Time-resolved spectroscopy of the Eu²⁺luminescence in KCl:Ba²⁺, Eu²⁺KCl:Sr²⁺, Eu²⁺and KBr:Sr²⁺, Eu²⁺

Abstract

Fluorescence kinetic studies of the Eu2+ luminescence in freshly quenched crystals of KCl:Ba2+, Eu2+, KCl:Sr2+, Eu2+ and KBr:Sr2+, Eu2+ are reported. The measurements were carried out at 300 K, at low concentrations of the dopants, and after the crystals were subjected to severe quenching treatments. The results obtained suggested that small complexes of Ba2+-Eu2+ are preferentially formed in the lattice of potassium chloride. At variance with this situation, evidence for the preferential formation of Sr2+-Eu2+ close pairs was not found in the doubly doped crystals of KCl:Sr, Eu and KBr:Sr, Eu. These results are in good agreement with the ionic radius criterion proposed by Rubio and co-workers (1985, 1987, 1988, 1989) to predict pairing between two impurity ions in a solid material.