Single-electron capture processes in slow collisions of He2+ ions with O2, NH3, N2, and CO2

Abstract

Using the translational energy-gain spectroscopy technique, we have measured the energy-gain spectra and absolute total cross sections for single-electron capture (SEC) in collisions of He2+ ions with O2, NH3, N2, and CO2 at laboratory impact energies between 25 and 400eV/amu. The measured spectra for the He2+-N2 and CO2 collision systems show that the dominant reaction channel is due to dissociative transfer ionization (i.e., SEC accompanied by ionization of the molecular target ion). In the case of the He2+-NH3 collision system, nondissociative single-electron capture into n=2 states of He+ with production of NH3+ in the ground state is predominantly populated. These processes are observed to be the dominant reaction channels over the entire impact energy region studied and at laboratory scattering angles between 0°and 8°. The energy dependence of total cross sections for SEC are also measured and found to slowly increase with increasing impact energies. The measured cross sections are also compared with the available measurements and theoretical results based on the Demkov and Landau-Zener models. © 2005 The American Physical Society.