Hydrogen-related radiation defects in SiO2-based glasses

Spectroscopic properties of hydrogen atom trapped in an oxygen vacancy in SiO2 glass were studied. Samples were loaded with D2 and H2 gases to convert O vacancies to pairs of Si-D and Si-H groups, and subsequently irradiated by F2 laser in order to destroy some of these groups. Electron paramagnetic resonance, infrared absorption and visible/UV absorption spectra were measured. Proton hyperfine doublet with splitting of 1.05 mT was found in all H2-treated/irradiated samples. UV-bleaching treatment showed that this signal is independent of the other, well-known hydrogen-related signals in silica. The size of the hyperfine splitting corresponds to twice the 1H nuclear Zeeman splitting in applied magnetic field. The observed 1.05 mT doublet is tentatively attributed to the forbidden nuclear spin-flip transitions of proton trapped in an oxygen vacancy in silica. The allowed EPR transitions of this center are not resolved, possibly reflecting a variation in Si...H distance in oxygen vacancy with a trapped H atom