscopy, and detects IR transitions by the transient fluorescence due to electronic transition originating from vibrationally excited level populated by IR light. IR images of rhodamine-6G solution and of fluorescent beads were clearly observed by monitoring the transient fluorescence. Super-resolution twice higher than the diffraction limit for IR light was achieved. The IR spectrum due to the transient fluorescence was also measured from spatial domains smaller than the diffraction limit. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2007.03.035

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Vacuum Society of Japan  

DOI： 10.3131/jvsj.50.241

CiNii Books

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Other Link： https://jlc.jst.go.jp/DN/JALC/00293460697?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The dependence of fluorescence depletion on the relative polarizations of pump and erase beams is investigated for a sample of randomly oriented Rhodamine-6G molecules. The significance of polarization effects is illustrated for two existing systems of fluorescence depletion super-resolution microscopy: a circular polarization setup, and an azimuth-linear polarization setup. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2006.11.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The structure of a jet-cooled 1-naphthol (1-NpOH) dimer was investigated by using resonant-enhanced two-photon ionization (R2PI) and ion-detected infrared (IR) dip spectroscopy. A geometrical optimization and a frequency calculation in (1-NpOH)(2) were also performed at the MP2/cc-pVDZ level. Stable isomers in the MP2/cc-pVDZ calculation were classified into a structure dominated only by the pi-pi interaction and structures formed by cooperation between the pi-pi interaction and hydrogen bonding. On the basis of a comparison between the observed and calculated IR spectra, the geometry of (1-NpOH)(2) was concluded to be a pi-pi stacking structure supported by hydrogen bonding.

DOI： 10.1021/jp0668910

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC APPLIED SPECTROSCOPY  

The contrast transfer function (CTF) of super-resolution microscopy was quantitatively investigated using a fluorescent scale. The scale has minute fluorescent line patterns, finer than 100 nm, and is suitable for measuring CTF in super-resolution microscopy. The measured CTF shows that super-resolution microscopy can indeed improve the optical properties of fluorescent images and enable us to observe a structure with the spatial resolution overcoming the diffraction limit. From the CTF, it has been found that super-resolution microcopy can resolve a 100 nm line-and-space pattern and provides a contrast of 10%. The CTF corresponds to a PSF with a full-width at half-maximum (FWHM) of 130 run. An evaluation using a 100 nm phi fluorescent bead consistently supports the results given by the CTF for super-resolution microscopy.

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Language：English   Publishing type：Research paper (international conference proceedings)  

We quantitatively investigated image properties in super-resolution microscopy using two-color fluorescence dip spectroscopy. To evaluate the properties, the point spread function (PSF) and contrast transfer function (CTF) were measured using a fluorescent scale together with a fluorescent bead. From the CTF, it has been found that visible light can resolve a 100 nm line-and-space pattern by microcopy, and provide a contrast of 10%. The CTF corresponds to a PSF with a FWHM of 130 nm. The value is two times finer than the diffraction limit size. An evaluation using a 100 nm φ fluorescent bead consistently supports the result given by the CTF for super-resolution microscopy. The measured CTF shows that super-resolution microscopy can indeed improve the optical properties of fluorescent images and enable us to observe a structure with a spatial resolution overcoming the diffraction limit.

DOI： 10.1117/12.698451

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Language：English  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We report a large aperture periodically poled MgO:LiNbO3 optical parametric system with Bragg grating. Narrow bandwidth pulses of &lt;1nm at degeneracy point (2.128 mu m) were amplified up to 30mJ. (C) 2007 Optical Society of America

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We quantitatively investigated image properties in super-resolution microscopy using two-color fluorescence dip spectroscopy. To evaluate the properties, the point spread function (PSF) and contrast transfer fuNction (CTF) were measured using a fluorescent scale together with a fluorescent bead. From the CTF, it has been found that visible light can resolve a 100 mn line-and-space pattern by microcopy, and provide a contrast of 10%. The CTF corresponds to a PSF with a FWHM of 130 mn. The value is two times finer than the diffraction limit size. An evaluation using a 100 run 0 fluorescent bead consistently supports the result given by the CTF for super-resolution microscopy. The measured CTF shows that super-resolution microscopy can indeed improve the optical properties of fluorescent images and enable us to observe a structure with a spatial resolution overcoming the diffraction limit.

DOI： 10.1117/12.698451

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Publishing type：Research paper (international conference proceedings)  

We have developed a high-energy (>30mJ), narrow-bandwidth (<2nm) optical parametric system with large-aperture PPMgLN devices. The optical parametric system was employed in a ZnGeP2 difference frequency generation system and tunable mid-infrared generation was observed. © 2007 Optical Society of America.

Scopus

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

To reduce a measurement time in scanning microscope using pulse laser light source, we developed a novel measurement system. In the system, address data of sample stage signal are detected together with a sign from a sample. Using this system, a fluorescence image of a nano-scale with 250nm L&amp
S line pattern was measured with a positioning accuracy of 40nm. A contrast of the image with 100×100 pixels corresponds to that for the diffraction limit of an objective lens. It takes only 20 sec for obtaining one image with a good S/N. It is expected the system contribute to microscopy applied in a research field concerning nano-science.

DOI： 10.1541/ieejeiss.127.1344

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Publishing type：Research paper (scientific journal)  

We have demonstrated efficient, high-energy, narrow-spectral-bandwidth 2.128 μm pulse generation by use of periodically poled MgO : LiNbO 3 devices with a 36 mm length and a 5 mm × 5 mm large aperture. A free-running degenerated optical parametric oscillator (OPO) pumped with a Q-switched 1.064 μm Nd:YAG laser exhibits a high slope efficiency of 75% and an optical-to-optical conversion efficiency of 70% with a broad spectral bandwidth (>100 nm). In a configuration with a spectrally narrowed master oscillator followed by a power amplifier, we have achieved an output pulse energy of 52 mJ with a spectral bandwidth of less than 2 nm at the degeneracy point. The total optical-to-optical conversion efficiency of the system reached 50%. © 2006 Optical Society of America.

DOI： 10.1364/OL.31.003149

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A new supersonic jet technique, for nonvolatile and pyrolytic molecules, such as biomolecules, called the supercritical fluid jet (SCF-jet) technique was developed. This method enables the vaporization of such molecules without hard heating. To demonstrate the SCF-iet technique, we applied it to1-naphthol and measured the resonant enhanced multiphoton ionization spectrum.

DOI： 10.1246/cl.2006.1044

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The structures of the naphthalene monomer and dimer were investigated with performing vibrational analysis. The MP2 optimization showed that the naphthalene monomer has a nonplanar geometry in the 6-31G, 6-31G*, 6-31+G*, and 6-311G basis sets, while it has a planar geometry in the 6-31G*(0.25) and Dunning's correlation consistent basis sets. The MP2/cc-pVDZ calculation showed the presence of the four stable isomers, which were part of the isomers in the previous MP2/6-31G* calculation ( Walsh, T. R. Chem. Phys. Lett. 2002, 363, 45). The presence of extra structures in the MP2/6-31G* calculation is attributed to a poor description of the potential energy surface, which is evident from the nonplanar structure of the monomer in the MP2/6-31G* calculation. The relative stability among the isomers in the MP2/cc-pVDZ calculation without counterpoise correction was maintained in both the single-point calculation at the MP2/aug-cc-pVDZ//MP2/cc-pVDZ level and the counterpoise-corrected optimization at the MP2/cc-pVDZ level. The relative stability among the isomers suggested an enhancement of the pi-pi interaction in the structure with lower symmetry, which could be explained using a molecular-orbital model. The vibrational analysis in MP2/cc-pVDZ without the counterpoise correction suggested that the isomers of the naphthalene dimer were distinguishable by the observation of the infrared spectrum in the low-frequency region (150-600 cm(-1)).

DOI： 10.1021/ct050278n

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have measured the OH- and OD-stretching fundamental and overtone spectra of phenol and its deuterated isotopomers under jet-cooled conditions using nonresonant ionization detection spectroscopy and vapor-phase infrared (IR) and near-infrared (NIR) spectra at room temperature using conventional and photoacoustic spectroscopy. The OH- and OD-stretching bands in the jet-cooled spectra are about 1-10 cm(-1) wide and generally show a few Lorentzian shaped peaks. The bands in the room-temperature spectra have widths of 20-30 cm(-1) and display clear rotational profiles. The band profiles in the jet-cooled spectra arise mostly from nonstatistical intramolecular vibrational redistribution (IVR) with specific coupling to "doorway" states, which are likely to involve CH- and CD-stretching vibrations. The transition dipole moment that determines the rotational structure is found to rotate significantly from the fundamental to the third overtone and is not directed along the OH(D) bond. We use these calculated transition dipole moments to simulate the rotational structure. We determine the rotational temperature in the jet-cooled spectra to be about 0.5 K. Anharmonic oscillator local mode calculations of frequencies and intensities of the OH- and OD-stretching transitions are compared with our measured results. The calculated intensities are in good agreement with the absolute intensities obtained from conventional spectroscopy and with the relative intensities obtained from the room-temperature laser spectroscopy.

DOI： 10.1021/jp060723q

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We constructed a super-resolution microscope system based on a cw laser light source. Electro-optical modulators convert the cw laser light into a light pulse with a width of 15 ns and provide a repetition rate of 100 kHz. The performance of the microscope was evaluated using 100 nm phi fluorescence microbeads. The fluorescence signal from the beads can be detected with very low statistical fluctuation. The super-resolution image was obtained with better signal to noise ratio compared with that given by a pulse laser light source with a repetition rate of several tens of hertz. The fluorescent size of the beads was 150 nm, which is 2.3 times smaller than the diffraction limit. Experimental results confirmed that the two-point resolution also overcomes the diffraction limit. The constructed system is expected to become a commercial microscope.

DOI： 10.1063/1.2213213

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have achieved high average power Raman output from a compact, diode-pumped, self-stimulating Nd3+:KGd(WO4)(2) Raman laser. Maximum Raman output power of 0.8 W was achieved at a pulse repetition frequency (PRF) of 2 kHz. The optical efficiency from diode to Raman laser was 14%. By generating extra-cavity second harmonics using a LiB3O5 crystal, it was possible to produce 0.2 W yellow output. The laser system was simulated numerically using rate equations and the results obtained were in good agreement with the experimental results. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2005.11.023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The two-color fluorescence depletion process of Rhodamine 6G in PMMA matrixes was investigated using nano- and picosecond lasers. Erase-lasers of 1064 and 599 nm depleted the fluorescence from the S, state. Fluorescence depletion with 1064 nm was analyzed by the up-conversion from state S, to S,, while that with 599 nm was simulated based on both the up-conversion and the stimulated emission. A three-state model describes this process due to a nanosecond laser well, while it could not reproduce that by picosecond lasers. Significant contributions of vibrational relaxation in S, and re-absorption from So are suggested in the picosecond region. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2005.12.020

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Two-color (1 + 1') REMPI mass spectra of o-, m- and p-fluorophenol . ammonia (1 : n) clusters were measured with a long delay time between excitation and ionization lasers. The appearance of NH4(NH3)(n-1)(+) with 100 ns delay after exciting the S-1 state is a strong indication of generation of long-lived species via S1. In analogy with the phenol . ammonia clusters, we conclude that an excited state hydrogen transfer reaction occurs in o-, m- and p-fluorophenol (.) ammonia clusters. The S-1-S-0 transition of o-, m- and p-fluorophenol (.) ammonia ( 1 : 1) clusters were measured by the ( 1 + 10) REMPI spectra, while larger ( 1 : n) cluster (n = 2-4) were observed by monitoring the long-lived NH4(NH3)(n-1) clusters action spectra. The vibronic structures of m- and p-fluorophenol . ammonia clusters are assigned based on vibrational calculations in S-0. The o-fluorophenol (.) ammonia (1 : 1) cluster shows an anharmonic progression that is analyzed by a one-dimensional internal rotational motion of the ammonia molecule. The interaction between the ammonia molecule and the fluorine atom, and its change upon electronic excitation are suggested. The broad action spectra observed for the o-fluorophenol (.) ammonia (1 : n) cluster (n &gt;= 2) suggest the excited state hydrogen transfer is faster than in m- and p-fluorophenol (.) ammonia clusters. The different reaction rates between o-, m- and p-fluorophenol (.) ammonia clusters are found from comparison between the REMPI and action spectra.

DOI： 10.1039/b511619h

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Publishing type：Research paper (international conference proceedings)  

We report an optical parametric oscillator/power amplifier using periodically poled MgO:LiNbO3 with 38 mm length and 5×5mm 2 large aperture. We achieved output energy of 52mJ with spectral bandwidth of <2nm at degeneracy point (2.128μm). ©2006 Optical Society of America.

DOI： 10.1109/CLEO.2006.4627994

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：エヌ・ティー・エス  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

The focal intensity distribution of strongly focused (NA=0.9) first-order Laguerre-Gaussian doughnut beams is investigated experimentally for three different polarizations: linear, and left-handed circular and right-handed circular. The investigations are done by 2-dimensional scanning the focal plane with of a 100nm diameter fluorescent microbead, and measuring the fluorescence signal. The results are shown to be in excellent agreement with theoretical predictions, and demonstrate the superiority of one of the circular polarizations to achieve a sharp dark central spot. (c) 2005 Optical Society of America.

DOI： 10.1364/OPEX.13.010440

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：化学同人  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A series of dendritic phenylazomethines (DPA), which have a meso-substituted zinc porphyrin core (DPAGX-ZnP, X = 1-4), were synthesized. Structural studies of these dendrimers were carried out using Tri-SEC (triple detection after size exclusion chromatography), intrinsic viscosity analysis, TEM (tunneling electron microscopy), and molecular modeling calculations by AM1. As a result, a sphere-like structure within a single-nanometer scale (R-h = 22 angstrom for DPAG4-ZnP) was observed. In addition, encapsulating effects by the DPA shell in the larger dendrimers were confirmed as fundamental properties, based on the UV-vis abosorption spectra, cyclic voltammograms, and H-1 NMR spin-lattice relaxation times (T-1). The DPAGX-ZnP acts as a multi-metal ion reservoir for SnCl2 and FeCl3. The generation-4 dendrimer (DPAG4-ZnP) can take up to 60 molar amounts of metal complexes around the porphyrin core. A quantitative study of the metal assembling reaction by UV-vis titration revealed stepwise layer-by-layer complexations from the inner imines nearest to the core to the surface. The redox behavior and fluorescence of the zinc porphyrin in these metal-assembled clendrimers also support the stepwise complexation of the metal ion. These analyses suggest that the finely assembled metal complexes in a dendrimer architecture strongly affect the electronic status of the porphyrin core. Results from transient absorption measurements strongly indicate a very fast electron transfer on a subpicosecond time scale between the core and assembled metal complexes.

DOI： 10.1021/ja0524797

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

For the analysis of trace amounts of hazardous organic compounds, we developed a new ion detection system for supersonic jet resonance-enhanced multiphoton laser ionization mass spectrometry. High sensitivity and selectivity have been achieved by combining a proto-type Daly detector, a newly designed conical ion lens, and a potential switch that can perform the function of a mass selector. This ion detection system enables us to bring the jet nozzle closer to the ionization point. The detection sensitivity has thus been improved totally by more than 100 times compared with that obtained by the parallel-plate electrodes and micro-channel plate. We succeeded in assembling a flangeon-type ion extraction electrode consisting of a conical ion lens and a potential switch.

DOI： 10.2116/analsci.21.991

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

To establish a calibration method of optical performance in fluorescence microscopy, we fabricated a fluorescent nanometer-scale marker by combining a dry dye method for polymer film and fine lithography. The marker has a 50 nm line-and-space fluorescent pattern, finer than the optical diffraction limit. A spin-coated poly(methyl methacrylate) thin film on a silicon wafer was densely doped with Rhodamine 6G using a simple vacuum process, named the vapor-transportation method, and then the pattern was formed on the film using electron-beam lithography. The figure accuracy of the fabricated marker was calibrated by electron microscopes. Using this marker, one can quantitatively evaluate the optical properties; i.e., the contrast-transfer function, the point-spread function, magnification, and so on. To show practical use of the marker, we demonstrated the evaluation of a fluorescent microscope system. (c) 2005 American Institute of Physics.

DOI： 10.1063/1.1946627

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC APPLIED SPECTROSCOPY  

The two-point resolution of a novel two-color far-field super-resolution fluorescence microscopy was evaluated by measuring fluorescent beads 100 nm in diameter. This microscopy is based on a combination of two-color fluorescence dip spectroscopy and a phase-modulation technique for a laser beam. By simply introducing two-color laser light, the size of the fluorescent image of a bead was shrunk down to a diameter of 250 run from the diffraction-limited image with a diameter of 360 nm. For two closely adjacent fluorescent beads with a separation distance of 350 nm, the two-color microscope clearly gave separated fluorescence images, while the conventional one-color fluorescence microscope could not resolve them. It has been proved that our technique breaks Rayleigh's diffraction limit.

DOI： 10.1366/0003702054411562

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

The profile of the point spread function (PSF) in superresolution microscopy is studied theoretically. The fluorescence spot profile (i.e., the PSF) is determined by the focused beam patterns of the applied two-color lasers and the optical properties of the fluorescence-depletion process induced by the lasers (the pump and erase beams). In this study, the fluorescence-depletion process for the sample molecule is analyzed using a rate equation for a three-state model. Based on this result, we calculate the PSF for the case where the erase beam is modeled by a first-order Bessel function. In the case of an erase beam with a large photon flux, the obtained PSF has a Lorentzian-like shape, which seldom appears in traditional microscopy. In this work, we also investigated a possible relationship between the PSF and other parameters in the fluorescence-depletion process. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1177/1.1871512

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Pulsed field ionisation-ZEKE photoelectron spectroscopy has been applied to o-, m- and p-tolunitrile in a supersonic jet. The PFI-ZEKE photoelectron spectra of m- and p-tolunitrile show well-resolved anharmonic structures in the low-frequency region, which are assigned to bands due to internal rotational motion of the methyl group in the cation. Level energies and relative transition intensities are reproduced well by a one-dimensional rotor model with a three-fold axis potential. Potential curves for the internal rotation have been determined. For o-tolunitrile, no band due to internal rotation was found in PFI-ZEKE spectrum. It is suggested that the o-tolunitrile cation has the high barrier for internal rotation and the stable conformation that is the same as that in S-1 and S-0. The barrier height and the conformation are compared with other toluene derivatives. and the relation between the electronic character of -CN and the internal rotational motion has been discussed. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2004.09.020

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200501430

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

To generate a doughnut-shaped beam, i.e., the first order of a Bessel beam, a spiral phase plate with 8 divided etching areas is fabricated with an etching accuracy of better than 6 nm. The etching depth of each area is designed so that the phase distribution of the laser beam passing through has a phase difference of pi at a symmetric position with respect to the optical axis. Using a laser beam with a wavefront aberration of 1/10lambda, the phase distribution of the beam passing through the plate is measured by a Shack Hartman wavefront sensor. It has been found that the beam has a spiral phase change of 2pi along the optical axis. The focused beam has a circular doughnut pattern, as predicted by a theoretical calculation, and we succeeded to generate the ideal first-order of a Bessel beam. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1819555

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The picosecond time-resolved IR spectra of the 7-azaindole dimer in a carbon tetrachloride solution was measured by using picosecond time-resolved lR/UV double resonance spectroscopy. This spectroscopy selectively detects the IR transition by transient fluorescence due to an electronic transition from a vibrationally excited level. The time-evolution of the IR spectrum is a single exponential with a 19 ps lifetime, which does not correspond to fast nonstatistical decay due to the intramolecular vibrational redistribution found in a gas-phase cluster. From a comparison with the time-resolved IR spectrum of a jet-cooled dimer, this decay is assigned to vibrational cooling from the dimer to the solvent. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2004.08.041

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Science Society of Japan  

The two-point-resolution of a novel two-color far-field super-resolution fluorescence microscopy has been evaluated. This microscopy is based on a combination of two-color fluorescence dip spectroscopy and a phase modulation technique for the laser beam. The two-point-resolution of the microscopy has been evaluated by using the fluorescent beads of which the size is specified by the observation with AFM. By introducing two color lasers, the observed fluorescence image shrunk down beyond the diffraction limit. In the observation of neighboring two fluorescence beads, pronounced separation between two individual fluorescence spots has been investigated. By taking the focal depth into consideration, FWHM and profile of the fluorescence images were well reproduced. It is proved that our technique breaks the diffraction limit and the spatial resolution of the optical fluorescence microscope can be improved by 2 times higher than the diffraction limit.

DOI： 10.1380/jsssj.25.466

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Other Link： https://jlc.jst.go.jp/DN/JALC/00241790487?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

The formation of a doughnut-shaped laser beam is presented. To generate the beam, we use an optically addressed parallel-aligned nematic liquid-crystal phase spatial light modulator (PAL-SLM), and observe the shape of the focused beam. By using a compensating technique for wave aberration, the beam has a symmetric doughnut shape with a hole size of 1 mumphi on the focal plane. The experimental result shows that the generated beam can be expected to be applicable to super-resolving microscopy based on the fluorescence depletion process. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.1690767

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Nonresonant ionization detected (NID) spectroscopy has been used to record the OH-, NH-, and CH-stretching vibrational overtone spectra of o-, m-, and p-aminophenol (aminohydroxybenzene; hydroxyaniline) in the collision-free environment of a supersonic jet. The OH-, NH-, and CH-stretching fundamental vibrations of jet-cooled o- and m-aminophenol have also been studied by NID and infrared-depletion techniques. We use an anharmonic oscillator local mode model, with one oscillator for each OH, NH, and CH bond, to calculate the frequencies and intensities of the stretching transitions and facilitate the assignment of the measured vibrational spectra. In the case of m-aminophenol, the presence of two rotational isomers is clearly demonstrated in the higher vibrational overtone spectra. For o-aminophenol, we find that one rotational isomer dominates, and the possible existence of a second is discussed. Electronic structure calculations are used to determine and explain the relative energies of the various rotational isomers. Our results show that vibrational overtone spectroscopy combined with jet-cooled conditions is a powerful technique for distinguishing between rotational isomers.

DOI： 10.1021/jp037577y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

The phenylazomethine dendrimer (DPA) is associated with Rhodamine 6G in chloroform, which results in the chemical shift attributed to the aromatic protons of phenylazomethine being moved upfield in the H-1-NMR spectrum by increasing the Rhodamine 6G. The shift is saturated at the ratio of 1:1. On the basis of the NMR analysis, the association constant K of phenylazomethine with Rhodamine 6G was determined to be 1.4 x 10(4) (l/mol) in CDCl3 at 20degreesC. The association is also confirmed by UV-vis spectroscopy, in which the absorption around 450 and 527 nm changes during the addition of Rhodamine 6G. The fluorescence intensity of the 1: 1 complex of Rhodamine 6G and DPA G4 is stronger than that of the solution dissolved only in Rhodamine 6G at greater than 1 mM though it is generally known that the intermolecular interaction quenches the dye fluorescence in a concentrated solution. The association of DPA G4 with Rhodamine 6G suppresses the quenching at higher concentrations. Homogenous nano-dots were observed on mica by casting the DPA G4 complex with Rhodamine 6G, in which the height and average area were 1.5-3 nm and 1.6 x 10(3) nm(2) (the standard deviation sigma = 3.7 nm(2)), respectively. Copyright (C) 2004 John Wiley Sons, Ltd.

DOI： 10.1002/pat.378

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The hole burning spectra of phenol/ammonia (1:3 and 1:4) clusters were measured by a newly developed four-color (UV-near-IR-UV-UV) hole burning spectroscopy, which is a kind of population labeling spectroscopy. From the hole burning spectra, it was found that single species is observed in an n=3 cluster, while three isomers are observed simultaneously for n=4. A possibility was suggested that the reaction efficiency of the hydrogen transfer from the electronically excited phenol/ammonia clusters, which was measured by a comparison with the action spectra of the corresponding cluster, depends on the initial vibronic levels. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1640352

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DOI： 10.3131/jvsj.47.612

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Language：Japanese   Publisher：The Spectroscopical Society of Japan  

DOI： 10.5111/bunkou.53.2

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Other Link： https://jlc.jst.go.jp/DN/JALC/00236898891?from=CiNii

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

Pronounced separation (750 nm) between two individual fluorescence spots in a novel super-resolution microscopy based on a two-color up-conversion fluorescence depletion technique has been investigated. This microscopy has the potential to achieve a spatial resolution (&lt; 300nm) of 1/2 the diffraction limit. (C) 2003 Optical Society of America.

DOI： 10.1364/OE.11.003271

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We investigated an organic waveguide laser amplifier with grating couplers based on light-induced surface grating hologram. Optical coupling efficiency to the film was approximately 0.5%. The amplifier exhibited small-signal gain of 0.5 cm(-1). (C) 2003 Published by Elsevier B.V.

DOI： 10.1016/j.optcom.2003.09.060

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC APPLIED SPECTROSCOPY  

DOI： 10.1366/000370203769699234

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The potential energy surfaces of PhOH-(NH3)(0,1) and NH4(NH3)(1-4) have been investigated theoretically by ab initio methods. Intermolecular stretching in PhOH-NH3 assists in the radical cleavage of an OH bond occurring through a pipi*/pisigma* potential crossing. Thus, excited state hydrogen transfer (ESHT) is expected to take place by a solvent-assisted mechanism even in the larger PhOH-(NH3)(n). Because sufficient energy is obtained by ESHT from PhOH-(NH3)(n) (pipi(*)) to PhO-NH4(NH3)(n-1) (pisigma(*)) (nless than or equal to5), hydrogen relocation and/or ammonia migration in the product NH4(NH3)(n-1) can readily follow ESHT, which is responsible for observing isomer bands in the absorption spectra of the photoinduced reaction products of PhOH-(NH3)(n). (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1597492

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

By using a two-color dip-spectroscopy, we measured the fluorescence intensity from tryptophan in a water solution. The fluorescence intensity exponentially decreased as the laser intensity for the S-n &lt;-- S-1 excitation increased. The phenomenon was analyzed by a rate-equation for a three-state model. The analysis shows that tryptophan with the Sn state has a radiationless relaxation process without any process through the S-1 state, and that the S-n --&gt; S-1 internal conversion does not have a 100% yield. The branching ratio of the process is estimated to be 20%. The presented result clarifies in detail the real meaning of Kasha's rule. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(03)00481-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have demonstrated a realistic super-resolution scanning fluorescence microscope using conventional nanosecond lasers. This super-resolution microscope is based on the combination of two-color fluorescence dip spectroscopy and shape modulation to a doughnut beam. Only by introducing a doughnut erase beam, the resolution of the laser fluorescence microscope breaks the diffraction limit by two times without using any mechanical probe. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(03)00315-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

We have constructed a picosecond time-resolved IR dip spectrometer having a frequency resolution of &lt;20 cm(-1) and an instrument response time of 25 ps. In this system, the second harmonic of the idler wave from the OPA pumped at 800 nm and the remaining light from a regenerative amplifier (&lt;2.5 mJ/pulse) were differentially mixed in a KTA crystal to generate tunable high-power IR light (2750-4000 cm(-1); &gt;60 muJ). The picosecond time-resolved IR dip spectra of phenol-(H2O)(1) and carbazole-(H2O)(1) are presented to demonstrate the capability of the constructed system. The spectral changes show clear vibrational structures of not only S-0, but also S-1 in the 2800-3800 cm(-1) energy region. The system performance is also discussed.

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Language：Japanese   Publisher：The Spectroscopical Society of Japan  

DOI： 10.5111/bunkou.52.286

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DOI： 10.1246/bcsj.76.509

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Pulsed field ionization (PFI)-zero-kinetic-energy (ZEKE) photoelectron spectra are measured for 4-aminobenzonitrile (4ABN) and "NH2-donor isomer'' of 4ABN-H2O 1 : 1 complex in which the oxygen atom of water is bonded to the amino hydrogen (K. Sakota, N. Yamamoto, K. Ohashi, H. Sekiya, M. Saeki, S. Ishiuchi, M. Sakai and M. Fujii, Chem. Phys. Lett., 2001, 341, 70.). We have investigated changes in intermolecular interaction and structure of the NH2-donor isomer upon photoionization. The adiabatic ionization potentials of 4ABN and NH2-donor isomer are determined to be 66 493 and 62 843 cm(-1), respectively. The oxygen atom of water is hydrogen bonded to an amino hydrogen atom in the D-0 state of NH2 donor isomer as well as in the S-1 and S-0 states. However, the hydrogen bond is suggested to be much stronger in the D-0 state thanin the S-1 state from a substantial decrease (3650 cm(-1)) in the adiabatic potential due to the formation of a hydrogen bond. Normal mode analysis has been made for the intermolecular vibrations in the D-0 state with the aid of density functional theory calculations at the B3LYP/aug-cc-pVDZ level. The observation of a prominent progression of the intermolecular stretch mode in the PFI-ZEKE spectrum via the electronic origin of the S-1-S-0 transition is consistent with the increased hydrogen bond strength in the D-0 state.

DOI： 10.1039/b212035f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The S-1 and S-0 states of m-aminophenol have been investigated using laser induced fluorescence and dispersed fluorescence spectroscopy in a supersonic jet. The dispersed fluorescence spectra, obtained by exciting the bands at 34 109 and 34 469 cm(-1), show the same vibronic structure, which suggests the coexistence of rotational isomers in m-aminophenol. A quantum chemical calculation also supports the coexistence of rotational isomers. From the relative intensities in the spectrum and the calculated stabilization energies of isomers, the bands are assigned to the origin of the cis- and trans-isomers, respectively. The dispersed fluorescence spectra obtained by exciting the S-1 vibronic bands were analyzed by comparing with the calculated vibrational frequencies and IR and Raman spectra. From the analysis, the S-1 vibronic bands have been assigned. It was found that a one-to-one correspondence between the S-1 and S-0 vibrations is broken, and vibrational mixing due to Fermi resonance or the Duschinsky effect is suggested.

DOI： 10.1039/b309461h

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Language：Japanese   Publisher：The Surface Science Society of Japan  

A super-resolution fluorescence microscopy using two-color laser beams was proposed. The microscopy is based on the combination of two-color fluorescence dip spectroscopy and a phase modulation technique for the laser beam. By applying the proposed technique to a laser-scanning microscope, a fluorescence image of a sample can be observed with a spatial resolution overcoming the optical diffraction limit. To demonstrate validity of the microscopy, we constructed a scanning microscope system using commercial nano-second pulse lasers. An image of micro beads containing dye molecules was observed by the microscopy. We succeeded in obtaining the image with a resolution overcoming the diffraction limit in nano-meter scale region. The experimental data showed that the resolution was improved three times at least. The microscopy is expected to be an appropriate analysis method for the samples with nano-meter scale structures.

DOI： 10.1380/jsssj.24.392

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Other Link： https://jlc.jst.go.jp/DN/JALC/00230543018?from=CiNii

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The vibrational spectra of phenol/ammonia clusters (1:2-5) in S-0 and those of their photochemical reaction products, (NH3)(n-1)NH4 (n=2-5), which are generated by excited-state hydrogen transfer, have been measured by UV-IR-UV ion dip spectroscopy. The geometries, IR spectra and normal modes of phenol-(NH3)(n) (n=1-5) have been examined by ab initio molecular orbital calculations, at the second-order Moller-Plesset perturbation theory level with large basis sets. For the n=2 and 3 reaction products, similar vibrational analyses have been carried out. From the geometrical information of reactants and products, it has been suggested that the reaction products have memories of the reactant's structure, which we call "memory effect." (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1508104

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The IR-dip spectra and IR-UV hole-burning spectra of jet-cooled 4-aminobenzonitrile-water 1:1 complex have been measured to investigate the effects of the introduction of two substituents into the aromatic ring on the hydrogen-bonding interaction and stable structures of the complex. We have obtained a clear evidence for the observation of three structural isomers by comparing the experimental IR spectra with the theoretical ones. The water molecule is bonded to the NH2 site in isomer I, where the amino group can act as a proton donor and the amino hydrogen is bonded to the oxygen atom of water. Water is bonded to the CN site in isomers II and III. The structure of isomer II is very similar to benzonitrile-(H2O)(1), where the water hydrogen is bonded to the cyano nitrogen and the oxygen atom of water is bonded to the ortho hydrogen atom. The water hydrogen is linearly hydrogen-bonded to the cyano nitrogen in isomer III. The intermolecular hydrogen bond in isomer II is sigma-type, whereas that in isomer III is pi-type. The proton-donor conformer in the NH2 site and the sigma-type linear conformer in the CN site have not been observed in the aniline-(H2O)(1), and benzonitrile-(H2O)(1) complexes, respectively. The observation of three stable structures has been successfully explained by atomic charges on the constituent atoms obtained by natural population analysis. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0301-0104(02)00501-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The electronic spectra of reaction products via photoexcited phenol/ammonia clusters (1:2-5) have been measured by UV-near-IR-UV ion dip spectroscopy. Compared with the electronic spectra of hydrogenated ammonia cluster radicals the reaction products have been proven to be (NH3)(n-1)NH4 (n=2-5), which are generated by excited-state hydrogen transfer in PhOH-(NH3)(n). By comparing the experimental results with ab initio molecular orbital calculations at multireference single and double excitation configuration interaction level, it has been found that the reaction products (NH3)(n-1)NH4 (for n=3 and 4), contain some isomers. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1508103

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG  

The picosecond time-resolved IR spectrum of the 7-azaindole dimer has been measured by picosecond time-resolved nonresonant ionization detected IR spectroscopy. This new time-resolved technique was developed by combining nonresonant ionization detected IR (NID-IR) spectroscopy with tunable picosecond IR and UV lasers. The time-resolved NID-IR spectrum from 2 600 cm(-1) to 3 800 cm(-1) shows a drastic change from 1.5 ps to 11 ps time evolution. A mode-specific vibrational redistribution has been suggested.

DOI： 10.1140/epjd/e2002-00162-7

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Language：English   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/jp014309w

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have recorded the CH-, OH-, and OD-stretching fundamental and overtone spectra of catechol (1,2-dihydroxybenzene, pyrocatechol) and selectively deuterated catechol. Conventional and intracavity photo-acoustic spectroscopy were used to record room temperature spectra of catechol in solution and in the vapor phase, whereas nonresonant ionization detected spectroscopy was used to study catechol in a supersonic jet. The spectra can be explained in terms of a local mode model with one oscillator for each of the nonequivalent CH, OH, or OD bonds. Intensities of the CH-, OH-, and OD-stretching transitions were calculated with an anharmonic oscillator local mode model and ab initio determined dipole moment functions. Our simple calculations are in good agreement with the observed intensities. Line widths in the jet-cooled spectra are discussed in terms of intramolecular vibrational redistribution. The spectroscopic and theoretical results are in agreement with a relatively weak intramolecular hydrogen bond.

DOI： 10.1021/jp0124847

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Pulsed field ionization zero kinetic energy (PFI-ZEKE) photoelectron spectroscopy has been applied to study the cationic ground states of the rotational isomers of m-fluorophenol and its hydrogen-bonded clusters with H2O and D2O. The cis- and trans- monomer isomers are assigned by comparing the observed ionization potentials with values obtained from ab initio calculations (HF/6-31G*). Both monomers display very similar vibrational frequencies, indicating that the geometric structures of the two cations are similar. In contrast, the cis- and trans- aqueous clusters display distinctive intermolecular vibrational frequencies (e.g. the intermolecular stretching vibrations appear at 239 and 228 cm(-1) in the cis- and trans- isomers respectively). The origin of the different intermolecular interactions in the isomeric clusters is discussed with reference to the ab initio calculations.

DOI： 10.1039/b201107g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The structures of 1-naphthol/alcohol clusters, 1-NpOH(ROH)(n) (n = 1-3; ROH = MeOH, EtOH, and t-BuOH), have been investigated by resonant two-photon ionization (R2PI) spectroscopy and ion-detected IR dip spectroscopy. On the basis of the calculated spectra obtained by ab initio MO calculations, the spectra of 1-NpOH(MeOH)(n) was analyzed. The analysis elucidated that 1-NpOH(MeOH)(2,3) was a ring structure. From a similarity of the spectral pattern, the structures of 1-NpOH(EtOH)(n) and 1-NpOH(t-BuOH)(n) were also determined to be a ring conformation. From a frequency shift of the hydrogen-bonded OH stretching vibration, the hydrogen bonding is weakened by a steric hindrance due to an alkyl group of ROH. The difference in the solvation mechanism between 1-NpOH(MeOH)(n) and 1-NpOH(H2O)(n) is discussed.

DOI： 10.1021/jp0112469

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The IR spectrum of 7-azaindole monomer, 7-azaindole reactive and nonreactive dimers, and (7-azaindole)(H2O)(n) (n = 1-3) clusters in a supersonic jet from 2600 to 3800 cm(-1) have been measured using IR dip spectroscopy. The vibrational transitions in the ground state were clearly observed and were assigned to the CH and NH stretching vibrations of 7-azaindole and the OH stretching vibrations of water molecules in the clusters. The observed IR spectra of 7-azaindole monomer and (7-azaindole)(H2O)(n) (n = 1-3) clusters were compared to theoretical ones obtained by ab initio MO calculations. From a comparison, it is concluded that (7-azaindole)(H2O)(n) (n = 1-3) clusters have a ring structure due to a cyclic hydrogen-bond network. This conclusion is consistent with an analysis based on high-resolution spectroscopy. Similarly, the IR dip spectrum suggests that the 7-azaindole reactive dimer has a cyclic hydrogen-bond network, forming a symmetric planar structure. It is strongly suggested from the IR spectrum and the ab initio calculations that the nonreactive dimer contains a water molecule between 7-azaindole molecules.

DOI： 10.1021/jp011245g

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Language：Japanese   Publisher：The Laser Society of Japan  

DOI： 10.2184/lsj.29.Supplement_155

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DOI： 10.1021/jp012218t

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DOI： 10.1016/S0009-2614(01)00463-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Pulsed field ionization zero kinetic energy (PFI-ZEKE) photoelectron spectra were measured for jet-cooled o-, m-, and p-methylanisoles for the first time. The low-frequency bands observed at around the origin band in the spectra were assigned to the methyl internal rotational bands of the cations. The potential curves and the Franck-Condon factors for the methyl internal rotational motion were calculated by the one-dimensional free-rotor approximation. The potential barrier height was found to change drastically on ionization, suggesting that the electronic structure should mainly affect the potential barrier of the methyl internal rotation.

DOI： 10.1039/B105719G

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DOI： 10.1016/S0009-2614(01)01017-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Pulsed field ionization-zero kinetic energy photoelectron spectroscopy has been applied to 1,2,4,5-tetrafluorobenzene in a supersonic jet. The spectrum measured by selecting a specific vibronic level of the butterfly vibrational mode in S-1 by the first laser shows a well-resolved vibrational structure of the cation. A long progression has been assigned to the out-of-plane butterfly vibrational mode 11 with an even quantum number in the cation. From the harmonisity and Franck-Condon factor, it has been concluded that the molecular structure of the tetrafluorobenzene cation is hat, though that in S-1 is non-planer along the butterfly vibrational mode. The geometrical change upon ionization is discussed in terms of the electronic structure. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0368-2048(00)00217-6

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