Relaxation processes in liquid and supercooled toluene by light scattering experiments

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Abstract
We report detailed light scattering experiments in toluene comprising measurements of shifts and linewidths of polarized (VV) and depolarized (VH) spectra in the temperature range from 30°C to the glass transition T g = - 156°C. The values of the longitudinal sound velocity and attenuation are analysed in association with the existing ultrasonic data. We find that both types of measurement support the prevalence of a vibrational relaxation process at high temperatures and a viscous one (structural+shear viscosity) at low temperatures. Viscous processes are analysed in the framework of current viscoelastic models. Transverse light scattering data do not agree with the corresponding quantities usually found in ultrasonic shear wave experiments. Although longitudinal properties look similar to those obtained in ultrasonic experiments, we find unusual features in the compressional component.