Photoluminescence of oxygen-deficient-type defects in γ-irradiated silica glass

We studied the photoluminescence (PL) band in high-purity oxygen-deficient-type silicas both before and after high-dose γ-irradiation. With a high γ-irradiation dose of up to 10 MGy, a new PL band was induce at 3.9 eV and observed under excitation by 4.66 eV photons, along with the previously observed 2.25, 2.7 and 4.3 eV PL bands. Among the samples we investigated, this PL band was found only in high-dose γ-irradiated oxygen-deficient-type silica glass with the highest oxygen-deficient-associated defect structures [oxygen vacancy, E′ center and Eδ′ center]. These results indicate the possibility that this PL band is associated with an extreme oxygen-deficient-associated defect structure, at present unknown, in the silica glass which was introduced during the manufacturing process and which is enhanced by γ-irradiation.