SULFATE IONS IN ALKALI HALIDE CRYSTALS: INFRARED ABSORPTION AND EFFECTS ON ADDITIVE COLORATION

Single crystals of KC1 containing sulfate ions have exhibited a large number of IR absorption peaks unless the crystals also contained an excess of divalent cations, in which case the spectra consist chiefly of 3 prominent absorban ces. This paper reports observations on crystals where the divalent cation concentration was low enough so the spectra were complicated. Progress was made in accounting for the peaks observed. A crystal-to-melt distribution ratio for sulfate ions is reported which makes it convenient to estimate the sulfate concentration for a crystal grown from a melt of known composition. Since sulfate ions bear a double charge, one expects their incorporation in an alkali halide crystal to be accompanied by the formation of negative ion vacancies. If such is the case, some pro nounced effects upon the behavior of F centers may result. Experiments with crystals contain ing sulfate ions which were additively colored. The sulfate ions were reduced to other divalent anions (e.g. peroxide) by the coloration process; these anions then markedly affect the bleaching of F centers. (Author) Report on A Magnetic Study of Color Centers in Alkali Halides.