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X-ray induced luminescence in single crystals of pure potassium iodide Usiskin, Sidney Robert

Abstract

The luminescent decay of pure potassium iodide has been measured under various conditions of temperature, annealing and x-irradiation time. The decay curves are found to be approximately of the form I(t) = [formula omitted] where I(t) is the luminescent intensity at the time t. Using a method that has been developed for the analysis of decay curves, numerical values for the decay constants, λi , and the trap populations Pi, have been estimated. The decay constants are found to be simple temperature functions of the form λi = [formula omitted] with the activation energies, Ei, lying between 0.4 and 0.8 ev and escape probabilities, Si, between 10⁴ and 10⁸ sec.⁻¹. The temperature dependence of the Pi is complicated and indicates that radiationless transitions strongly contribute to the emptying of traps at high temperatures. An irreversible increase in luminescent output produced by repeated x-irradiation without intermediate annealing is discovered; it points to considerable deviation from a first order decay mechanism in the case of slowly decaying traps. The mechanism of the irreversible effect is discussed on a semi-quantitative basis.

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