Converting SrI2:Eu2+ into a near infrared scintillator by Sm2+ co-doping

The luminescence and scintillation properties of SrI2 single crystals doped with 5% Eu2+ and 0.05%, 0.2% and 0.5% Sm2+ are evaluated. X-ray excited and photoluminescence measurements show energy transfer from excited Eu2+ ions to Sm2+ ions. At a concentration of 0.5% Sm2+, the luminescence consists almost entirely of 740 nm emission from Sm2+ 5d-4f transitions. Co-doping SrI2:5% Eu2+ with Sm2+ provides a novel method to bypass the self-absorption problem encountered in large SrI2:Eu2+ crystals and, at the same time, provides a unique near-infrared emitting scintillator with a light yield of approximately 40,000 photons/MeV.