Vacancy‐induced splitting of excited states and the structure of Sn2+V centres in alkali halides

Abstract

AbstractThe polarization characteristics are calculated for the A and C emissions of Sn2+V centres in alkali halides, taking into account the rearrangement in the electronic level system of the excited sp states in the course of relaxation. The light absorption processes are considered in the approximation of a weak crystal field. The emission processes are described by a model in which the interaction of the optical electrons of impurity ions with Eg lattice vibrations (JTE) is assumed to be the principal, and the spin–orbit interaction and the interaction with T2g vibrations are taken into account as additive corrections. It is also assumed that in Sn2+V centres the influence of the cation vacancy V is small as compared with JTE. Comparing the results of the calculation with the experimental data, the order of three tetragonal minima on the adiabatic potential energy surface (APES) of the 3P state of Sn2+V centres is established which is consistent with the order of the corresponding minima of 1P state. It is shown that in both excited states Z minima are the lowest ones. The vacancy‐induced splitting of the relaxed excited A state is found to be about 10−2 eV. The limit values are determined for the polarization degrees of A and C emissions at various temperatures, the parameters are found and the structure is discussed for the Sn2+V centres in alkali halides.