State-selective single-electron capture in very slow collisions of Arq+ (q = 4-8) ions with neon

Abstract

State-selective differential cross sections for single-electron capture processes in very slow collisions of Arq+ (q = 4–6) ions with neon (Ne) have been studied experimentally at laboratory impact energies between 0.4 and 4 qeV/amu and scattering angles between 0 ° and 8 ° by means of the translational energy-gain spectroscopy technique. The translational energy spectra show that the dominant reaction channels are due to capture into excited states of the projectile product Ar(q−1)+. However, at very low energies, other channels due to transfer excitation processes are found to open at large scattering angles. The energy-gain spectra are interpreted qualitatively in terms of the reaction windows, which are calculated using the single-crossing Landau-Zener model and the extended version of the classical over-the-barrier model. The energy dependence of cross sections for single-electron capture by Arq+ (q = 4–8) ions from Ne are also measured and found to be nearly constant with changing impact energy, but increase with an increase in the projectile charge state. The data are also compared with available measurements and theoretical calculations. Copyright © 1999 John Wiley & Sons, Ltd.