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/spl deg/ 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/sub m/(/spl sim/1.5 GPa). The pressure dependence of the relaxation time was obtained. For ethanol the temperature dependence is compared with the /spl alpha/-relaxation time determined by dielectric measurements. It is found that the relaxation time relates to the LA-modes are much faster than those of /spl alpha/-relaxation.
展开▼
