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Titolo:
CH-stretching overtone spectra of a fast rotating methyl group. I. TolueneC6D5CH3
Autore:
Cavagnat, D; Lespade, L;
Indirizzi:
Univ Bordeaux 1, Lab Physicochim Mol, CNRS, UMR 5803, F-33405 Talence, France Univ Bordeaux 1 Talence France F-33405 UMR 5803, F-33405 Talence, France
Titolo Testata:
JOURNAL OF CHEMICAL PHYSICS
fascicolo: 14, volume: 114, anno: 2001,
pagine: 6030 - 6040
SICI:
0021-9606(20010408)114:14<6030:COSOAF>2.0.ZU;2-3
Fonte:
ISI
Lingua:
ENG
Soggetto:
INTRAMOLECULAR VIBRATIONAL REDISTRIBUTION; INTERNAL DYNAMICS CONTRIBUTIONS; FREE ASYMMETRIC ROTORS; EXCITED METHANOL; P-FLUOROTOLUENE; ENERGY-TRANSFER; LOCAL MODES; NITROMETHANE NO2CHD2; CLASSICAL SYSTEM; FERMI RESONANCES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
63
Recensione:
Indirizzi per estratti:
Indirizzo: Cavagnat, D Univ Bordeaux 1, Lab Physicochim Mol, CNRS, UMR 5803, 351 Cours Liberat, F-33405 Talence, France Univ Bordeaux 1 351 Cours Liberat Talence France F-33405 ance
Citazione:
D. Cavagnat e L. Lespade, "CH-stretching overtone spectra of a fast rotating methyl group. I. TolueneC6D5CH3", J CHEM PHYS, 114(14), 2001, pp. 6030-6040

Abstract

The CH-stretching overtone spectra of the methyl group in gaseous toluene C6D5CH3 are recorded with conventional Fourier transform near infrared spectroscopy in the Deltav(CH)=1-4 regions and by intracavity laser photoacoustic spectroscopy in the Deltav(CH)=5 and 6 regions. All spectra exhibit a complex structure. They are analyzed with a theoretical model which takes into account, within the adiabatic approximation, the coupling of the anharmonic CH stretch vibrations, described by Morse potentials, with the quasifreeinternal rotation of the methyl group and with isoenergetic combination states involving the six angle deformation modes of the methyl group. Using uniquely determined canonical potential-energy and kinetic-energy matrices allows us to solve the problem of indeterminacy caused by the description ofmolecular vibrations in such redundant coordinates. A set of Fermi resonance parameters and their variation with the internal rotation coordinate aredetermined from the fitting of the Deltav(CH)=1-6 overtone spectra. At Deltav=1 and 2, the vibrational energy is expressed in a normal mode basis. Fermi resonance phenomena involving mainly the HCH bending modes lead to strong intramolecular vibrational energy redistribution. At this energy, a Coriolis coupling through internal rotation, which gives rise to a characteristic asymmetric top vibration-rotation profile, further perturbs the vibrational modes perpendicular to the rotation axis. From the second overtone (Deltav=3), the vibrational energy is described in a local mode basis and perturbations due to Fermi resonance vanish progressively up to Deltav=5. At Deltav=6, a strong spectral perturbation is again observed. But, the efficientFermi resonance phenomena are now essentially related to combination states involving HCH and HCC bending combination modes. This simple calculation successfully describes the relative intensity and frequency of each peak within a given overtone. (C) 2001 American Institute of Physics.

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Documento generato il 13/08/20 alle ore 14:33:59