Koji Kaya

Resonance Raman effect of I−3 ion by ultraviolet laser excitation

Abstract The resonance Raman effect of the I −1 3 ion was observed by the use of an ultraviolet nitrogen pulsed laser. It was found that the totally symmetric stretching vibration of 112 cm −1 undergoes selective enhancement and the overtones up to the seventh order of this vibration could be observed. The result agrees well with the prediction by Nafie et al.

Multiphoton ionization spectra of benzene, fluorobenzene, and chlorobenzene resonant with S0–S1 transitions by use of nozzle beam method

Multiphoton ionization technique combined with nozzle beam method was applied to the observation of two‐photon absorption spectra of benzene, fluorobenzene, and chlorobenzene in S0–S1 valence shell excitations. Strong two‐photon activity of ν14 (b2u or b2) vibration throughout these molecules was established. Details of the multiphoton ionization spectrum of chlorobenzene which was observed for the first time will be given. It was concluded that the two‐photon resonant four‐photon ionization spectra obtained in the present work reflect correct two‐photon absorption cross sections. The vibrational temperature of a lower frequency vibration was found to decrease preferentially in an expanded low temperature nozzle beam.

The multiphoton ionization spectrum of toluene in a supersonic free jet: internal rotation of the methyl group

Abstract The S 1 ← S o electronic transitions of toluene involving also some internal rotational levels were observed for the first time in the multiphoton ionization spectrum in a supersonic jet. A large population in several low-lying internal rotational levels and a strong coupling between electronic motion and the internal rotation are suggested.

Electronic absorption spectra of biphenyl as studied by multiphoton ionization–supersonic beam technique

The vibrational structure of biphenyl is studied by observing the multiphoton ionization spectra due to radiation from a dye (coumarin 540) laser.(AIP)

Vibronic coupling of pyridine in the nπ* excited state

The electronic absorption spectra and Raman spectra of pyridine and pyridine‐d5 were measured. The vibrational analysis of the nπ* absorption spectrum and the preresonance Raman effect showed that the CH out‐of‐plane bending vibration ν10a(a2) (of the ground and excited‐state frequencies 886 and 331 cm−1 for pyridine) is responsible for the vibronic coupling between the lowest nπ* state and the second lowest ππ* state.

Resonance Raman scattering and the Jahn-Teller effect of oxocarbon ions

Abstract The Raman spectra of C 6 O 6 2− have been measured under rigorous resonance condition and the excitation profiles of several Raman lines were obtained in the whole region of the absorption band. The characteristic feature of the excitation profiles indicates the occurrence of the Jahn-Teller effect in the lowest allowed degenerate excited state. Using MO and normal coordinates, the Jahn-Teller coupling strengths for three oxocarbon ions, i.e. C 4 O 4 2− , C 5 O 5 2− and C 6 O 6 2− were calculated by the perturbation period. The theoretical results were in fair agreement with the experimental results. The deformations of the ions in the lowest allowed excited states resulting from the Jahn-Teller coupling were predicted.

Vibronic coupling and Raman intensities of pyrazine

Abstract The fluorescence spectrum of pyrazine vapour and the Raman spectra of liquid pyrazine excited at various wavelengths were observed. The appearance of the long progression of the hydrogen bending vibration ν 5 (b 2g ) in the fluorescence spectrum and a remarkable preresonance effect of the Raman line of the same vibration confirm the theoretical prediction given by Albrecht.

Raman spectra and Jahn-teller effects of C4O2-4 and C5O2-5 ions

Abstract The Raman spectra of highly symmetrical ions C 4 O 2- 4 (D 4h ) and C 5 O 2- 5 (D 5h ) have been measured at various excitation wavelengths. The spectra are characterized by strong Raman intensities of some non-totally symmetric vibrations at off-resonant condition and their remarkable intensity enhancement at near and rigorous resonant conditions. The characteristic features of the Raman spectra are closely related with the Jahn-Teller effects of the lowest degenerate π,π* electronic excited states of these ions.

Resonance Raman spectra of the halogenomethanes excited by ultraviolet nitrogen pulsed laser

Abstract The Raman spectra of liquid CCl 4 , CHCl 3 , CH 2 Cl 2 , CHBr 3 and CH 2 Br 2 excited with 6328 A He-Ne laser and 3371 A nitrogen pulsed laser were measured. A remarkable resonance effect was found for the Raman lines of the antisymmetric C-X stretching vibrations. The results obtained were discussed in relation to the excited electronic states.

Resonance raman profile of the Jahn-Teller coupled vibrations in the croconate ion

Abstract The resonance Raman profile of the Jahn-Teller coupled vibrations has been investigated in croconate ion, both experimentally and theoretically. A good qualitative agreement between theory and experiment is found for two non-totally symmetric vibrations which are taken into account in the theoretical calculation.