Decrease In Absorption Intensity Research Articles

Silicate glasses exposed to high-energy radiation develop three visible absorption bands sircilar to the F- and V-band in alkali halide crystals. The fanction of cerium in suppressing formation of these bands was studied spectrophotometrically in glasses with compositions of 20 R/sub 2/O, 10 BaO, 70 SiO/sub 2/, and 0.03 mole% CeO/sub 2/ (R/sub 2/O: Li/sub 2/O, Na/sub 2/O, K/sub 2/ O). Glass specimens of about 0.1 mm in thickness were irradiated with x rays of 42 kev, 10 ma, and changes of their absorption spectra in the range of 230 to 600 m mu were measured with the Beckman photoelectric spectrophotometer. As the absorption changes were found to be caused not only by color centers but also by other sources such as the valency change of cerium ion, the change due to color centers was separated from the others by heating the irradiated specimen at l5O deg C for 30 min; the decrease in absorption intensity by the heating was taken as the absolute change of the absorption dae to formation of color centers. The experimental results showed that trivalent cerium ions suppress development of the three absorption bands equally. Thus trivalent cerium ions are effective in preventing formation ofmore » either of those structural imperfections associated with trapped electrons of positive holes. As to the valency changes of cerium ion itself, a small part of trivalent cerium ions was found to lose their electron upon irradiation by the reaction Ce/sup 3+/ + h nu -- STACe/sup 3+/ with positive holel + e/sup -/. (auth)« less