Stepwise contraction of the nf Rydberg shells in the 3d photoionization of multiply-charged xenon ions

TL;DR

This study investigates how the 3d Rydberg shells in multiply-charged xenon ions contract stepwise during photoionization, revealing the reordering of continuum states into Rydberg orbitals as ion charge increases.

Contribution

It provides experimental measurements and theoretical analysis of the evolution of 3d photoionization resonances in xenon ions with increasing charge state.

Findings

Resonance complexity increases with ion charge.

Reordering of continuum into Rydberg orbitals observed.

Experimental data matches relativistic atomic-structure calculations.

Abstract

Triple photoionization of Xe3+, Xe4+ and Xe5+ ions has been studied in the energy range 670-750 eV, including the 3d ionization threshold. The photon-ion merged-beam technique was used at a synchrotron light source to measure the absolute photoionization cross sections. These cross sections exhibit a progressively larger number of sharp resonances as the ion charge state is increased. This clearly visualizes the re-ordering of the $\epsilon$f continuum into a regular series of (bound) Rydberg orbitals as the ionic core becomes more attractive. The energies and strengths of the resonances are extracted from the experimental data and are further analyzed by relativistic atomic-structure calculations.