ABSORPTION-SPECTRA OF GAMMA-IRRADIATED SODIUM-PHOSPHATE GLASSES CONTAINING VANADIUM

The optical absorption spectra of nominally pure and V-doped sodium ph osphate glasses have been measured from 200 to 1100 nm before and afte r gamma-ray irradiation. The induced absorption spectra, calculated as the difference between the spectra of the irradiated and the unirradi ated glasses, exhibit three absorption bands at about 400 nm (3.10 eV) , 500 nm (2.48 eV) and 550 nm (2.23 eV) in the parent sodium phosphate glass, while the V-doped glasses show a broad composite ultraviolet c ut-off extending to 400 nm (3.10. eV) and two other visible bands with peaks at about 680 nm (1.82 eV) and 830 nm (1.49 eV). The intensity o f the induced bands depends on the irradiation dose, the glass composi tion and also on the V2O5 content. The response of the phosphate glass to gamma-ray irradiation is related to the formation of characteristi c defects and colour centers, to the possible photochemical effect of the transition metal in the glass, and also to the possible approach o f saturation after a certain irradiation dose. The suppression or reta rdation of the vanadium present in phosphate glasses in the creation o f induced defects is also considered.