An analysis of the coincidence L 2–L 3M 4,5 Coster–Kronig preceded Auger decay spectra of Fe and Co and the related Auger–Auger electron coincidence spectroscopy (AACS) spectra

Abstract

It is shown by a many-body theory that when the delocalization time of the M 4,5 hole created in Fe (or Co) by the L 2–L 3V (V = M 4,5) Coster–Kronig (CK) decay is much shorter than the L 3-hole lifetime, the coincidence (or singles (noncoincidence)) L 2–L 3V–L 3–VV Auger electron spectroscopy (AES) main line of Fe (or Co) coincides in line shape and peak KE with the intrinsic singles L 3–VV one. This is also the case with the Auger decay following the L 1–L 2,3V CK decay or the L 1V (or L 2,3V) shakeup/off excitations. Thus, there is no line shape change with photon energy in the singles L 3–VV AES main line of Fe (or Co). In the light of the delocalization of the M 4,5 hole we analyzed the experimental singles and coincidence L 2,3–VV AES spectra of Fe and Co. The L 3 photoelectron background intensity beneath the singles L 2 photoelectron spectroscopy (PES) main line is found to be as large as the intrinsic singles L 2 PES main line one. The relative intensity of the coincidence CK preceded AES spectrum to the coincidence L 2–VV one of Fe increases by a factor of about 2.7 because of the Auger electrons collected in coincidence with the L 3 photoelectrons in the background beneath the singles L 2 PES main line. A subtraction of the background appropriate respectively for the coincidence AES (or PES) spectrum and the singles one is necessary to compare the two spectra. We discussed the prospect of determining by Auger–Auger electron coincidence spectroscopy (AACS) the charge transfer (CT) screening time or the delocalization time of the valence-hole in a doubly ionized state using as an internal clock the lifetime of a core hole in the same doubly ionized state. We analyzed the Mn M 2,3V–VVV and Mn M 2,3M 2,3–VVVV AACS spectra of MnO. The present analysis of the Mn M 2,3V–VVV AACS spectrum of MnO measured in coincidence with the singles Mn L 3–M 2,3V AES peak shows that the delocalization time of the valence hole in the doubly ionized state in MnO is shorter than the L 2,3-hole lifetime but longer than the M 2,3 one.