Kinetic Behavior of H and D Atoms in γ-Irradiated SiO2 as Studied by ESR Spectroscopy

The decay of hydrogen atoms, produced by γ irradiation of fused silica and quartz, was studied by ESR spectroscopy. The decay of H atoms in silica cannot be explained by a secondorder kinetics nor by a simple first-order kinetics. Also, the decay is not composed of several first-order processes with different activation energies. The data for the decay of H atoms can be described by a first-order kinetic equation with a timedependent rate constant of the form k(t) = Bt ^α?1, where B and α are constants. The decay kinetics of D atoms in deuterated fused silica and H atoms in a single crystal of quartz are also explained by use of the time-dependent rate constant. The apparent activation energies for the decay of H and D atoms in the silica are 15 to 16 kJ/mol and 14 to 15 kJ/mol, respectively. The decay rates for D and H atoms in the silica are similar.