Vibrationally state-selected reactions of ammonia ions. III. NH+3(v)+ND3 and ND+3(v)+NH3

Abstract

The role of vibrational excitation of the ν2 umbrella-bending mode of ND+3 (X̃,v=0 to 10) and NH+3 (X̃,v=0 to 9) on the reaction with NH3 and ND3 is examined over the 2 to 12 eV center-of-mass kinetic energy range. Isotopic substitution permits the investigation of charge transfer, proton/deuteron transfer, and neutral atom abstraction. The charge transfer channel is moderately enhanced by excitation of the ammonia ion ν2 vibrational mode. The proton/deuteron channel is suppressed by vibrational excitation of the ion at low kinetic energies. The hydrogen/deuterium atom abstraction channels show nearly a factor of 6 vibrational enhancement relative to NH+3 (v=0). The ion vibrational and translational energy play inequivalent roles in the reactions, indicating that nonstatistical factors are important in the transition from reactant to product channels. A simple dynamical model is offered to explain both the proton/deuteron transfer and the neutral atom abstraction reactions; it is based on the argument that vibrational motion along the particle transfer coordinate promotes reaction while vibrational motion perpendicular to the transfer coordinate hinders reaction.