Doubly differential cross sections, in angle and energy, for state-selective single-electron capture from He and Ar by ${\mathrm{Ar}}^{\mathit{q}+}$ ions have been studied experimentally at laboratory impact energies between 25q and 100q eV (q=4 and 5, where q is the ion charge state) and scattering angles between 0° and 5°, by means of translational energy-gain spectroscopy. The translational energy-gain spectra show that only a few final states were selectively populated depending on the charge state of the projectile, ionization potential of the target, and weakly on the impact energy. A resonable description of the populated final states is described qualitatively in terms of the reaction windows, which are calculated using a multichannel Landau-Zener model. The general features of the differential cross sections are discussed in terms of a semiclassical curve-crossing model.

• Received 28 January 1993

DOI:https://doi.org/10.1103/PhysRevA.48.382