Non-Dissociative Single-Electron Capture Studied for O2^2+ Ions on Ar, N2 and He at 100 eV

Energy-gain spectra for single-electron capture by o2^2+ ions colliding with ar, he and n2 have been measured at an impact energy of 100 ev and 0° scattering angle by means of translational energy-gain spectroscopy. in o2^2+ - ar and n2 collisions, only one peak is observed at the energy-gain around 3.5 ev, which is correlated with nondissociative single-electron capture from ground state (x^1 σg^+) of o2^2+ ions into the a^2 πu state of o2^+. however, for the o2^2+ - he collision system, the dominant channels are due to capture into the ground state x^2 πg of o2^+ from w^3 δu, b^3 πg and b/^3 σu^- metastable states of the o2^2+, respectively. a reasonable description of the dominant final states is obtained qualitatively in terms of the reaction windows, which are calculated using the landau- zener (lz) model and the extended version of the classical over-the-barrier (ecob) model. differential cross sections for single-electron capture by 100 ev o2^2+ ions from ar have also been measured. the results are quantitatively explained by semi-classical model based on coulomb potential energy curves.