An interstitial hydroxyl radical (HO*) was generated in bulk amorphous SiO2 loaded with interstitial H2O molecules and exposed to F2 laser light (7.9eV, 157nm) at 77K. The laser light dissociated an O-H bond of interstitial H2O into a pair of H atoms (H0) and HO*. The resultant H0 disappeared below 150K, whereas HO* was detectable after thermal annealing at 200K. The electron paramagnetic resonance signal of the interstitial HO* recorded at 77K was similar to that found in amorphous ice; indicating that HO* was confined to an orthorhombic field by H-bonding, probably with adjacent H2O molecules, silanol (SiOH) groups, and bridging O atoms in the a-SiO2 network.

Interstitial OH Radicals in F2-Laser-Irradiated Bulk Amorphous SiO2. K.Kajihara, M.Hirano, L.Skuja, H.Hosono: Journal of Physical Chemistry B, 2006, 110[21], 10224-7