ENERGY-TRANSFER IN SODIUM-BROMIDE SLIGHTLY DOPED WITH COPPER AND MANGANESE IONS

The optical properties (emission, excitation and lifetime data) of NaB r slightly doped with Cu+ and Mn2+ ions have been studied in the prese nt investigation. The analysis of the spectroscopic data obtained indi cated that the Cu+ --> Mn2+ energy transfer takes place in this materi al even at very low impurity concentrations and after the crystals are subjected to severe quenching treatments. This fact suggested that th e donor and acceptor ions are not randomly distributed in the lattice of sodium bromide but rather occur as small impurity complexes of Cu+- Mn2+. The data shown in this paper substantiate the ionic radius crite rion proposed by Rubio et al, which predicts pairing between two impur ity ions in a crystal when their average ionic radius equals the radiu s of the host ion they replace.