Specific features of Raman scattering in crystals with a cooperative Jahn-Teller effect

A microscopic approach which permits Raman scattering in a dielectric cryst al is presented to be described in a uniform way. Additional features of th e temperature dependences in the spectrum of Raman scattering of phonons ar e obtained, arising owing to presence of low-lying nearly degenerated elect ronic levels typically occurring in crystals with Jahn-Teller phase transit ions. The changes in the populations of these levels may influence the temp erature dependences in Raman spectra, The theory describes also the electro nic Raman effect in these crystals. Copyright (C) 1999 John Wiley & Sons, L td.