An approach to distinguish different channels for the population of fast heavy ion Rydberg states by beam-foil interaction

Abstract

Rydberg states of fast hydrogenic O7+ ions have been formed by passing 13-24 MeV oxygen ions of different initial charge states (qi=3,.,5) through a carbon foil. The Rydberg ions were detected by field ionization using RYDFISS, a method offering spatial separation of the Rydberg ions of interest from the rest of the ion beam. The yield of hydrogenic O7+ Rydberg states in the range 50<or=n<or=80 of main quantum numbers has been measured as a function of carbon foil thickness in the range between 5 and 36 mu g cm-2. By taking into account the development of charge fractions during foil passage, an analysis of the Rydberg yield in terms of a rate equation has been possible in order to extract Rydberg state production and destruction cross-sections from the measured data. At the energies investigated electron capture by the bare oxygen nucleus and bound-bound excitation within the O7+ system seem to contribute roughly equally to hydrogenic Rydberg state production.