Angular and temperature dependence of depolarized and polarized Rayleigh-Brillouin spectra of a supercooled liquid: o-terphenyl

Abstract

The angular and temperature dependence of polarized and depolarized Rayleigh-Brillouin spectra of o-terphenyl have been studied with a Fabry-Perot interferometer. In the VV spectra, considerable dispersion is observed, manifested by a linewidth maximum and by a gradual change in the frequency versus temperature plot. These effects are interpreted as due to structural relaxation. In the VH spectrum, a central shear dip is observed at high temperature. As the liquid is supercooled, shifted peaks due to oscillatory shear waves also appear. The frequency of the shear peaks decreases with increasing temperature and becomes vanishingly small at the temperature at which the Brillouin-linewidth of the longitudinal acoustic wave is maximum. Furthermore, the shear wave frequency is found to be proportional to q and the linewidth as well as the rotation-translation coupling parameter are proportional to q ².