Rydberg levels population in the electron capture collision O6+ + He at low velocity

The population of levels with principal quantum numbers n largely in excess of the n = 3 (most populated level) in the single electron capture by O6+ from He (at 60 keV) is reported. The n = 4 population involves an ''electron promotion mechanism'' at small internuclear distances (R ≅ 2.5 ao). Our observations show population of levels up to n = 7 (Rydberg levels) leaving open the theoretical interpretation. (Author)