The Reaction of Muonium with Hydrogen Peroxide in Aqueous Solution

Rate constants for the reactions of muonium (Mu) (the ultralight isotope of the hydrogen atom) with H2O2 in H2O and D2O2 in D2O have been determined at various temperatures and pH (pD) values. The data are consistent with the three reactions: Mu+H2O2 & RARR;k1Mproducts ${{\rm{Mu}} + {\rm{H}}_2 {\rm{O}}_2 \mathop \rightarrow \limits <^>{{k_{1{\rm{M}}} }}_{} {\rm{products}}}$, Mu+HO2-& RARR;k2Mproducts ${{\rm{Mu}} + {\rm{HO}}_2<^> - \mathop \rightarrow \limits <^>{{k_{2{\rm{M}}} }}_{} {\rm{products}}}$, Mu+O-& RARR;k3Mproducts ${{\rm{Mu}} + {\rm{O}}<^> - \mathop \rightarrow \limits <^>{{k_{3{\rm{M}}} }}_{} {\rm{products}}}$ and the equivalent for the deuterated entities. A significant positive H/D isotope effect was found for the undissociated peroxide, while for the anions the effect was negligible or slightly in the opposite direction. In addition, for concentrated solutions of peroxide a study of the muon spin polarization as a function of applied transverse magnetic field yielded results consistent with the rate constants determined from the direct decay measurements, and indicated that the reaction products are diamagnetic, most likely MuH and MuOH, i. e., no muoniated radical products are formed. These results are potentially relevant for management of the radiolysis products in nuclear industry. Experimental data on muonium kinetics in water greatly expands the set of experimental data on kinetic isotope effects in the reactions of H atoms with H2O2 and its conjugate base HOO-.image

Automated summary

Rate constants for the reactions of muonium (Mu) with H2O2 and D2O2 have been determined at different temperatures and pH values. The results show that Mu reacts with H2O2, HO2-, and O- to form MuH and MuOH. The isotope effect is observed for the undissociated peroxide, while for the anions the effect is negligible or slightly in the opposite direction. These findings have potential significance for the management of radiolysis products in the nuclear industry.