Theory of near-resonant charge exchange in atom-molecule collisions. Dissociative NRCE in the H2+ + Mg collision

TLDR: In this article, a theory of near-resonant charge exchange (NRCE) in ion + molecule or molecular ion + atom collisions is presented and applied to the H 2 + + Mg collision at medium energies.

Abstract: A theory of near-resonant charge exchange (NRCE) in ion + molecule or molecular ion + atom collisions is presented and applied to the H 2 + + Mg collision at medium energies. The NRCE probabilities are obtained within the impact-parameter method (IPM) using the short collision time approximation (sudden transition for the nuclear motion in the molecule). The relevant exchange interactions are determined in the framework of the asymptotic theory of NRCE, using elementary linear combinations of atomic orbitals (ELCAOs) to describe the molecular orbital of the active electron that is captured to/from the molecule. The corresponding formulas appear as mere superpositions of ion + atom-like results and provide the full dependence of the exchange interaction upon the internal coordinates of the triatomic collision system. The application to the H 2 + + Mg collision deals with the dissociative charge exchange into the b 3 Σ u + (direct dissociation), the a 3 Σ g + (radiative dissociation) and the c 3 Π u (predissociation) states of H 2− . The treatment incorporates explicitly the charge-induced-dipole (a-b, c) and charge-quadrupole interactions in the highly polarizable outgoing channels considered. Results of the IPM close-coupling calculations for a few energies and diatom orientations are presented and compared with experiment.