E. V. D. van Loef, P. Dorenbos, C. W. E. van Eijk, K. W. Krämer and H. U. Güdel
Influence of the anion on the spectroscopy and scintillation mechanism in pure and Ce³⁺-doped K₂LaX₅ and LaX₃ (X = Cl, Br, I)
Phys. Rev. B 68, 045108/1-9 (2003)                 

Abstract: The optical properties and scintillation mechanism in pure and Ce³⁺-doped K₂LaX₅ and LaX₃ have been determined under x-ray, g-ray, vacuum ultraviolet light, and synchrotron radiation excitation. Special attention is paid to the influence of anions X = Cl^–, Br^–, and I^–, and a comparison is made with properties of pure and Eu²⁺-doped KX compounds. The energies of the 5d excited states of Ce³⁺ have been determined, and the total crystal field splitting and the centroid shift are discussed. An excitation across the band gap creates a combination of self-trapped exciton (STE) and Ce³⁺ emission. These emissions are often anticorrelated when temperature or Ce³⁺ concentration is changed. Their ratio is related to the STE mobility and STE creation rate. Clear trends in the optical properties and scintillation mechanism are observed along the halide series.