Dynamics of double photoionization near the Ar 2p threshold investigated by threshold electron?Auger electron coincidence spectroscopy

Threshold electron–Auger electron coincidence spectroscopy measurements were carried out near the Ar 2p thresholds. Such a method allows us, for the first time, to observe the threshold electron yields associated with the selected final states of the Ar2+ ion: 3p4(1D2), 3p4(1S0), 3p4(3P) resulting from the 2p hole Auger decay. All the spectra reveal strong PCI distortion. Comparison with calculations carried out in the framework of a quantum-mechanical PCI model allows us to clarify the mechanisms and the dynamics of threshold electron production. In the 3p4(1D2) and 3p4(1S0) channels, contribution to the threshold electron yield comes essentially from the PCI retardation of slow photoelectrons. In the 3p4(3P) final state channel, an additional process of valence multiplet decay of the 3p4(1D2)6d state plays a role at and below the L2, L3 thresholds.