Reactions of protonated water clusters H+(H2O)n (n=1–6) with dimethylsulfoxide in a guided ion beam apparatus

Reaction cross sections for the reactions of protonated water clusters, H+(H2O)n (n=1–6) with dimethylsulfoxide (DMSO) were measured at the collision energy of 0.1 eV. The cross section at n=2, which was found to be twice as large as that at n=4, showed a possibility of direct proton transfer process. The proton is likely to transfer directly from H+(H2O)2 to DMSO without forming an intermediate complex because of the larger proton affinity of DMSO than that of water dimer.