Critical Sound Absorption in Xenon

Ultrasonic attenuation in Xe has been measured along a near-critical isochore at frequencies in the range 0.4-5 MHz and at temperatures above $T_c$. Hypersonic attenuation values obtained from Brillouin linewidths are also cited. It is shown that the critical attenuation per wavelength depends on temperature and frequency through a single reduced variable ${\omega }^{*}=\frac{\omega }{{\omega }_{\mathrm{D}}}$, where the characteristic frequency ${\omega }_{\mathrm{D}}=\left(\frac{2\Lambda }{\rho C_p}\right){\xi }^{-2\mathrm{}}$. The experimental results are compared with numerical calculations based on a recent theoretical formulation by Kawasaki.