RAMAN-SPECTROSCOPIC STUDY OF THE SINGLE-PARTICLE DYNAMICS OF CS2 IN LIQUID BINARY-MIXTURES WITH CCL4

Using the polarized and depolarized scattering geometry we studied the concentration dependence of the isotropic and anisotropic Raman spect ra of the symmetric stretching mode nu1 Of CS2 in liquid mixtures with CCl4 at 25-degrees-C. The vibrational relaxation of the nu1 mode can be characterized as a pure dephasing process in the fast modulation re gime over the whole concentration range. We discuss orientational corr elation functions and correlation times tau(or) indicating a diffusion al tumbling motion of the symmetry axis. Testing the most relevant hyd rodynamic models we found a strong deviation from linearity of tau(or) against eta/T. The orientational diffusion behaviour may be character ized by the transition from the hydrodynamic to the non-hydrodynamic o r the so-called sub slip boundary condition.