Mechanisms of reactions of H2O and NH3 molecules with ( Si-O)(3)Si and ( Si-O)(3)Si-O-center dot radicals on the silica surface

Spin traps, which are diamagnetic centers (=SiO)(2)Si, are used to register low-molecular radicals (OH)-O-., (NH2)-N-., and H formed by the reactions of H2O and NH3 molecules with the radicals (=Si-O)(3) Si-. and (=Si-O)(3)Si -O-. stabilized on the silica surface. The experimental data and the result s of quantum-chemical calculations for model systems are used to determine the mechanism and thermochemical characteristics of these reactions. A new paramagnetic center (=Si-O)(2)(SiNH2)-N-. was identified on the silica surf ace, and its radiospectroscopic characteristics are determined.