Brillouin scattering of simple molecular liquids at high pressure

The pressure dependences of the longitudinal acoustic mode (LA) of methanol, ethanol and toluene were measured by Brillouin scattering in the backward scattering geometry with the scattering angle 120° up to 3 GPa. Except methanol, toluene and ethanol freeze at 1.7 and 2.7 GPa, respectively. The linewidth of Brillouin components of these liquids show attenuation maxima at pressure P_m(~1.5 GPa). The pressure dependence of the relaxation time was obtained. For ethanol the temperature dependence is compared with the α-relaxation time determined by dielectric measurements. It is found that the relaxation time relates to the LA-modes are much faster than those of α-relaxation