Coherence of nondegenerate states studied by auger electron-photoelectron coincidence experiments in Kr

The indirect double photoionization of Kr via the Kr+(3d(-1)(3/2,5/2)) states to the Kr2+(4s4p(5) (1)P(o)) final state has been studied by Auger electron-photoelectron angular resolved coincidence experiments. By tuning the incident photon energy, we succeeded in observing the coherence in the photoionization of two nondegenerate spin-orbit states. The observations have been described quantitatively by a model which accounts for the two pathways to the final state as well as for the indistinguishability of the two ejected electrons.