RAYLEIGH-BRILLOUIN SCATTERING AND COMPRESSIBILITY OF WATER

Rayleigh-Brillouin ratio for a nonrelaxing fluid is calculated for water from theory and shown to agree with the measured values, within the experimental errors. The differences between ultrasonic and directly measured compressibilities are shown to be proportional to the entropy-fluctuation scattering of water, for the temperature range 0-100°C and pressures up to 800 bar. Deviations between ultra- and hypersound velocities are shown to equal the deviations between ultrafrequency and zero-frequency velocities over the temperature range 0-80°C, within the experimental errors. All of these results agree with the evidence given previously to support the conclusion that equilibrium is not completely maintained during ultrasonic velocity measurements on water. © 1979 American Chemical Society.