Rare-Earth Ions in the Alkali Halides. I. Emission Spectra of Sm2+-Vacancy Complex

Measurements have been made of the crystal-field splitting of the FJ7 energy levels of the 4f6 configuration of the Sm2+ ion which is dissolved in a number of alkali-halide lattices. Crystal-field term assignments were made from the results of polarized-emission measurements. Observed crystal-field splittings are compared to those predicted from point-charge models. Contributions to the total crystal field are considered to include that due to the presence of a nearest-neighbor cation vacancy as well as that due to displacements, from normal lattice positions, of the nearest-neighbor halide ions and the Sm2+ ion. The splitting is shown to arise in part from a displacement of the Sm2+ and the cation vacancy toward each other. The extent of the validity of the use of a point-charge model for this case is discussed. © 1964 The American Physical Society.