Commercially available LaBr3:5% Ce3+ scintillators show with photomultiplier tube readout about 2.7% energy resolution for the detection of 662 keV γ-rays. Here we will show that by co-doping LaBr3:Ce3+ with Sr2+ or Ca2+ the resolution is improved to 2.0%. Such an improvement is attributed to a strong reduction of the scintillation light losses that are due to radiationless recombination of free electrons and holes during the earliest stages (1–10 ps) inside the high free charge carrier density parts of the ionization track.

The scintillation properties of pure SrI 2 and SrI 2 doped with 0.5%, 0.86%, 2%, and 5% europium were studied. Different techniques were used to measure -ray excited pulseheight and scintillation decay time spectra, and to perform X-ray excited and optically excited emission spectroscopy. Eu 2+ emission and trapped exciton (TE) emission was observed in SrI 2 : Eu 2+ samples. These emissions were studied as a function of temperature, Eu concentration, and sample size. A spectral overlap was observed between Eu 2+ excitation and emission spectra, the amount of overlap depends on temperature. The light yield, energy resolution and luminescence decay profiles reveal also a dependence on temperature, sample size, and Eu concentration. The observations were analyzed and interpreted in terms of two separate models. One model consists of the relation between TE andEu 2+ emission and the other deals with self absorption processes.

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