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), 3p ⁴(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 3p ⁴(¹D₂) and 3p⁴(¹S ₀) channels, contribution to the threshold electron yield comes essentially from the PCI retardation of slow photoelectrons. In the 3p ⁴(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.