From light-scattering measurements to polarizability derivatives in vibrational Raman spectroscopy: The 2 nu(5) overtone of SF6

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TitreFrom light-scattering measurements to polarizability derivatives in vibrational Raman spectroscopy: The 2 nu(5) overtone of SF6
Type de publicationArticle de revue
AuteurKremer, David , Rachet, Florent , Chrysos, Michel
EditeurAmerican Institute of Physics
TypeArticle scientifique dans une revue à comité de lecture
Année2013
LangueAnglais
Date05/2013
Numéro17
Volume138
Titre de la revueJournal of Chemical Physics
ISSN0021-9606
Mots-clés(sf6)-s-32, anharmonicity, combination band, intensities, mean molecular polarizability, octahedral molecules, region, resolution ftir spectrum, sulfur-hexafluoride, temperature-dependence
Résumé en anglais

The room-temperature isotropic spectrum of SF6 was recorded at the frequency of the 2 nu(5) overtone by running high-sensitivity incoherent Raman experiments for two independent polarizations of the incident beam and for gas densities varying from 2 to 27 amagat. Weak yet observable pressure effects were found. A transparent analysis of the Raman cross-section problem along with the first-ever prediction of the value of the mean polarizability second derivative partial derivative(2)(alpha) over bar/partial derivative q(5)(2) are made and the hitherto underestimated role of the hot bands of SF6 is brought to the wider public. The emergence of an analytic hotband factor is shown whose magnitude is dramatically increased with the order of the overtone and the gas temperature and all the more so upon considering low-frequency molecular vibrations. Our formulas, which in the harmonic approximation are exact, are still applicable to real situations provided certain conditions are fulfilled. For nondegenerated modes, generalization to higher order overtones is made, an issue addressing the much challenging problem of the IR-allowed second overtone bands. The content of this paper is also an invitation towards ab initio derivative-calculations for sulfur hexafluoride, especially given the today's needs in interpreting spectra of significance for greenhouse atmospheric issues.

URL de la noticehttp://okina.univ-angers.fr/publications/ua3194
DOI10.1063/1.4803160