Determination of the Elastic Constants of Xenon Single Crystals by Brillouin Scattering

Abstract

Single crystals of xenon were grown and Brillouin spectra for various crystal orientations were obtained at a temperature of 156 °K. The spectra exhibited one longitudinal component and either one or two transverse components, depending on crystal orientation. From the observed Brillouin frequency shifts, the adiabatic elastic constants for xenon were evaluated. At 156 °K, $c_{11}=2.98\mathrm{}\pm 0.05$, $c_{12}=1.90\mathrm{}\pm 0.04$, $c_{44}=1.48\mathrm{}\pm 0.04$ in units ${10}^{10}$ dyn/${\mathrm{cm}}^2$ and the elastic anisotropy was found to be 2.74 ± 0.30. These values were compared with calculated values based on recent theories of lattice dynamics. Good agreement was obtained only with calculations that include all-neighbor interactions. It was also observed that the relative intensities of the Brillouin components were strongly dependent on crystal orientation. An analysis of this variation in intensity gave values of the ratios of the elasto-optic constants for xenon.