Red luminescence in pure silica glass

Photoluminescence measurements of the 1.9-eV (red) emission were carried out on high-purity silica glasses subjected to y-ray irradiation. The time decay of the 4.8-eV-excited-luminescence indicates that the 4.8-eV absorption and the 1.9-eV luminescence arise at two different defect sites, and that an energy transfer occurs between the two defects. Comparison with electron spin resonance observations suggests that the defect responsible for the 1.9-eV luminescence is the non-bridging oxygen hole center (NBOHC: ≡Si-O). The 4.8-eV absorption band increases when the sample is heated in an oxygen atmosphere prior to y-irradiation, suggesting that the defect responsible is related to some form of excess oxygen. The defect is tentatively identified as a negatively charged non-bridging oxygen (≡Si-0) which is formed when a peroxy linkage traps a i-induced electron, (≡Si-0-0-Si≡ + e → ≡Si-0- + •O-Si≡). Both the NBOHC and the defect responsible for the 4.8-eV absorption must be present in the glass for the 4.8-eV band excited 1.9-eV luminescence to occur.