ELECTRONIC STRUCTURE OF THE F CENTER IN THE ALKALINE EARTH OXIDES

Abstract

The energy levels and wave functions of the ground and first few singlet and triplet excited states of the F center in MgO, CaO, and SrO were calculated as a function of the nearest neighbor ion positions. Configuration coordinate curves for A/sub 1g/, E/sub g/ and T/sub 2g/ displacements have been constructed and used to interpret the absorption and luminescence bands of the F center. The energy of the /sup 1/A/sub 1g/ ..-->.. /sup 1/T/sub 1u/ transition was set near the experimental value in each case by adjusting certain parameters in the model. The calculated energy level schemes partially support the interpretations of published experimental data on the luminescence bands in MgO and CaO and suggest that the /sup 3/T/sub 1u/ ..-->.. /sup 1/A/sub 1g/ luminescence in SrO should occur at roughly 0.4 eV. A luminescence band associated with the F center in SrO has not yet been reported. The calculations of the Jahn--Teller coupling constants indicate that the /sup 3/T/sub 1u/ state is strongly coupled to the E/sub g/ vibrational mode in CaO and to the T/sub 2g/ mode in MgO and SrO.