Relation between the 1.9 eV luminescence and 4.8 eV absorption bands in high-purity silica glass

Photoluminescence measurements of the 1.9 eV emission were carried out on high-purity silica glasses subjected to γ-ray irradiation. The time decay of the luminescence, when excited by the 4.8 eV band, indicates that the 4.8 eV absorption and the 1.9 eV luminescence are caused by two different defects, and that an energy transfer occurs between the two defects. Comparison with electron spin resonance observations shows that both the nonbridging oxygen hole center (responsible for the 1.9 eV luminescence) and another undetermined defect (responsible for the 4.8 eV absorption) must be present in the glass before the 1.9 eV luminescence band can be excited by 4.8 eV photons.