Absorption spectra of gamma-irradiated sodium phosphate glasses containing vanadium

The optical absorption spectra of nominally pure and V-doped sodium phosphate glasses have been measured from 200 to 1100 nm before and after gamma-ray irradiation. The induced absorption spectra, calculated as the difference between the spectra of the irradiated and the unirradiated 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 cut-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 of the induced bands depends on the irradiation dose, the glass composition and also on the V2O5 content. The response of the phosphate glass to gamma-ray irradiation is related to the formation of characteristic defects and colour centers, to the possible photochemical effect of the transition metal in the glass, and also to the possible approach of saturation after a certain irradiation dose. The suppression or retardation of the vanadium present in phosphate glasses in the creation of induced defects is also considered. (orig.)