Optimizing the Scintillation Kinetics of CsI Scintillator Single Crystals by Divalent Cation Doping: Insights from Electronic Structure Analysis and Luminescence Studies

Investigating the effect of codopants on the afterglow and pulse shape discrimination of Tl-doped CsI is very crucial for its successful applications in the fields of particle identification and medical imaging. The present work primarily focuses on the details of the electronic structure and luminescence properties of single crystals doped with CsI and codoped with Tl⁺, Sr²⁺, and Eu²⁺. Our results reveal that there is a remarkable acceleration in the scintillation decay of the γ radiation of CsI:Tl codoped with Eu²⁺ and Sr²⁺ ions. Further, the deep energy level traps as evidenced by electronic structure calculations as well as thermoluminescence studies are found to be responsible for the observed changes in pulse shape discrimination and suppression of afterglow.