Excitation of localized oscillations: The high vibrational overtone spectrum of SF6

Publisher Website
Google Scholar
Abstract
An optical parametric oscillator and photoacoustic detection are used to obtain the vibrational overtone spectrum of 193 K SF6 (g) in the range 2800–4200 cm−1. Ten quaternary combinations and one band of five vibrational quanta 2ν23ν3 are identified. Four bands ν12ν2ν3, ν23ν3, ν13ν3, and 2ν23ν3 exhibit similar absorption contours to 3ν3. Combination bands of the stretching modes (ν1,ν2,ν3) are the dominant features in the spectrum. For these bands, the absorption is attributable to the lowest energy member of the several allowed (F1u) components of each band. The vibrational motion is localized along a single Cartesian axis of the molecule, because of the strong kinetic coupling of vibrations of opposing S–F bonds. The global nature of the SF6 overtone spectrum is reproduced by a model that assumes radiation selectively excites levels according to their degree of local character.