A CROSSED-BEAM STUDY OF ION-MOLECULE PROTON-TRANSFER DYNAMICS - VIBRATIONAL STATE-RESOLVED PRODUCTS IN THE O-+HF REACTION

We present the angular and kinetic energy distributions for the produc ts of the proton transfer reaction O-+HF-->OH+F- at a center of mass c ollision energy of 40.5 kJ mol-1 (0.42 eV). The angular distribution s hows clear forward-backward symmetry for the formation of products, in dicating that the reaction proceeds through a transient [OHF]- complex living several rotational periods. This is the first direct experimen tal evidence for the participation of a complex in this reaction. The product kinetic energy distributions show clear structure that we attr ibute to the formation of OH in vibrational states with quantum number s v' = 0, 1, and 2. Approximately 40% of the OH reaction products are formed in v' = 1. This value is consistent with drift tube studies at lower collision energies in which increasing reagent translational ene rgy transforms preferentially into product vibration. Such energy part itioning is consistent with the argument that mixed energy release in the Heavy + Light-Heavy mass combination is induced by the strong elec trostatic attraction of the reactants.