Temperature evolution of the charge transfer band and the vibronic interaction in a ZnS : Cr crystal

The temperature dependence of the charge transfer band in a ZnS : Cr crysta l is studied in the temperature range between 4.2 and 300 K in the waveleng th range corresponding to the Cr2+ --> Cr1+ photoionization transition. The dependence is analyzed by the method of a generating function based on the passage from the spectral to the time representation. This method was used for determining constants of vibronic interaction of the chromium ion with totally symmetric and tetragonal vibrations. The comparative smallness of these constants and corresponding relaxation energies is explained by a str ong hybridization of the 3d orbitals of the impurity with ligand (band) sta tes.