Laser-stimulated recombination spectroscopy for the study of long-range interactions in highly charged Rydberg ions.

The energy shifts of high-angular-momentum Rydberg states in berylliumlike O{sup 4+}, due to long-range interactions of the Rydberg electron with the ionic core, are measured by laser spectroscopy, using stimulated two-step recombination of free electrons with O{sup 5+} ions. The comparison of the accurate experimental results with theoretical shifts from the core polarization model and from {ital ab} {ital initio} atomic structure calculations shows considerable disagreement, demonstrating the need for an efficient method to include configuration interaction in a long-range interaction model.