Relaxation in simple liquids by polarized light scattering

Abstract

The polarized spectra of liquid CCl₄, CHl₃, C₆H₅F and C₆H₅Cl were obtained by interferometric light scattering analysis over a temperature range of ∼ 80°C for each substance.

The data obtained from the Brillouin lines show a hypersound dispersion which could be fitted to a relaxation equation with a single relaxation time. We thus could obtain values for the relaxation time τ and for the relaxation strength R as functions of the temperature.

The values of R and the temperature dependence of this quantity have yielded an insight into the nature of the observed relaxation processes which appear to correspond to the T-V energy transfer involving the lowest or, occasionally, the second lowest vibrational level ν_init.

The temperature dependence of τ enables us, within the frame of the Schwarz–Slawsky–Herzfeld–Tanczos theory, to obtain information about the inelastic collision cross section, the steepness of the intermolecular repulsion and the ratio η_v/η_s. The outcome of these calculations depends upon a number of assumptions, which have been discussed at some length.