Molecular reorientation in liquids by Rayleigh scattering: Pressure dependence of rotational correlation functions

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Abstract
Results of high pressure study of the depolarized Rayleigh scattering in acetone, benzene, and methyl iodide are presented. The density dependences of the angular velocity and angular position correlation functions are determined. The angular velocity correlation function of each liquid shows a negative overshoot. In addition, benzene at all pressures and methyl iodide at high pressures exhibit additional oscillations in the angular velocity correlation function. The details of the correlation functions are discussed in terms of ''collision interrupted'' models such as the well known J‐diffusion model. It is concluded that a more general description than J diffusion capable of allowing incomplete loss of momentum upon collision is needed. The results are compared to studies of reorientation by means of NMR. Finally, the relation between shear viscosity and reorientation in these liquids is discussed.