A crossed beam study of ion–molecule proton transfer dynamics: Vibrational state-resolved products in the O−+HF reaction

Abstract

We present the angular and kinetic energy distributions for the products of the proton transfer reaction O−+HF→OH+F− at a center of mass collision energy of 40.5 kJ mol−1 (0.42 eV). The angular distribution shows clear forward–backward symmetry for the formation of products, indicating that the reaction proceeds through a transient [OHF]− complex living several rotational periods. This is the first direct experimental evidence for the participation of a complex in this reaction. The product kinetic energy distributions show clear structure that we attribute to the formation of OH in vibrational states with quantum numbers 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 energy transforms preferentially into product vibration. Such energy partitioning is consistent with the argument that mixed energy release in the Heavy+Light–Heavy mass combination is induced by the strong electrostatic attraction of the reactants.