Abstract
The exchange charge model of the crystal field is applied to calculate the complete energy level scheme of the Cr 4+ ions in Y 3 Al 5 O 12 using symmetry at the Cr 4+ position. Mixture of the spin-triplet states arising from the and terms of the 3 d 2 -electron configuration is shown to have a profound effect on the energy levels sequence. Large splittings of the orbital triplets originating from the “parent” T d symmetry are explained by large contribution of the low-symmetry component of the crystal field. Huang-Rhys parameter and effective phonon energy are evaluated from the experimental spectroscopic data available in the literature. Temperature-dependent probability of the nonradiative transition between the ground and first excited states is drawn; the emission band shape is obtained using the single configuration coordinate model.
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