Intensities of circular dichroism and absorption bands and the states of d ions in absorbing media: II. Tetrahedrally coordinated positions of d ions

Abstract

The factors affecting the band intensity in the circular dichroism (CD) and absorption spectra of tetrahedrally coordinated d ions in an absorbing medium (symmetry selection rules, structural position, and bond covalence) are analyzed. It is shown by the examples of the Cr4+ ion in Ca3Ga2Ge4O14 crystal and the Fe2+ and Fe3+ ions in SiO4 crystal that the symmetry forbiddenness of the transitions from orbitally degenerate states and the covalence of the d-ion-ligand bond lead to changes in the intensity of the corresponding CD bands in a wide range, beginning from zero. It is shown by the example of Ca3Ga2Ge4O14, LiAlGeO4, LiGaGeO4, and LiGaSiO4 crystals activated with Cr4+ ions that the preferred ion localization position corresponds to a higher effective symmetry.