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 t ime, the main excited product channels and determine cross sections for bot h dissociative and non-dissociative processes. Cross sections are shown to be strongly energy dependent over the energy range considered with the cont ribution 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 nondisso ciative 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 vib rational excitation. Of these, the He+(n = 2) + Co+[X(2)Sigma (+)] product- channel (with an energy defect DeltaE = -0.42 eV) is dominant and this acco unts for about 40% of the total cross section at I keV amu(-1).