Radiation-induced optical darkening and oxidation effects in As₂S₃ glass

Abstract

The long-wave shift of fundamental optical absorption edge with decreasing the sample’s transparency in the saturation region in the As₂S₃ bulk glass (2 mm thick) due to radiation treatment by ⁶⁰Co y-quanta with the average energy E = 1.25 MeV and accumulated dose Ф = 2.41 MGy is reported. The red shift (radiation-induced optical darkening effect) is detected within the period of 2-3 months after y-irradiation able to cause the well-known static radiation-induced optical effect. The detected decrease in the slope of curve in the fundamental optical absorption edge region after y-irradiation, resulting in the maximum difference of optical transmittance for the unirradiated and y- irradiated samples max at the level 33.5%, can be interpreted within the radiationinduced defect formation processes occurring in the structural network of glass. At the same time, as expected from literature, the observed decrease in the sample’s transparency at the level 33% upon radiation is plausibly caused by the accompanying radiation-induced oxidation processes that are the most probably related with appearance of As₂S₃ (arsenolite) crystals and S phases at the surface of y-irradiated sample, forming a white oxidized layer visible to the eye. The disadvantage of As₂S₃ glass to be selected as the best model object for X-ray diffraction study of y-radiation-structural changes, especially in respect to the first sharp diffraction peak, is considered.