Fluorescence-mediated postcollision interaction in x-ray photoionization of the Xe $K$ edge

Postcollision interaction (PCI) in near-threshold photoionization of the $K$ shell of atomic Xe is investigated with hard-x-ray synchrotron radiation. Applying Auger electron spectroscopy, line-shape distortion is monitored in the $K\text{−}{L}_2\to L_2{M}_{4,5}{M}_{4,5}$ decay channel, where the initial $K\text{−}{L}_2$ ($K{\alpha }_2$) x-ray-emission step mediates the emission of the two continuum electrons. The $K$-edge result is compared to similar data obtained on direct $L_2{M}_{4,5}{M}_{4,5}$ decay at the $L_2$ edge without x-ray-emission. It is found that the evolution of the PCI shift with excess photon energy is very similar at both edges, but a subtle decrease in the PCI shift is observable at the $K$ edge due to the effect of the ultrafast x-ray emission step delaying the PCI energy exchange by a few attoseconds.