Influence of electronic exchange on single and multiple processes in collisions between bare ions and noble-gas atoms

The time-dependent many-electron problem encountered in the theory of energetic ion-atom collisions can be approached systematically within an effective single-particle picture, based, e.g., on the time-dependent density functional theory. In the present contribution we investigate ionization and electron loss from the target for the collision systems p, p̄, He²⁺+Ne, and p+Ar in the energy range 10 keV/amu--1 MeV/amu. The results presented are based on a static approximation to the exchange-correlation contribution of the effective potential. The corresponding time-dependent single-particle equations are solved with the continuum distorted-wave with eikonal initial-state approximation and the basis generator method, a coupled-channel approach in terms of structurally adapted basis functions. We demonstrate that in either case the results depend strongly on the explicit form of the local static exchange potential. An orbital-dependent analysis of electron removal in He²⁺+Ne collisions shows that the quality of the exchange potential is decisive for the suppression of artificial reaction channels.