Gamma irradiation induced photochemical reactions in V-doped borate glasses

Glasses of the composition XNa2O . 4Al2O3(96-X)B2O3 (mole%) where X=10, 20, 30 to which 0.03 g V2O5 per 100 g glass was added, were prepared by normal melting. Their absorption characteristics together with the corresponding V-free base glasses were determined before and after gamma irradiation. The characteristic spectra of the unirradiated glasses show absorption bands at 315, 470, 560-580, 610-650, 700-870, and 860-1000 nm, indicating the presence of vanadium ions in more than one oxidation state, viz, V5+, V4+, and V3+. Gamma irradiation of V-containing glasses causes the formation of color centers in the glass matrices, with absorption bands at 330, 500, and 610 nm, and photoreduced [V3+] and [V2+] ions with absorption bands at 350-355, and 530-570 and 520 nm, respecively. Photoreduced [V4+] may also be formed, giving rise to absorptions at 690-700 and 750-800 nm. The induced vanadium ions are found to absorb at shorter wavelengths than the intrinsic ones. An explanation based on the difference in the field energy of the two states is given