Raman Scattering: Orientational Motions in Liquids

Abstract

A systematic study of reorientational motions by Raman scattering is undertaken for 10 liquids. The theory of orientational broadening of Raman lines is presented with emphasis on the use of symmetry of molecular vibrations to obtain information of reorientational motions about different axes. The rotational diffusion tensor of benzene was obtained and found to be approximately isotropic. The time for reorientation of the major molecular axis was measured for nine liquids and the mechanism for reorientation for these liquids discussed. Liquids are classified according to whether reorientation is determined by structural dynamics or collisional motions. Finally it was possible to obtain the time between collisions for liquids in which reorientation is collision limited and occurs in small angular steps.