Imaging state-to-state reactive scattering in the Ar+ + H2 charge transfer reaction

TL;DR

This study uses advanced imaging techniques to analyze the detailed dynamics and internal excitations in the charge transfer reaction between Ar+ ions and H2 or D2 molecules, revealing new insights into product excitation and scattering behavior.

Contribution

It provides new experimental data on angular distributions and internal excitations in Ar+ + H2/D2 reactions, highlighting differences from previous findings and exploring vibrational and rotational state populations.

Findings

Product ions are highly internally excited.

Angular distributions show less back-scattering than previously observed.

Higher vibrational levels are populated in D2 reactions.

Abstract

The charge transfer reaction of Ar+ with H2 and D2 has been investigated in an experiment combining crossed beams with three-dimensional velocity map imaging. Angle-differential cross sections for two collision energies have been obtained for both neutral species. We find that the product ions are highly internally excited. In the reaction with H2 the spin-orbit excited Ar+ state's coupling to the 'resonant' vibrationally excited product H2+(v=2) dominates for both investigated energies, in line with previous investigations. The observed angular distributions, however, show significantly less back-scattering than was found previously. Furthermore, we discovered that the product ions are highly rotationally excited. In the case of Ar+ reacting with D2 the energetically closest lying vibrational levels are not strictly preferred and higher-lying vibrational levels are also populated. For both species the backward-scattered products show higher internal excitation.