Spectroscopy of selected alkaline earth halides

Recently a number of alkaline earth halide scintillators doped with Eu²⁺ have been reported on. They are characterized by very good proportionality, high up to 100,000 photons/MeV light yield, and very good energy resolution, as low as 2.8% at 662 keV. Yet, one of the issues facing these materials is radiation trapping. Radiation trapping results from a small Stokes shift that creates considerable overlap between emission and absorption bands. As a result the scintillation light is absorbed and emitted multiple times, leading to a prolongation of the scintillation decay, potential light losses and degradation of energy resolution. Spectroscopic properties of various Eu²⁺ doped alkaline earth halides are presented. Materials studied include: SrI₂, BaI₂, BaBrI and other compounds. It appears that some compositions are less affected by radiation trapping.