Temperature dependent scintillation properties of pure LaCl(3).

The scintillation yield, scintillation decay, and x-ray excited emission of pure LaCl(3) was studied as a function of temperature between 80 and 600 K. Two broad band emissions centered around 325 nm and 400 nm were identified and correlated to emissions from two localized exciton states named STE(1) and STE(2), respectively. Different temperature dependences were observed for the short and long wavelength band intensity. From 80 to 150 K, the 400 nm band intensity increases at the expense of the 325 nm band intensity. Above 150 K almost all emission is in the 400 nm band. From 150 to 600 K, the intensity of this band decreases and its lifetime shortens. These results are analyzed and interpreted with a model that comprises the creation of STE(1) and STE(2) self-trapped excitons, thermally activated quenching of STE(1) and STE(2) emission, and thermally activated transfer of excitation energy from STE(1) to STE(2).