  We investigated the kinetics of H(II) centers (=Ge'-H) in natural silica
under repeated 266nm UV irradiations performed by a Nd:YAG pulsed laser. UV
photons temporarily destroy these paramagnetic defects, their reduction being
complete within 250 pulses. After re-irradiation, H(II) centers grow again, and
the observed recovery kinetics depends on the irradiation dose; multiple 2000
pulses re-irradiations induce the same post-irradiation kinetics of H(II)
centers after each exposure cycle. The analysis of these effects allows us to
achieve a deeper understanding of the dynamics of the centers during and after
laser irradiation.
