Spectroscopy and anomalous emission of Ce doped elpasolite CS2LiYCl6

A 10 ns fast luminescence was observed at 270 nm in CS2LiYCl6:Ce3+ in addition to the 5d(t)-4f Ce3+ doublet emission at 370 and 405 nm. This anomalous luminescence occurs exclusively for an excitation of the 4f-5d(e) transitions of Ce3+ around 210 nm. It is not excited under across band gap excitation which makes it an uncommon phenomenon. The emission shows a large Stokes shift of 1.2 eV that must be related to an excited state with a very strong electron-lattice interaction or possible involvement of conduction band states. The 270 nm emission undergoes thermal quenching between 140 and 250 K while the 5d(t)-4f Ce3+ emission gains intensity. The shape of the decay time spectra of the 5d(t)-4f Ce3+ emission reflects a temperature activated transfer from the anomalous state to the 5d(t) lowest Ce3+ level.