Abstract of Publication No. 502
A. Bessiere, P. Dorenbos, C. W. E. van Eijk, K. W. Krämer, H. U. Güdel, C. de Mello Donega and A. Meijerink
LaI3:Ce3+ has the smallest band gap in the
LaX3:Ce3+ (X=F, Cl, Br, I) series and hence a potentially
higher scintillation yield. The luminescence properties of LaI3:Ce
were investigated by means of optical, X-ray, and g-ray excitation.
Unexpectedly, the compound is a poor scintillator at room temperature but
presents good scintillation properties for temperatures below 100 K where
Ce3+ emission is observed peaking at 452 and 502 nm with a yield of
16000 photons/MeV. The drastic thermal quenching of luminescence is
explained by the proximity of the Ce3+ lowest 5d excited state to the
host conduction band. Autoionization of Ce3+ therefore prevents any
scintillation effect at room temperature. The positions of Ce3+
levels relative to the host bands were estimated.