Many-body effect in Auger-electron spectra by participant Auger transitions of a core-hole satellite

Abstract

A discrete two-hole one-particle (2hlp) shakeup/down state can decay either by spectator Auger transitions or by participant Auger transitions. The 2hlp state created by the participant Auger transition of the 2hlp shakeup/down state can be the same as the one created by the Auger transition of the 1h state. The participant Auger transition by which the electron excited by the shakeup/down fills the core hole, can be dominant. If this is so, when the two discrete core-hole states couple to the same continuum and their separation energy is smaller than or comparable to the core-hole lifetime width, there is a possibility of an interference between the Auger transition of the 1h state and the participant Auger transition of the 2hlp state. The screening of the Auger electron emission of the 1h state via the participant Auger transition of the 2hlp state leads to a pronounced interference in the Auger-electron spectroscopy (AES) spectrum. Because the screening function behaves like a Fano resonance. As the function is critically energy dependent, the photoelectron spectroscopy (PES) line peaks do not coincide with the AES ones, when the latter ones are shifted by the 2h final-state energy. In such a case, the PES line peak measured in coincidence with the AES one is shifted from the noncoincidence PES one. When the photoelectron is collected in coincidence with the Auger electron (or X-ray fluorescence) for a selected decay channel, i.e., when the doubly differential photoionization cross section of the photoelectron and the Auger electron (or X-ray fluorescence) being emitted and collected in coincidence is integrated over the Auger-electron kinetic energies (or X-ray fluorescence energies) of the selected decay channel and summed for the final states of the selected decay channel, the photoelectron spectrum is the noncoincidence (singles) photoelectron spectrum weighted by the branching ratio of the partial decay rate of the selected decay channel so that we can extract the screening function by comparing the coincidence photoelectron spectrum with the singles (noncoincidence) photoelectron one.