A Correlation between the Spectral Location of the Absorption Bands Due to the Localized Centers and the Lattice Constant in Alkali Halide Crystals. Anionic Impurity Centers with S 2 ‐Configuration and F Center which Have Cubic Symmetry

For four anionic impurity centers with S 2 ‐configuration (H − , Cu − , Ag − , and Au − centers) and the F center in alkali halides, a correlation between the peak energy, E , of the absorption band concerned and the lattice constant, d is extensively investigated. All the results indicate that the Smakula (STSN) relation, E = ad − n , holds for every alkali family ( a and n are adjustable parameters). The values of exponent, n , derived from the analysis for all centers treated show a systematic variation with the defect center, the absorption band, and the alkali ion. It seems that the factor n expresses a degree of the lattice relaxation. In fact, a relation between the n ‐value and the Stokes‐shift Δ E concerned, is very simple. An empirical relation, Δ E = bn k , roughly holds and the constants b and k depend only on the crystal structures of the alkali halides.