Cover Picture: Host structure dependence of light yield and proportionality in scintillators in terms of hot and thermalized carrier transport (Phys. Status Solidi RRL 8/2012)

Abstract

Energy resolving radiation detectors are used in security scanning, medical molecular imaging, and high-energy physics applications. Critical performance improvement in scintillation detectors depends on understanding what controls light yield and the proportionality of light emission to particle energy within a track of very high excitation density and radial gradients. Hot and thermalized electron transport and hole self-trapping are found to be three important controlling phenomena. The cover illustration, pointing to the Letter by Qi Li et al. (pp. 346–348), shows the conduction band structure of NaI from which hot electron group velocity was calculated. The group velocity along with thermalization time governs the hot electron range illustrated by the shaded circular area, which in turn affects the number of trapping centers encountered on the path to recombination with less mobile holes. Such considerations offer insight into the dramatic and previously unexplained difference of light yield and proportionality between the classes of complex halide scintillators exemplified by SrI2:Eu2+ and simple monovalent halide scintillators like NaI:Tl+.