Effects of intermolecular interactions on depolarized Rayleigh scattering intensities of fluids of linear molecules

Abstract

We report the results of a study of interaction-induced (I-I) effects on the depolarized Rayleigh scattering (DRS) intensity of fluids of linear molecules. Monte Carlo and molecular dynamics computer simulation, as well as analytical theory, are used to calculate DRS intensities of model fluids designed to represent N₂, CO₂, and O₂ at a set of densities and temperatures. The I-I, or ‘collision-induced’, polarizability is evaluated using the first order dipole-induced dipole model. The contributions to the intensity from intermolecular pair correlations, cross-correlations between molecular and I-I polarizability, and collision-induced polarizability autocorrelation, are studied. With the aid of the analytical theory, the computer simulation results are analysed in terms of the density dependence of the correction factors F _cc and F _mc, measuring the contributions of triplet and higher intermolecular correlations to collision-induced and cross terms in the intensity. We find that molecular shape, polarizability, and temperature of the fluid can have important effects on the density dependence of the DRS intensity. We also find that the polarizability anisotropy contribution to the I-I polarizability substantially affects the DRS intensity at high densities.