Abstract: LaBr₃:Ce and CeBr₃ crystals exhibit high light yield, fast decay, and good energy resolution. They are widely applied in γ-ray spectroscopy and space exploration. Therefore, it is essential to investigate their radiation damage effects. At present, changes in the luminescence behavior of these crystals after ionizing irradiation are not sufficiently studied. In this work, LaBr₃:Ce and CeBr₃ crystals were irradiated step by step with γ-rays. Radiation induced absorption coefficient (RIAC) spectra, photoluminescence (PL) spectra and PL decay curves were used to investigate the luminescence characteristic and decay kinetics of the crystals before and after irradiation. The results show that both crystals exhibit Ce³⁺ 5d→4f transition emission and self-trapped exciton (STE) broadband emission before irradiation. The overlap between the Ce³⁺ emission spectra and the excitation spectra of STE emission indicates that there may be the energy transfer process from Ce³⁺ emission to STE emission. The PL decay results show that the decay time of STE emission under 300 nm excitation is significantly longer than the intrinsic decay time measured under 450 nm excitation. It suggests that the STE emission under 300 nm excitation may involve two contributions: a fast process from direct STE excitation and a slow process associated with STE re-excitation by Ce³⁺ emission. After γ-ray irradiation, the RIAC values of both crystals gradually approach saturation with increasing cumulative irradiation dose. The relative STE emission intensity of LaBr₃:Ce crystal increases significantly compared with that before irradiation, and the decay time of STE emission under 300 nm excitation is prolonged. In contrast, no obvious changes are observed in the PL spectral shape or decay time of CeBr₃ crystal after irradiation. Combined with RIAC analysis, the enhanced STE emission in LaBr₃:Ce after saturation of radiation-induced absorption may be related to changes in the local distribution of radiation-induced defects, which enhances the energy transfer process from Ce³⁺ emission to STE emission. The prolonged STE decay time under 300 nm excitation may be associated with the increased relative contribution of the slow emission process. This investigation provides experimental evidence for understanding the irradiation induced luminescence behavior and radiation damage effects of LaBr₃:Ce and CeBr₃ crystals.

Key words: LaBr₃:Ce crystal, CeBr₃ crystal, radiation damage, photoluminescence, decay time