The role of dissociative electron capture in collisions of slow He2+ ions with CO

Translational energy spectroscopy (TES) has been used to study one-electron capture by 0.2-1 keV amu-1 He2+ ions in CO and identify, for the first time, the main excited product channels and determine cross sections for both dissociative and non-dissociative processes. Cross sections are shown to be strongly energy dependent over the energy range considered with the contribution from exothermic dissociative electron capture channels associated with He+(1s) formation accounting for about 99% of the total cross section at the lowest energy considered. Endothermic channels arising from non-dissociative one-electron capture have been observed which increase in relative importance as the impact energy increases. These lead to either He+(n=2) or He+(n=3) formation and various states of CO+ with some evidence of vibrational excitation. Of these, the He+(n=2)+CO+[X2Σ+] product channel (with an energy defect ΔE=-0.42 eV) is dominant and this accounts for about 40% of the total cross section at 1 keV amu-1. (author)