Comparison of the Spectral Characteristics of Chromium-Containing Crystals of the Calcium Gallogermanate Type with Their Structural Features

The molecular refractions and characteristics of the circular dichroism spectra of unactivated and chromium_activated La3Ga5.5Ta0.5O14, La3Ga5.5Nb0.5O14, La3Ga5GeO14, La3Ga5SiO14, Sr3Ga2Ge4O14, and Ca3Ga2Ge4O14crystals are compared with their structural parameters. Correlations between the molecular refractions and the structural distortions responsible for the optical activity of crystals and correlations between the characteristics of circular dichroism bands of defects and chromium ions and the interatomic distances in polyhedra and their distortions are found. The calcium gallogermanate structures exhibit a unique correspondence between the electronic configuration of host ions and the local symmetry.