Direct vibrational excitation via charge exchange in symmetric ion–molecule collisions

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Abstract
Integral and differential cross sections for vibrational excitation in symmetric H+2(X 2Σ+g, v′0) + H2(X 1Σ+g, v″0) collisions have been determined for incident kinetic energies E (keV) in the range 0.01<E<2.0. A multistate impact parameter description of the collision was used. At low kinetic energies, the inclusion of a relatively small number of states in the wavefunction expansion of the system achieves converged cross sections while at high energies a large number of product states are needed. The inelastic channels in this symmetric system are strongly coupled to each other and to the energy resonant charge exchange channels. Differential cross sections for excitation of individual product channels have been computed as a function of scattering angle within the multistate impact parameter approach. Small angle scattering within several degrees is dominant with forward inelastic scattering becoming more pronounced as the ion kinetic energy is increased. Integral cross sections for individual channels and integral cross sections summed over all product channels are presented as a function of both ion kinetic energy and reactant internal energy.