Sound velocity and sound attenuation measurements by dynamic light scattering

Dynamic light scattering (photon correlation spectroscopy) has been applied to the determination of sound velocity and sound attenuation from the Brillouin component of the frequency spectrum scattered from a fluid sample transversed by a laser beam. In this paper the time-resolved determination of the Brillouin component is described. The measurement of the linewidth allows an accurate determination of the sound attenuation, while the central frequency is connected to the adiabatic sound velocity. Sound attenuation and sound velocity measurements are presented for the new refrigerant pentafluorethane (R125). The accuracy and possible systematic errors of this technique are discussed and compared to those obtained from other spectroscopic and acoustic techniques.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado. U.S.A.