抄録
The γ-irradiation of silica gel degassed for 24 h above 400°C produces visible color center (λmax=530 nm). The color center instantly disappears on exposure to H2 at room temperature and irreversible adsorption of H2 is concurrently observed. On the basis that color center is attributed to the positive hole due to substitutional impurity of Al in silica matrix, the yield of color center and H2 adsorption have been investigated as a function of Al content in silica gel deliberatly prepared by us from silicon tetrachloride to contain Al in the range of 10-35W/O. Absorbance at 530 nm, A530, due to color center as well as the amount of H2 adsorbed, (H2) ads, increase with the Al content in the matrix. A530/(H2)ads is 1.0×106 (0.D. unit g/mol) in these gels. This ratio is seen almost same with two samples of gel commercially available.
By assuming that 1 mol of H2 reacts with 2 mol of positive hole, the extinction co-efficient of color center at 530 nm is evaluated as 10×106 (g/mol•cm).
