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

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