Electron swapping between the two nuclear centers in electron transfer in HCI-atom collisions

I. BLANK; S. OTRANTO; R. E. OLSON; R. HOEKSTRA

Heidelberg

Conferencia; 16th International Conference on the Physics of Highly Charged Ions; 2012

We present an experimental and theoretical study of state selective and angular differential cross sections of single electron transfer in collisions of N5+, O6+ and Ne8+ with ground state Na(3s). Experiments were performed using recoil-ion momentum spectroscopy in combination with a magneto-optically cooled Na atom target in the collision energy range from 1 to 8 keV/amu. The results are compared with three-body classical-trajectory Monte Carlo (CTMC) calculations. CTMC is well suited to describe these systems since HCI-atom collision lead to population of very high lying final states. While the total cross sections show no sign of structure as a function of the collision energy, a weak oscillatory pattern appears in the n-shell selective cross sections for capture into the higher final states. Our theoretical analysis indicates that this feature is linked to the number of times the active electron is swapped, i.e. crosses the potential energy saddle, between the two nuclear centers during the collision process. The oscillatory structure is more apparent in the experimental and theoretical angular differential cross sections for capture into higher final states and is very sensitive on the impact energy. While differential cross sections into lower final states show no obvious sign of oscillations, we show that also in these cases the spectra consist of contributions of different number of swaps, however the features are overlapping. Since we find evidence for electron back and forth swapping in all systems under study we argue that this effect is a general feature of low-energy collisions of highly charged ions with atoms.