ODMR of Self-Trapped Excitons in AgCl Crystals: Analysis of Polarization and Intensity of ODMR

A phenomenological theory of the radiative decay of the self-trapped excitons (STE) in AgCl crystals at low temperatures is developed. The radiative decay of magnetic sublevels of the triplet STE is determined by singlet odd wave functions admixed into the lowest triplet wave functions by spin-orbit interaction and lattice vibrations. At 4.2 K, the transition probabilities between the triplet and the singlet states of the STE through the direct process of the spin-lattice relaxation turn out to be much larger than the corresponding probabilities between the sublevels of the triplet. The theory explains satisfactorily the ODMR signals observed at 4.2 K with the assumption of negative sign of zero-field splitting, D . Discrepancies found for signals of the STE at 1.6 K are discussed in terms of the polarization of the STE produced by the neighboring electron center.