Solvent-dependent rate constants of muonium atom reactions

The rates of reaction of muonium atoms with solutes, ionic and organic, were studied in solvents of wildly differing polarities (water, methanol, and hexane) and their rate constants were compared, where possible. In these reactions — which are those of a highly reactive atom, an isotope of hydrogen — it transpires that the reaction rates are higher in solvents in which the solute is more soluble and muonium diffuses faster. This study leads to various kinetic-solvent-effect ratios and to the observation of the reaction of muonium with free radicals being among the fastest reactions recorded so far between two neutral species in solution.Key words: muonium atoms, kinetic isotope effects, solvent-dependent rates, non-aqueous solvents, muon spin rotation technique.