The annihilation of mobile protons in thinSiO2films by capture of ultraviolet-excited electrons has been analyzed for temperatures between 77 and 500 K. We observe a strong increase in proton annihilation with increasing temperature, and derive an activation energy for electron capture of about 0.2 eV. Based on quantum chemical[(OH)3Si]2&sngbnd;O&sngbnd;H+cluster calculations, we suggest photoexcitation of electrons from excited vibrational states of the ground electronic (valence band) state to a nearby excited electronic (SiO2gap) state. It is argued that the latter excitation can result inH0formation at elevated temperatures. ©1998 American Institute of Physics.