Role of Crystal Structure in theF-Center Spectrum of Cesium Halides

Spectral positions of the $F$ centers of cesium halides (body-centered cubic structure) are computed by applying a purely geometry-dependent theory, the point-ion-lattice approximation of Gourary and Adrian. Results are compared with those previously obtained in alkali halides with NaCl structure (two super-imposed face-centered cubic lattices). Although theoretical results coincide well with the Mollwo-Ivey relation regardless of type of crystal structure, experiments show large deviations from this relation in certain cases. Since the point-ion-lattice approximation does not predict these deviations, it is concluded that within this approximation difference of geometry alone has insignificant effect on spectral positions of $F$ centers in the alkali halides, and that the point-ion-lattice method is not sufficient for their computation.