Landau-Placzek ratio of KBr single crystals—I

The Mandel'shtam-Brillouin and Gross scattering was measured for a series of purified KBr crystals. The ratio $\text{I}{}_{\mathrm{G}}\text{2I}{}_{\mathrm{MB}}$, which for a pure, perfect crystal would be the Landau-Placzek ratio, was found to vary with the type of reactive gas treatment used in the final purification. With these crystals both the longitudinal and mixed mode bands were observed with θ and φ equal to 90°. The ratio $\text{I}{}_{\mathrm{L}}\text{I}{}_{\mathrm{M}}$ was in agreement with calculated intensity ratios and the Δμ for these bands gave C₁₁ + C₁₂ = 41.6 GPa and C₄₄ = 5.18 GPa.