Multiple Interconversions of theE′and Oxygen-Hole Defect Centers in High-Purity Amorphous Silica during Anneal-Interrupted x Irradiation

Multiple interconversions of $E^{\prime }$ centers and peroxy radicals have been observed for the first time by means of anneal-interrupted x-irradiation experiments. It is shown that each of these defects can serve as the precursor of the other; under thermal anneal an $E^{\prime }$ center can convert to a peroxy radical due to the capture of an oxygen molecule, and under irradiation the peroxy radical can covert to an $E^{\prime }$ center due to irradiation-induced release of oxygen. The results for the defect production and anneal behavior are well described in terms of simple stretched-exponential defect-reaction kinetics.