The geometrical and electronic structures, and electron excitation energies, of the 1-center hole polaron state and of several possible intermediate states which corresponded to hole relaxation in this halide, were calculated by using the static embedded molecular cluster method. It was found that the calculated optical transition energies were close to the maxima of the transient optical-absorption spectra which were observed experimentally by using fs-spectroscopy. It was demonstrated that the experimentally observed spectra could be understood if it were assumed that the hole was first localized in the 1-center state, which then transformed into the 2-center state and finally into the VK center.

A.L.Shluger, J.D.Gale: Physical Review B, 1996, 54[2], 962-9