Crystals of Eu-doped material, with aggregate centers, were characterized by photoluminescence measurement at 10 to 550K, and by thermostimulated luminescence. The aggregates were created by annealing samples, which contained 0.42mol% of metallic Eu, in air at 430 to 520K. The crystals contained nanocrystals and precipitates of Eu2+ compounds (probably CsEuBr3, Cs4EuBr6 and EuBr2), that emitted in bands that peaked at 516, 490 and 409nm, respectively, as well as isolated dipole centers of Eu2+-VCs that emitted in a band that peaked at 431nm. The excitation energy transfer between isolated dipole centers (Eu2+–VCs) and aggregate centers, and the effect F-like centers upon the process, were considered. It was shown that de-excitation of the Eu2+ ions took place mainly through the luminescence of aggregate centers.

Luminescent Spectroscopy of Eu2+ Centers in CsBr:Eu Single Crystals at 10–550K. Y.V.Zorenko, R.M.Turchak, W.Gryk, M.Grinberg: Journal of Luminescence, 2004, 106[3-4], 313-20