F(Br-) Center in Na-doped BaFBr

Absorption spectra of the F(Br-) center perturbed by the nearest neighbor Na+ ion in BaFBr:Na single crystals were measured. By using the dichroic bleaching technique, the doped Na+ ion was confirmed to replace one of the five Ba++ ions surrounding the F(Br-) center below 250 K, keeping the C4 symmetry of F(Br-). Above 250 K, the perturbed F(Br-) center converts to an isolated F(Br-) center.