An experimental study was made of post-irradiation kinetics of point defects generated in natural silica (a-SiO2) by ultra-violet photons (266nm) of a Nd:YAG pulsed laser. Isothermal time dependences of the ultraviolet-induced centers were investigated by electron spin resonance spectra recorded at different delays from the laser exposure. The measurements revealed 2 distinct processes active for some hours after the irradiation: the partial annealing of the E’γ centers (Si.) and the increase of the H(II) defects (=Ge.---H). The results were interpreted within the framework of the models concerning the diffusion and the recombination of atomic and molecular species occurring in the SiO2 matrix. New insights on both the reduction of E’γ centers and the growth of H(II) centers were obtained, suggesting a crucial role of the diffusing molecular H in the structural changes of defects observed in the silica specimens after the UV laser exposure.

Post-Irradiation Kinetics of UV Laser Induced Defects in Silica. M.Cannas, S.Agnello, R.Boscaino, S.Costa, F.M.Gelardi: Nuclear Instruments and Methods in Physics Research Section B, 2002, 191[1-4], 401-5