Abstract
The spectrum of light scattered from thermal sound waves has been studied by Brillouin spectroscopy in molten potassium nitrate to provide information about the hypersonic velocity and the absorption of thermal waves. Brillouin spectra were investigated in a temperature range of 350–600 °C for scattering angles of 40 °–140 ° to determine the variation of the phonon velocity and attenuation as a function of temperature and frequency. The measurements did not reveal any difference between the sound velocities at a scattering angle of 40 ° (3 GHz) and at 140 ° (10 GHz), but the hypersonic velocities were all higher than the ultrasonic ones. In spite of this fact, considerable decrease in attenuation was observed within the investigated frequency interval, with the value at high frequency approaching the classical limit attributed to shear viscosity. These results indicate a relaxation frequency just below the measured frequency range. The relaxation time for the bulk viscosity coefficient was determined from two independent measurements: (1) the position of the Brillouin lines and (2) the width of these lines. A relaxation theory involving a single relaxation time has been applied and agrees with the experimental results. Subject Classification: 35.24, 35.35.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
