MULTIMODE ASPECTS OF VIBRONIC INTERACTION IN OPTICAL-SPECTRA OF IMPURITY CRYSTALS

The role of the multi-mode vibrational spectrum of crystals with struc tural defects in optical phenomena such as intracenter absorption and luminescence, internal photoeffect, and resonant Raman scattering is e xamined. A comparison is performed between the quasimolecular model an d those with more comprehensive account of the electron coupling with the quasicontinual vibrational spectrum. It is shown, that the multi-m ode character of the impurity crystal vibrational subsystem must be ta ken into consideration to interpret adequately the optical experiments . A review of theoretical and experimental results concerning this pro blem is presented.