Scintillation and Optical Properties of BaBrI\!:\! Eu²⁺ and CsBa₂ I₅\!:\! Eu²⁺

This paper reports on the scintillation and optical properties of the recently discovered europium doped BaBrI and CsBa2I5scintillators. Single crystals of BaBrI and CsBa2I5were grown from the melt by the vertical Bridgman technique. Crystals were doped with 8% and 4% Eu2+for BaBrI and CsBa2I5, respectively. These crystals have higher optical quality and present improved scintillation performance compared to the previously reported values. An estimated light yield of 97,000±5,000 and 102,000±6,000 photons per MeV (ph/MeV) of absorbed gamma-ray energy is now measured for BaBrI:8%Eu2+and CsBa2I5:4%Eu2+, respectively. A better energy resolution has also been observed. BaBrI energy resolution for the 662 keV full absorption peak (FWHM over peak position) decreased to 3.4±0.2% and CsBa2I5:4%Eu2+energy resolution decreased to 2.55±0.2% . Additional measurements show both scintillators with an excellent light yield proportionality. Finally, based on optical and x-ray excited emission spectra and decay curves, energy transfer mechanisms in BaBrI and CsBa2I5scintillators are briefly discussed.