Structural relaxation and mode coupling in a non-glassforming liquid: Depolarized light scattering in benzene

Abstract

We have measured depolarized light scattering in liquid benzene over the whole accessible temperature range and over four decades in frequency. Between 40 and 180GHz we find a susceptibility peak due to structural relaxation. This peak shows stretching and time-temperature scaling as known from alpha; relaxation in glass-forming materials. A simple mode-coupling model provides consistent fits of the entire data set. These qualitative and quantitative results show that structural relaxation in ordinary liquids and α relaxation in glass-forming materials are one and the same physical process. Thus, a deeper understanding of equilibrium liquids is reached by applying concepts that were originally developed in the context of glass-transition research.