GUIDED-ION BEAM STUDIES OF THE REACTIONS OF PROTONATED WATER CLUSTERS, H(H2O)(N)-4), WITH ACETONITRILE( (N=1)

Reactions of protonated water clusters, H(H2O)n+ (n = 1-4), with aceto nitrile are studied by using guided-ion beam mass spectrometry. Absolu te reaction cross sections are determined as a function of the collisi on energy from thermal energy to over 10 eV. Proton transfer, charge t ransfer, and dissociative proton transfer are the reactions seen for n = 1. For n = 2-4, proton transfer is accompanied by solvent transfer such that the dominant product at low collision energies is H(CH3CN)(H 2O)n-1+ in each case. At higher collision energies, additional water l igands are lost and the collision-induced dissociation products, H(H2O )n-m+ where m = 1 to n - 1, are also observed. The total reaction cros s sections are large and decrease slightly with the number of water mo lecules. The results indicate that energy transfer in these complexes is efficient and thus are consistent with reactions that proceed via h ydrogen-bonded intermediate complexes.