State-selective single- and double-electron capture in slow collisions of Ne4+ ions with CO2

Energy-gain spectra and absolute total cross-sections have been measured for single- and double-electron capture processes in collisions of Ne4+ ions with CO2 at laboratory impact energies between 60 and 1200 eV and scattering angles between 0 degrees and 6 degrees using a translational energy-gain technique. At 0 degrees scattering angle, the dominant peak corresponds to transfer excitation into the 3d excited state of Ne3+ from the ground state Ne4+ (2p(2) P-3) ion accompanied by excitation of the target product into the excited state ((2)Pi(u)) of CO2+, with contributions due to capture into the excited state 3d'. There is also some contribution from an unresolved reaction at about 11.5 eV, involving capture into the 3d state. The energy dependence of cross-sections for single-and double-electron capture are also measured and found to slowly increase with increasing impact energy. The data are compared with theoretical results based on the classical over the barrier and multi-channel Landau-Zener (MCLZ) models.