Evaluation of Brillouin scattering intensities from rare gas crystals

A pure dipole induced dipole (DID) theory, which properly takes into account long range contributions to the effective atomic polarizability renormalization, is developed to evaluate the Brillouin scattering intensities for rare gas crystals (RGC). The DID effect is considered at all the orders by rigorously solving the self consistent equation for the effective atomic polarizability. To evaluate the contribution of distant atoms, which is significant in a cubic structure, the dipole propagator and the driving field phase factor have been both used without short-range approximations. The results obtained for the elastooptic coefficients are discussed in relation to other theoretical predictions. A comparison is made with the experimental data of Stoicheff and coworkers, directly calculating the measured quantities in all the reported scattering configurations. We conclude that pure DID effects will reproduce the experimental results in the case of neon and argon, while the discrepancies increase for krypton and xenon. This suggests that the overlap contributions to the atomic polarizability fluctuations, which has been already included in previous theories, cannot be neglected in heavy rare gas crystals.