The liquid–glass transition in LiCl/H2O: Impulsive stimulated light scattering experiments and mode-coupling analysis

Abstract

Impulsive stimulated light scattering (ISS) experiments have been conducted on aqueous LiCl solutions to characterize the structural relaxation dynamics at temperatures above, near and below the glass transition temperature T_g. The data provide acoustic velocities, attenuation and thermal diffusion rates over wide ranges of temperature and wave vector. At temperatures in the glass transition region, the dynamics of thermal expansion and subsequent contraction (not due to thermal diffusion) are observed as well. The acoustic information from ISS as well as from earlier Brillouin scattering results is used to determine the frequency‐dependent elastic modulus in the MHz–GHz range. Analysis in terms of an empirical (stretched exponential) relaxation function is carried out and shown to be inadequate. The main analysis is inspired by predictions of mode‐coupling theory concerning susceptibility spectra. Simple scaling for the α‐peak and identical power law dependencies on frequency for both electrical and mechanical moduli, as predicted by theory, were confirmed.