In situ observation of β-ray induced UV optical absorption in a-SiO2: Radiation darkening and room temperature recovery

We studied the optical absorption in the 3.0–6.2 eV range induced in bulk amorphous SiO2 by β-ray irradiation up to ∼1 MGy at room temperature. The induced absorption was measured in situ both during irradiation and in the post irradiation time. Our data evidence E γ ′ center as the main defect induced by irradiation and the partial decay of their absorption band at about 5.8 eV after irradiation. A quantitative analysis of the time evolution of the induced absorption shows that the transmission recovery observed after irradiation is compatible with the reaction of radiation-induced defects with H-related (H2, H2O) species diffusing in the amorphous matrix.