Depolarized Rayleigh and Raman scattering from N₂

Abstract

In this paper depolarized Rayleigh and Raman spectra from N₂ in the density range ρ_r = 0·007 to 2·43 (ρ_r = ρ/ρ_c) are reported. The main goal of our comparison of the two types of spectra is to demonstrate that rotation-vibration spectra over this range of fluid densities can be influenced by a change of the molecular moment of inertia on vibrational excitation. The effect is different from vibrational relaxation, self and distinct rotation, interaction induced, and other contributions usually considered as broadening or narrowing mechanisms of condensed phase Rayleigh and Raman bands. Although the mechanism is well established for gas phase rotation-vibration IR, Raman and electronic spectra [14], to the best of our knowledge it has been neglected so far in the context of rotation-vibration spectra at high densities. For comparison of experiments with classical molecular dynamics simulations, classical spectra are required. It is shown that in order to obtain classical spectra from rotation-vibration spectra, apart from the well known detailed balance correction, a frequency rescaling may be necessary.