Brillouin scattering study of equation of state of single component liquids

Abstract

Brillouin scattering experiments have been performed on a set of ten-single component liquids using a piezoelectric scanned, five-pass Fabry–Perot interferometer. The hypersonic sound velocities (vs) were determined as a function of externally applied pressure (P) from the observed Brillouin shifts. Experiments were performed at room temperature [T=(20±1)°C] and the pressure acting on the liquid samples was varied in the range 1–825 bars in steps of 100 bars each. By making use of modified Tait’s equation of state and assigning a linear pressure dependence to the adiabatic bulk modulus, we have constructed a theoretical model equation to express the pressure dependence of sound velocity as vs(P)=A0+A1P+A2P2. The experimental vs(P) values could be least-squares fitted to this equation within experimental error. From the values of the coefficients Ai’s we have determined the values of Tait parameters and the pressure coefficient of adiabatic bulk modulus. We found that the sound velocity, density, and bulk modulus all increase with pressure, the first two nonlinearly and the latter in a linear manner. These dependencies have been determined explicitly.