Differential cross sections for single-electron capture by low-energy O22+ ions from Ne and O2

State-selective differential cross sections for single-electron capture processes in low-energy collisions of O22+ recoil ions with Ne and O2 at impact energy of 100 eV and scattering angles between 0° and 6° have been studied using a differential energy-gain spectrometer. In all of the collision systems studied here, contributions from processes commencing with long-lived metastable states in the incident O22+ ion beam are detected. The energy-gain spectra are interpreted qualitatively in terms of the reaction windows, which are calculated using the Landau-Zener model and the extended version of the classical over-the-barrier model.