Non-radiative transitions in the oscillating field model

The model of energy levels crossing in the theory of non-radiative transiti ons (NRT) has been developed. In the framework of this model NRT are due to the crossing of purely electron energy states of the impurity ion caused b y ligands thermal vibrations. Analytical expressions describing the tempera ture dependence of the NRT probabilities are obtained. The results of calcu lation of the T-3(2) --> (3)A(2) NRT for the tetrahedrally coordinated Cr4 ion are reported. An accordance between the theoretical calculations and e xperimental data is discussed. (C) 2001 Elsevier Science B.V. All rights re served.