Yoshiteru Matsumoto

Characterizations of the hydrogen-bond structures of 2-naphthol-(H2O)n (n=0–3 and 5) clusters by infrared-ultraviolet double-resonance spectroscopy

OH stretching vibrations of 2-naphthol-(H2O)n (n=0–3 and 5) hydrogen-bonded clusters in the S0 state have been observed by infrared-ultraviolet (IR-UV) double-resonance spectroscopy. In bare 2-naphthol, cis- and trans-isomers were identified by the comparison of the observed OH frequencies with those obtained by ab initio calculations with the HF/6-31G basis set. The OH stretching vibrations (νOH) of hydrogen-bonded 2-naphthol-(H2O)n show characteristic shifts depending on the cluster size. They are classified into hydrogen-bonded νOH, and νOH free from the hydrogen bond. The cluster structures were also examined by comparing the observed IR spectra with simulated ones. It was found that the clusters with n=2 and 3 form ring structures, while the cluster with n=5 exhibits an ice (I) structure.

OH stretching vibrations and hydrogen-bonded structures of 7-hydroxyquinoline-(H2O)1–3 investigated by IR–UV double-resonance spectroscopy

Abstract Hydrogen(H)-bonded structures of 7-hydroxyquinoline-(H 2 O) n clusters were investigated based on the analysis of the infrared spectra of the OH stretching vibrations in combination with ab initio calculations. For 7-hydroxyquinoline-(H 2 O) 1 , two isomers due to different H-bonding sites were found to coexist; in one of them 7-hydroxyquinoline acts as a proton donor, and in the other the OH group of water is H-bonded to the nitrogen site of 7-hydroxyquinoline. For 7-hydroxyquinoline-(H 2 O) 2–3 , the structures were determined to be bridge forms, in which a linear-form water cluster is H-bonded to the OH hydrogen and to the nitrogen of 7-hydroxyquinoline.

Femtosecond photoelectron imaging of pyridazine: S1 lifetime and (3s(n−1),3p(n−1)) Rydberg state energetics

The first real-time study on pyridazine in the S1(n,π*) state is presented. The S1 state is found to dephase with a time constant of 323±17 ps at its origin, and the electronic dephasing mechanism is attributed to the S1–S0 internal conversion. The S1 lifetime is found to decrease rather sharply as the internal energy increases. The 3s (n−1) and 3p (n−1) Rydberg states of pyridazine are clearly identified in angle- and energy-resolved photoelectron images obtained in the (1+2′) photoionization scheme, providing their respective term values of 5.68±0.03 and 6.28±0.04 eV.

One- and two-color photoelectron imaging of the CO molecule via the B 1Σ+ state

This paper is concerned with photoelectron imaging following one-color (2+1) and two-color (2+1′) resonance enhanced multiphoton ionization in the CO molecule. After the two-photon absorption step B 1Σ+ (v′=0)←←X 1Σ+ (v″=0) or B 1Σ+ (v′=1)←←X 1Σ+ (v″=0), the subsequent one-photon ionization X 2Σ+(v+)←B 1Σ+ (v′=0,1) shows deviations from the expected Δv=0 Franck–Condon propensity rule. The results are in good agreement with a previous study using time-of-flight photoelectron spectroscopy [Sha et al., J. Chem. Phys. 99, 4334 (1993)]. The experimental photoelectron kinetic energy spectra and their angular distributions are analyzed, and the essential role played by “superexcited” Rydberg states with an A 2Π ion core in this process is examined. Moreover, photoelectron imaging methods appear to be useful in extracting information about superexcited states.

Reaction dynamics of Al + O2 → AlO + O studied by a crossed-beam velocity map imaging technique: Vib-rotational state selected angular-kinetic energy distribution

Oxidation reaction of a gas-phase aluminum atom by a molecular oxygen was studied by a crossed-beam condition at 12.4 kJ/mol of collision energy. A (1+1) resonance-enhanced multiphoton ionization (REMPI) via the D(2)Σ(+)-X(2)Σ(+) transition of AlO was applied to ionize the product. The REMPI spectrum was analyzed to determine rotational state distributions for v = 0-2 of AlO. For several vib-rotational states of AlO, state selected angular and kinetic energy distributions were determined by a time-sliced ion imaging technique for the first time. Kinetic energy distributions were well represented by that taken into account initial energy spreads of collision energy and the population of the spin-orbit levels of the counter product O((3)P(J)) determined previously. All angular distributions showed forward and backward peaks, and the forward peaks were more pronounced than the backward one for the states of low internal energy. The backward peak intensity became comparable to the forward one for the states of high internal energy. These results and the rotational state distributions suggested that the reaction proceeds via an intermediate which has a lifetime comparable to or shorter than its rotational period.

Identification of crystalline structures in jet-cooled acetylene large clusters studied by two-dimensional correlation infrared spectroscopy

We investigated the crystalline structures of jet-cooled acetylene (C2H2) large clusters by laser spectroscopy and chemometrics. The CH stretching vibrations of the C2H2 large clusters were observed by infrared (IR) cavity ringdown spectroscopy. The IR spectra of C2H2 clusters were measured under the conditions of various concentrations of C2H2/He mixture gas for supersonic jets. Upon increasing the gas concentration from 1% to 10%, we observed a rapid intensity enhancement for a band in the IR spectra. The strong dependence of the intensity on the gas concentration indicates that the band was assigned to CH stretching vibrations of the large clusters. An analysis of the IR spectra by two-dimensional correlation spectroscopy revealed that the IR absorption due to the C2H2 large cluster is decomposed into two CH stretching vibrations. The vibrational frequencies of the two bands are almost equivalent to the IR absorption of the pure- and poly-crystalline orthorhombic structures in the aerosol particles. The characteristic temperature behavior of the IR spectra implies the existence of the other large cluster, which is discussed in terms of the phase transition of a bulk crystal.