Correlation of preexisting diamagnetic defect centers with induced paramagnetic defect centers by ultraviolet or vacuum-ultraviolet photons in high-purity silica glasses

Electron-spin-resonance (ESR) and vacuum-ultraviolet (vuv) absorption measurements were performed on a series of high-purity silica glasses exposed to 6.4-eV photons, 7.9-eV photons from excimer lasers, and to γ rays. The concentration of defect centers varies from ${10}^{14}$ to ${10}^{16}$ ${\mathrm{cm}}^{\mathrm{-}3}$ depending on the method of material fabrication and photon energy of the irradiating lasers. Variation of the defect species with both the incident-photon energy and manufacturing condition is observed by ESR measurements. E’ centers (°Si⋅) are observed in all types of silicas. Nonbridging-oxygen hole centers (NBOHC’s °Si-O⋅) in high-OH silica ([OH]≊1000 ppm) and peroxy radicals (PR’s, °Si-O-O⋅) in oxygen-surplus silica ([OH]E’ centers, NBOHC’s, and PR’s.