Isotope Effects in the Reaction of H⁺(H₂O)₂/D⁺(D₂O)₂ with Acetone/Dimethylsulfoxide

Abstract

We investigated isotope effects in the reactions of protonated water dimer ions H⁺(H₂O)₂/D⁺(D₂O)₂ with acetone and dimethylsulfoxide (DMSO) using a guided ion beam apparatus. The reaction cross section, σ_r, of H⁺(H₂O)₂ with acetone was found to be slightly larger than that of D⁺(D₂O)₂ at low collision energies, <0.5 eV, where the ratio of the σ_r, was less than 1.5. The σ_r of H⁺(H₂O)₂ with DMSO was approximately twice as large as that of D⁺(D₂O)₂ with DMSO. Major reaction products were Y⁺X, where Y=H, D and X=acetone, DMSO. We examine two possible reaction processes, the proton transfer reaction via intermediate compounds and direct proton transfer.