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UV Induced Afterglow in Europium-Doped Alkali Bromides at Low Temperature

This work presents a study of the afterglow (AG) luminescence induced by UV radiation at 20 K in Eu doped KBr. The analysis of the AG data reveals at least two components: one of them decays quickly during the first seconds after irradiation and the other one extends over several minutes. The excitation-emission spectra of the AG and the thermoluminescence (TL) for a KBr:Eu sample are compared with those measured under identical conditions for a pure KBr. We conclude that the origin of the fast-AG is mainly intrinsic and the slow-AG is dominated by the Eu impurity luminescence. We confirm that the excitation-emission bands of the slow-AG also appear in the TL suggesting a close relation between the slow-AG and the TL. Additionally we found another TL band in the pure crystal that could not be related to the AG.