Electron spin resonance measurement of radiation-induced defects and reactions in vitreous silica irradiated with ion beams

The electron spin resonance (ESR) measurement of irradiation defects and reactions in ion beam irradiated vitreous silica was performed. The spin densities of E′ centers, non-bridging oxygen hole centers (NBOHCs), and peroxy radicals (PORs) were measured as a function of the ion beam fluence and postirradiation isothermal annealing temperature. The spin densities of these centers were observed to saturate above the dpa value of 10−2. In isothermal annealing experiments, sequential reactions of the E′ centers with oxygen atoms to form the NBOHCs and PORs were observed to occur, and the rate constants of those reactions were determined. The activation energies were obtained to be about 0.4 eV for those reactions.