Recent results in muonium solution kinetics

Abstract

Using Muonium Spin Rotation (MSR) techniques the aqueous solution kinetics of several muonium addition reactions and spin conversion interactions have been studied. The addition reactions show both diffusion and activation-controlled reaction rates with isotope effects between 1 and 3 for diffusion-control and between 7 and 31 for activation-control reactions. Barrier energies are typically ≈15 kJ/mole and ≈30 kJ/mole, respectively, for these processes in water. Spin-conversion interactions involving Ni_(aq ⁺² and Ni(cyclam)⁺² complexes showed that spin-conversion of “triplet” Mu by a paramagnetic solute occurs at or near the diffusion-controlled limit while the chemical reaction with the diamagnetic configuration of Ni(cyclam)⁺² occured some 100 times slower at k_M ⩽ 5×10⁸M⁻¹s⁻¹.