Strongly perturbed state-selective charge exchange between slow Ar^{8+} and He

We report an experimental and theoretical study of state-selective charge exchange processes in Ar^{8+} on He collisions at 1 and 3 keV/amu, benchmarking the fundamental electron capture dynamics under strong perturbations. The quantum-state selectivity has been experimentally resolved for one 1s electron of He capture into 4s, 4p, 4d+4f, and 5s states of Ar^{7+} ion along with the corresponding scattering angle differential cross sections. By comparing to theoretical calculations with a two-active-electron semiclassical asymptotic-state close-coupling approach, we are able to verify the important role of electronic correlations during the collisions and that the impact parameter sensitive transition probability significantly mediates the state-selective specifics.