Absorption band at 7.6 eV induced by γ-irradiation in silica glasses

Optical absorption of defects induced by gamma -irradiation in both natural and synthetic silica is experimentally investigated in the vacuum-ultraviolet (UV) range. Our results show that gamma -rays, in a dose range of 1000 Mrad, induce an absorption band centered at 7.6 eV, the so-called E band, whose growth kinetics is not related to gamma -activated precursors but to defects of the glassy matrix directly induced via the breaking of Si-O beads occurring under gamma -irradiation. Moreover, we observe that gamma -rays do not bleach the E band present in some silica samples before irradiation, so ruling out that the associated defects can be precursors of the paramagnetic E' centers, also induced by gamma -irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.