Final-charge-state-dependence in the production of foil-excited heavy Rydberg atoms

Studies of foil-excited fast (MeV/amu) heavy ions have demonstrated large yields of high Rydberg atoms formed in such beams. Further experiments have suggested a strong target-thickness dependence of the yields of such atoms. In an effort to better understand these results, we have measured the yields of Rydberg atoms (nproportional100-200) in foil-excited 32S ions at an incident energy of 125 MeV. The Rydberg atoms were field-ionized in a longitudinal electric field (proportional5 kV/cm) and the detached electrons were detected in coincidence with the remaining charge-state-analyzed ionic cores. The experiments show that while the yields of foil-excited Rydberg atoms depend strongly on the incident ionic charge state and the target thickness, they are relatively insensitive to the final charge states. These results show the importance of bulk processes over surface effects. (orig.)