State-selective charge transfer studies relevant to solar wind-comet interactions

We report relative experimental and absolute theoretical n-state-selective, nondissociative, single-electron capture cross sections for a number of collision systems typical of the solar wind-comet interactions. The experimental measurements were carried out using the technique of cold-target recoil-ion momentum spectroscopy and involved the N⁷⁺ and O⁷⁺ projectile ions and, for the first time, the H₂O, CO₂, and CO molecular targets, as well as the He atomic target. The theoretical calculations were performed using the classical trajectory Monte Carlo (CTMC), the Landau-Zener (LZ), and the classical over-the-barrier (COB) models. The models, with CTMC favored, agree reasonably well with the measurements and can be used in the near term to aid in the modeling of cometary X-ray and EUV emission. The pathways through which multiple-electron capture processes contribute to the cometary X-ray and EUV emission are also discussed.