The absorption bands of Cr3+ ions in solutions, crystals and glasses
JSGT 1959 V43 T289-T307
The absorption spectrum of a transition metal ion is greatly influenced by the strength and symmetry of the electric field due to the surrounding atoms, ions, or molecules, known as ligands. Ligand-field theory shows how the positions and intensities of the absorption bands vary with this field, and for fields of octahedral and tetrahedral symmetry the energy levels may be expressed in an Orgel diagram in which the energy levels are plotted against a parameter which measures the field strength. Application of this theory to Cr3+ ions in solutions, crystals, and glasses leads to the conclusion that in glass the ion is surrounded by six oxygens in octahedral symmetry. The absorption bands predicted from this theory are in good agreement with those observed.
T. Bates & R. W. Douglas
