Kinetics of the diffusion of self-trapped holes in alkali halide scintillators

Abstract Previous measurements of the reorientation kinetics of V k centers (self-trapped holes) permit a determination of the diffusion coefficient at room temperature in NaI, KI, RbI and KCl. Utilizing these diffusion coefficients, we apply Waite's diffusion-limites reaction theory to calculate the time required for self-trapped holes to migrate to thallium centers in NaI(Tl), KI(Tl), RbI(Tl) and KCl(Tl). We also estimate the lifetime of an electron trapped at a thallium site as a Tl° center from thermoluminescence measurements. It is concluded that V k centers diffuse and are captured at thallium sites in a time less than or comparable with the scintillation pulse decay time for the alkali iodides, and that the very long hole-diffusion time in KCl(Tl) is consistent with the absence of a scintillation effect in that crystal.

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