Depolarized Rayleigh scattering

Abstract

Depolarized Rayleigh experiments on CO₂ at 40°C in the density range 0·1_ρc to 2·35_ρc (ρc=critical density) are reported. From the spectra orientational correlation and memory functions are calculated, which are compared with corresponding correlation functions of the J-diffusion model. The density dependence of the collision parameter β of the J-diffusion model and of the mean square torque factor <N ²>/4(kT)² are given. It is found that the J-diffusion model gives an almost perfect description of the reorientational dynamics as long as the density is less than 0·8 times ρc. At densities larger than about 1·5_ρc the J-diffusion model fails to account for the short time behaviour of the correlation functions, which indicate that a highly damped librational motion becomes an essential part of the molecular reorientation.