STATE-SELECTIVE DIFFERENTIAL CROSS-SECTIONS OF ELECTRON-CAPTURE IN 10MEV 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 unit s (au) through a state-selective measurement of differential cross sec tions. Cold-target recoil-ion momentum spectroscopy (COLTRIMS) has bee n employed to identify the final state of the captured electron and th e momentum transfer between the collision partners. Relative different ial 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 semic lassical close-coupling calculation using the molecular-state expansio n method. The electron is dominantly captured to the n = 5 orbitals, w hich is in accordance with recent observations at lower velocities.