Reaction of H, D, and muonium atoms with I− in aqueous solution Original Research Article

Electron paramagnetic resonance free induction decay (FID) attenuation measurements are reported for the reaction of H and D atoms with I− in aqueous solution between 8 and 40°C. Muon spin resonance experiments are reported for reaction of the light muonium atom (Mu) with I− between 5 and 90°C. At 25°C, we obtain scavenging rate constaants of 5.3 × 107 M−1 s−1 for Mu, 2.8 × 108 M−1 s−1 for H, and 3.2 × 108 M−1 s−1 for D. The temperature coefficient for the reaction is slightly negative for all three isotopes; in terms of an Arrhenius law, the muonium rate constant has a −5.6 ± 1.8 kJ/mol activation energy. We consider three models attempting to explain the strange kinetic behavior, based on gas phase collision theory, electronic curve crossing, and transition state theory with tunneling and dynamic solvent effects.