Spectroscopic measurements and thermoluminescence of γ-ray colored LiF crystals

Light produced when heating materials which have been previously exposed to ionizing radiation is commonly known as thermoluminescence (TL). The structure of TL glow curves is characteristic of the material and is influenced by the impurities it contains as well as the type of defect centers generated by the irradiation. An extensive body of knowledge exists concerning TL. In the case of LiF, several efforts have been made to associate glow peaks with defect centers responsible for optical absorption, but up to now there is no certain attribution. In this work nominally pure LiF samples have been irradiated with gamma rays, then treated thermally and optically to change the concentration of electron color centers in a known way, and the resulting TL has been studied in conjunction with optical absorption. By comparing the glow curves from ambient temperature to 450 degreesC and the optical absorption in the purple-blue spectral region, it has been possible to establish a link between F-3(+) color centers and the low temperature region of the glow curve below 200 degreesC. Accurate spectroscopic measurements and theoretical fittings of the absorption spectrum in the UV-VIS spectral region have also been made in order to ascertain the possible role of other aggregate color centers in TL. (C) 2003 Elsevier B.V. All rights reserved.