A Brillouin scattering study of sound velocity in single-component liquids up to 800 bar

Abstract

Describes the results of Rayleigh-Brillouin scattering experiments performed on a set of 10 single-component liquids. This set comprised associated and non-associated liquids. The samples were contained in a precision high-pressure cell mounted inside a temperature-controlled enclosure. This sample chamber provides excellent long-time pressure ( Delta P=0.05%) and temperature ( Delta T=+or-1 mK) stability. The Rayleigh-Brillouin spectra of the scattered light were studied at room temperature (20 degrees C), with the pressure acting on the samples varied from 1 to 800 bar. A home-made, piezoelectric-scanned, multipass Fabry-Perot interferometer was used to measure the Brillouin shift, which determines the hypersonic sound velocity (vs) of the thermally generated sound waves propagating in the scattering medium as a function of externally applied pressure. The authors have found that as the pressure was raised from 1 to 800 bar, vs(P) increased by more than 25% (typically) in most of the liquids considered in this study. They found that the vs(P) could be least-square fitted to a parabolic equation in P given by vs(P)=A0+A1P+AsP2 within experimental error. This equation is a manifestation of Tait's modified equation of state and the linear pressure dependence of the adiabatic bulk modulus in the modest-pressure regime.