Light scattering studies of orientational fluctuations of CS₂

We have measured the depolarized Rayleigh relaxation time of CS₂ as a function of temperature and concentration in an optically isotropic solvent CCl₄. The concentration dependence of the relaxation times indicates the importance of orientational pair correlation in CS₂. The orientational pair correlation factor is found to depend on concentration at high CS₂ concentration, as well as viscosity and temperature, in contrast to what is observed in other small molecules. The single particle reorientation times were obtained by extrapolating from the depolarized Rayleigh relaxation times to infinite dilution. These were compared with the predictions of the hydrodynamic slip and stick models for rotational diffusion. As is usual for small molecules, the slip boundary condition better approximates the experimental results. The single particle reorientation times were also compared with the correlation times obtained by ¹³C NMR and ³³S NQR measurements. They were found to be in good agreement.