Depolarized Rayleigh-Brillouin scattering of shear waves and molecular reorientation in a viscoelastic liquid

Abstract

A microscopic theory of depolarized Rayleigh-Brillouin spectra for viscoelastic liquids is developed. The theory takes into account the oscillation as well as relaxation of shear modes which couple to the polarizability density in a rotationally isotropic system. The experimental results of liquid and supercooled liquid salol have been analysed using the present theoretical result. Not only the detailed lineshape of the spectra at all temperatures can be interpreted consistently using one equation, the temperature dependence of the intensity ratio of the central component to the shifted shear mode side bands can also be accounted for. It is expected that this theory is applicable to the interpretation of depolarized Rayleigh spectra of supercooled liquids or glasses consisting of optically anisotropic molecules.