Initial-state-selected MNN Auger spectroscopy of atomic rubidium

The ${M}_{4,5}{N}_{2,3}{N}_{2,3}$ and ${M}_{4,5}{N}_{1}{N}_{2,3}$ Auger decay of atomic Rb have been studied by using photoelectron-Auger electron coincidence measurements that enable initial ionic state selected Auger spectroscopy. The Auger spectra in the present study are separated by the total angular momentum $j$ of the $3d$ hole and the orbital of the valence electron $n\ensuremath{\ell}$ after photoionization. It is shown that the technique allows isolating overlapping features and the study of otherwise unobservable spectral details, from which the presence of shake-down transitions during normal Auger decay is demonstrated experimentally. The technique allows also probing the effects of initial state parity and electron correlation in Auger electron spectroscopy. The observed spectral features are interpreted with theoretical predictions obtained from configuration interaction Dirac-Fock approach.