Vibrational phase and energy relaxation in the broadening of Raman spectral lines in dense media

Abstract

An explicit quantum-mechanical expression for the linewidth of the isotropic Raman band for a dilute solution of Raman-active molecules in an “inert” solvent is summarily derived. Line broadening in such a system arises from two mechanisms: pure vibrational dephasing, which is due to nearly elastic scattering processes within the solvent leaving the vibrational state of the active molecule essentially unchanged; vibrational energy relaxation, which involves inelastic transitions, the vibrational state of the active molecule changing. A specific model for diatomic molecules in rare-gas matrices has been developed and applied to the case of N 2 in Ar. The agreement with experiment is not bad.