Molecular dynamics studies of orientational and collision-induced light scattering in molecular fluids

Abstract

Molecular dynamics calculations of the Rayleigh and Raman light scattering properties of atom–atom Lennard-Jones fluids (’’N2’’, ’’O2’’, ’’Cl2’’, and ’’CO2’’) have been made, including collision-induced (CI) effects to lowest order in the dipole-induced dipole approximation. CI effects are shown to result in deviations from the Lorentz–Lorenz (Claus–Mosotti) relation, changes in the spectral moments of both Rayleigh an Raman bands and in their depolarization ratios. Where possible, the predicted magnitudes are compared with experiment. Calculated CI influences on the effective molecular polarizability are compared with theoretical estimates based on the superposition approximation. The importance of isotropic CI light scattering in molecular fluids is indicated. Finally, we discuss the separability of orientational and CI contributions to depolarized spectra.