Depolarized Rayleigh scattering

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Abstract
Depolarized Rayleigh experiments on CO2 at 40°C in the density range 0·1ρc to 2·35ρc (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 1·5ρc 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.