E. V. D. van Loef, P. Dorenbos, C. W. E. van Eijk, K. W. Krämer and H. U. Güdel
Scintillation properties of K₂LaX₅:Ce³⁺ (X=Cl, Br, I)
Nucl. Instr. Methods Phys. Res. A 537, 232-236 (2005)                 

Abstract: The scintillation properties of K₂LaX₅ (X=Cl, Br, I) doped with 0.7% and 10% Ce³⁺, studied by means of X- and g-ray excitation are presented. Under X-ray excitation, Ce³⁺ emission is observed. At 100 K, it is peaking at 344 and 372 nm in the chloride, at 359 and 391 nm in the bromide, and at 401 and 439 nm in the iodide. For K₂LaCl₅:Ce³⁺, K₂LaBr₅:Ce³⁺, and K₂LaI₅:Ce³⁺ we measured light yields of 20,000–55,000 photons per megaelectronvolt (ph/MeV) of absorbed gamma-ray energy. K₂LaI₅:10% Ce³⁺ appears to be the best in terms of scintillation light yield, decay time, and energy resolution. It has a high light yield of 55,000 ph/MeV, an exponential decay with a decay time of 24±5 ns and an energy resolution (FWHM over peak position) for the 662 keV full-energy peak of 4.5±0.5%.