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Thermal decay of the luminescence of KBr Williams, Gerald

Abstract

An apparatus for the measurement of the luminescent decay of phosphors has been designed. Decay times in the range 2 to 10⁴ seconds may be recorded. The decay of pure single crystals of KBr has been observed at sixteen temperatures in the range -77°C. to 240°C. Luminescence disappears at higher temperatures. The decay curves were analyzed graphically into a sum of exponentials. The half-lives of these components were found to be independent of the intensity of excitation of the crystal. The half-lives varied with temperature according to the relation [formula omitted]. The decay is then interpreted as being governed by a series of trapping levels in the crystal, which would produce a variation of decay constant with temperature given by [formula omitted]. Applying this interpretation to the observed decay, seventeen trapping levels, with thermal activation energies φ[subscript]n have been obtained. The values of φ[subscript]n range from 0.42 e.v. to 1.05 e.v. The spectrum of the luminescence at room temperature has been measured, and is found to be a wide band with a peak at 5100 A°.

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