Resonance Raman Scattering in Cuprous Halides

Resonant behavior of Raman cross-section is studied in CuCl, CuBr and CuI by using an argon ion laser and a tunable dye laser as the excitation light source. The results are in good agreement with existing theory demonstrating the significance of the discrete and continuum levels of excitons as the intermediate state of the transition. It is concluded that the 1 L O scattering cross-section near the resonance region is governed by the n =1 exciton level, while the exciton continuum contributes predominantly in the off resonance region. contrary to the cases of CuBr and CuI, higher exciton series ( Z 12 ) also plays an important role in CuCl, which fact is ascribed to the characteristic band structure of this material. As in CdS and ZnO previously reported, the observed frequency dependence of the 2 L O Raman intensity in CuCl is consistently interpreted in terms of the consecutive scattering of virtually created excitons by two phonons.