Electron correlation in Xe 4d Auger decay studied by slow photoelectron-Auger electron coincidence spectroscopy

Two different experimental methods, namely threshold electron-Auger electron coincidences and slow photoelectron-Auger electron coincidences are applied to investigate the Xe 4d Auger decay in the near-threshold region and reveal the essential role of electron correlation. The coincidences allow us to select the different channels for the 4d hole Auger decay which lead to different final states of the Xe²⁺ ion: 5s^-2( ¹S₀), 5s^-15p^-1(¹P ₁), 5p^-2(¹S₀), 5p^-2( ¹D₂), 5p^-2(³P_0,1) and 5p^-2(³P₂). Measurements of the threshold electrons with the first method reveal strong PCI distortion of electron spectra in all channels. Comparison with calculations carried out in the framework of the quantum-mechanical PCI model allows us to clarify the dynamics of threshold electron production. In the 5p^-2(¹S₀) channel, the main contribution comes from the PCI retardation of slow photoelectrons. In the 5p^-2(¹D₂) and 5p^-2( ³P) final state channels, additional processes of PCI recapture followed by valence multiplet decays play a role at and below the N₄ and N₅ thresholds. The slow photoelectron spectra measured by the second method reveal also a strong PCI distortion. Analysis within the framework of the eikonal model shows the influence of the Auger electron on the PCI distorted line shapes.