State-selective double-electron capture processes for Ar2+-Ar collisions

Abstract

State-selective differential cross sections for double-electron capture by Ar2+ ions from Ar have been studied experimentally at laboratory impact energies of 2 and 4 keV and scattering angles between 0' and 2' using a time-of-flight spectroscopy technique. For small angles (0'-0.5'), the spectra indicated that the predominant process observed is due to capture into the Ar(3p6 1S) ground state. However, as the scattering angle is increased, other channels due to capture into the excited states of Ar successively start to contribute. These measurements show that the differential cross sections for double-electron capture are strongly peaked in the forward direction and display only weak oscillatory structure, in contrast to the marked structure generally expected when resonant electron capture can occur.