State-selective differential cross sections of electron capture in 10 MeV Ar8+-He collisions

The single-electron capture processes in collisions of Ar8+ ions with He atoms have been studied at a collision velocity of 3.17 atomic units (au) through a state-selective measurement of differential cross sections. Cold-target recoil-ion momentum spectroscopy (COLTRIMS) has been employed to identify the final state of the captured electron and the momentum transfer between the collision partners. Relative differential cross sections for the capture to 3s, 3p n = 4, and n = 5 orbitals of Ar ions are obtained and are in qualitative agreement with a semiclassical close-coupling calculation using the molecular-state expansion method. The electron is dominantly captured to the n = 5 orbitals, which is in accordance with recent observations at lower velocities.