Raman spectroscopic study of the single particle dynamics of CS₂ in liquid binary mixtures with CCl₄

Abstract

Using the polarized and depolarized scattering geometry we studied the concentration dependence of the isotropic and anisotropic Raman spectra of the symmetric stretching mode v ₁ of CS₂ in liquid mixtures with CCl₄ at 25°C. The vibrational relaxation of the v ₁ mode can be characterized as a pure dephasing process in the fast modulation regime over the whole concentration range. We discuss orientational correlation functions and correlation times τ_or indicating a diffusional tumbling motion of the symmetry axis. Testing the most relevant hydrodynamic models we found a strong deviation from linearity of τ_or against η/T. The orientational diffusion behaviour may be characterized by the transition from the hydrodynamic to the non-hydrodynamic or the so-called sub slip boundary condition.