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UBC Theses and Dissertations

Thermal decay of the luminescence of KBr Williams, Gerald


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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