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

State-selective differential cross sections for single-electron capture pro cesses in very slow collisions of Arq+ (q = 4-6) ions with neon (Ne) have b een studied experimentally at laboratory impact energies between 0.4 and 4 qeV/amu and scattering angles between 0 degrees and 8 degrees by means of t he translational energy-gain spectroscopy technique. The translational ener gy 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 en ergies, other channels due to transfer excitation processes are found to op en at large scattering angles. The energy-gain spectra are interpreted qual itatively in terms of the reaction windows, which are calculated using the single-crossing Landau-Zener model and the extended version of the classica l over-the-barrier model, The energy dependence of cross sections for singl e-electron capture by Arq+ (q = 4-8) ions from Ne are also measured and fou nd to be nearly constant with changing impact energy, but increase with an Increase In the projectile charge state. The data are also compared with av ailable measurements and theoretical calculations. Copyright (C) 1999 John Wiley & Sons, Ltd.