Color Centers and the Thermoluminescence Mechanism in LiF

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Abstract
Color‐center transformations in pure and dosimetry grade LiF have been studied over the wavelength range 105–750 nm. Both impurity‐ and irradiation‐induced optical absorption were measured, the latter by a relatively high x‐ray exposure at room temperature. Thermal and optical treatments were chosen to induce transformations which are easily related to the thermoluminescence (TL) process. The results demonstrate the following for dosimetry LiF: The TL‐associated 310‐nm absorption results from trapped electrons. The TL process intimately involves V 3 centers (113‐nm absorption band). The centers causing the 225‐nm band (Z 3 band) and those causing the 137‐nm impurity band may both be involved in the sensitization (and supralinearity) phenomenon. A complete model for the TL is presented and discussed. Not so important to the TL is a broad apparently intrinsic absorption from 120–200 nm which is induced by irradiation in both pure and dosimetry LiF.