Interaction-induced contributions to Rayleigh and allowed Raman bands

Molecular dynamics simulations of a model of CS2 have been analysed to calculate the shapes and intensities of the Rayleigh and allowed Raman bands of the liquid. The calculations are performed using the first order dipole induced dipole mechanism (DID). There is a clear time scale separation between the collision induced and reorientational components of the spectrum which becomes more marked at lower temperatures. The projection factors which determine the effective polarizabilities are large for CS2 at first order DID and second order DID terms calculated for the Raman polarizabilities are also substantial. An empirical renormalization scheme to incorporate higher order DID effects for the Raman intensities is described. A simple model which neglects orientational correlations and orientational translational correlations provides a semi quantitative prediction of the collision induced intensities.