Diffusion and Reactions of Photoinduced Interstitial Oxygen Atoms in Amorphous SiO2 Impregnated with 18O-Labeled Interstitial Oxygen Molecules

Abstract

Both diffusion and reactions of interstitial oxygen atoms (O0) in amorphous SiO2 (a-SiO2) were examined using oxygen-excess a-SiO2 containing 18O-labeled interstitial oxygen molecules (O2) and exposed to F2 laser light (hν = 7.9 eV). Both the F2 laser photolysis of interstitial O2 at 77 K and subsequent heat treatment at ≳200 °C give rise to oxygen exchange between residual interstitial O2 and oxygen atoms in the a-SiO2 network, and these temperatures are far lower than the temperature at which conventional thermal network-interstitial oxygen exchange in unirradiated a-SiO2 occurs (≳700 °C). However, at the initial stage of the low-temperature F2 laser photolysis, an efficient formation of interstitial ozone molecules (quantum yield ≳0.06) via nearly exchange-free diffusion of photogenerated interstitial O0 is observed, and this reaction predominates over the network-interstitial oxygen exchange.