Scintillation and anomalous emission in elpasolite Cs 2LiLuCl 6:Ce 3+

Abstract

The luminescence and scintillation properties of Cs 2LiLuCl 6:0.5%Ce 3+ are presented. Special attention is devoted to a 9.4 ns fast emission at 275 nm that can only be excited via the highest cubic field 5d e state of Ce. Contrary to Cs 3LuCl 6 and Cs 2LiYCl 6, where the same type of fast emission was observed, the emission in Cs 2LiLuCl 6 is still observed at room temperature. Assuming that the 5d e state is located inside the host conduction band (CB), we propose that the emission originates from a mixed state at or just below the bottom of the CB and ends at the 4f ground state of Ce 3+. To proof this model we studied the thermal quenching of the anomalous luminescence and performed X-ray photoelectron spectroscopy. A model for a temperature-activated energy transfer from the anomalous state to the lowest 5d t excited state of Ce 3+ explains most of the results. Besides the 275 nm emission, the material shows 5d t–4f Ce 3+ emission at 370 and 406 nm and 2 ns fast core-valence luminescence when excited with 16–22 eV photons. The scintillation properties of Cs 2LiLuCl 6:Ce are briefly discussed.