MODERN TRENDS Th4 QUASI-LiNEAR SPECTRA STUDIES

The data of the theoretical and experimental investigations of the luminescence and absorption spectra of different organic compounds (aromatic hydro-carbons and their derivatives, phthalocyanines and porphyrins, polyenes, etc.) in frozen polycrystal solutions are summarized and systematized. The recent data prove that quasi-line spectra are the sets of zero-phonon lines accompanied by their vibrational repetitions when the impurity arrange-ment provides insignificant heterogeneous line broadening and the electron— phonon interaction is sufficiently small, Extensive experimental data make it possible to conclude that in the organic systems under consideration such conditions may be realised by means of a matrix modification near the impurity centres. The characteristics of quasi-line spectra (namely, the well-resolved vibra-tional structure and the sensitivity to internal and external perturbations) are shown to be of use in solving different problems of molecular and crysta