Temperature Dependence of Raman Spectra of Cuprous Halides

Abstract

Abstract The temperature dependence of the half linewidth and frequency shift of Raman lines in cuprous halides are investigated in the temperature range from 4.2 to 300 K. As for the LO and TO mode of CuI and CuBr, and the LO mode of CuCI, the experimental linewidth and frequency shift are in good agreement with the theoretical ones which have been calculated in terms of three‐phonon interaction. In order to explain the temperature dependence of a strong combination mode in conjunction with the TO phonons of CuCI, the hybridization theory proposed by Ruvalds and Zawadowski is employed in which hybridization between a two‐phonon and a single phonon state is postulated. A numerical analysis is made assuming that the acoustic combination mode (TA + LA) hybridizes with the TO mode. The anomalous frequency shift and line broadening of the strong combination line are explained by the temperature dependence of the coupling constant of two acoustic phonons (between TA and LA mode). The linewidth and frequency shift of the TO mode can be explained in some degree by this hybridization theory.