Scintillation properties and anomalous Ce3+ emission of Cs2NaREBr6:Ce3+ (RE = La, Y, Lu)

We report the optical and scintillation properties of the Ce3+-doped bromoelpasolites Cs2NaREBr6 (RE=La, Y, Lu). The gamma-ray scintillation light yield of these materials varies from 6000 to 17 000 photons per MeV absorbed gamma-ray energy. At room temperature (RT), the gamma-ray scintillation decay curves for all compounds show a fast component of 61 ns, whereas the intrinsic Ce3+ decay time is 30 ns. The scintillation mechanism in elpasolites is addressed. In Cs2NaLuBr6:Ce3+ and Cs2NaYBr6:Ce3+, we observe for the first time the so-called Ce3+ anomalous emission in bromide compounds. This emission previously observed for chloride compounds is an ultrafast Ce3+ emission with a selective excitation mechanism. The decay time of the anomalous emission at 10 K in bromide compounds (similar to 7.80 ns) is faster than that in chloride compounds (similar to 9.90 ns). Two bands of the anomalous emission are resolved for the first time. The mechanism behind this emission is discussed.