Investigation of Sm2+ as a near-infrared emitting activator for NaI scintillators

• Published in: Optical materials Vol. 157
• Main Authors: van Aarle, Casper, Biner, Daniel A., Krämer, Karl W., Dorenbos, Pieter
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024
• Subjects: NaI; Near-infrared emission; Samarium; Scintillator; Single crystal; Scintillator; Samarium; Single crystal; NaI; Near-infrared emission
• ISSN: 0925-3467
• DOI: 10.1016/j.optmat.2024.116094

NaI is the most commonly used host lattice for scintillators, which makes it interesting to further improve its scintillation properties. Many alternative activators have been tried instead of the conventionally used Tl+. In this work, Sm2+ is used as an near-infrared emitting activator for NaI to study whether it is suitable for readout with silicon based photodetectors. NaI single crystals (co-)doped with 0-0.2% Tl+ and 0.2%–2% Sm2+ were grown by the vertical Bridgman technique. The emission of the samples was studied under optical and X-ray excitation. It is shown by photoluminescence decay studies that Tl+ works as a sensitiser for Sm2+. The samples indicate the formation of multiple (at least 5) different Sm2+ emission sites. Annealing the samples changes their emission intensity and scintillation properties. NaI:Sm2+ shows great similarities with its Eu2+-doped counterpart. Finally, it is demonstrated that NaI:Sm2+ can be read out with silicon photomultipliers and an energy resolution of 11% has been attained. •At least 5 different emitting Sm2+ sites have been identified.•Co-doping NaI with Tl+ and Sm2+ quenches the emission of Tl+, but not of Sm2+.•Energy transfer from Tl+ to Sm2+ takes place.•Annealing of NaI:Sm2+ more than doubles its light yield.•Even at room temperature, high ionic mobility creates precipitates containing Sm2+.