Second-Order Raman Scattering and Its Resonant Behavior in Thallium Halide Crystals

Abstract

Second-order Raman scattering spectra have been measured in TlBr and TlCl single crystals at 77 K. In both crystals, the resonant behavior of the overtone band of LO phonon with q∼0 (the 2LO(Γ) band) is explained by the theory of Ganguly and Birman. Combination bands of two phonons with large wave vector have been observed in the spectra. The dependence of their intensities on the incident photon energy has been found to be different from that of the 2LO(Γ) band, which shows that the scattering processes are different.