RESONANT RAMAN-SCATTERING IN CRYSTALS WITH SELF-TRAPPING EXCITONS

The multiphonon resonant Raman scattering spectra in NaI and LiH (LiD) cubic crystals characterized by self‐trapping of excitons are investigated experimentally. The first‐order scattering cross section is established to depend on the wave vector. The frequency dispersion of the secondorder scattering cross section is in agreement with the theory. The 1S and 2S excitons as intermediate states as well as the damping of excitons are taken into account. The temperature dependence of the second‐order intensity in both luminescence and resonant Raman scattering is studied in the region of 2 to 300 K. This dependence is shown to weaken with the shifting of the exciting light frequency from the exciton band bottom towards the red. The temperature behaviour of the frequency dispersion of the second‐order Raman cross section at the temperature change in the crystals with self‐trapping excitons is discussed. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA