Influence of γ-irradiation on some properties of NaCl:Eu++ crystals. 2

The room temperature colouration process of NaCl:Eu++ crystals strongly depends on both the dopant concentration, represented by the absorption coefficient α(e/sub g/), and the dopant dispersion state as well. It has been found that within the UV spectral range either some V-type absorption bands appear or only the background absorption increases. For heavily irradiated crystals the clustering of halogen-interstitial results in the formation of dislocation loops. In dependence of the dopant concentration the colourability of as received crystals is either larger (α(e/sub g/) < or approximately 50 cm-1), or smaller (α(e/sub g/) > or approximately 50 cm-1) of that characteristic of the solution treated ones. The difference in the effectiveness of the halogen-interstitials trapping-process has been explained in terms of the various structure and/or composition of the europium-related aggregates and/or precipitates. (author)