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Ion desorption from condensed F3SiCD2CH2Si(CH3)3 induced by Si-2p core-level ionizations of the F3Si— and the —Si(CH3)3 sites (Si[F] and Si[Me]) was investigated using photoelectron photoion coincidence (PEPICO) spectroscopy, Auger photoelectron coincidence spectroscopy (APECS) and Auger electron photoion coincidence (AEPICO) spectroscopy. A Si-2p-F+ PEPICO peak appeared selectively in the Si[F]-2p region. Si-2p-H+ PEPICO peaks were, on the other hand, observed in both the Si[Me]- and Si[F]-2p regions. The structure of the Si-L23VV-Si[F]-2p Auger photoelectron coincidence spectrum (APECS) was quite different from that of the Si-L23VV-Si[Me]-2p APECS. Ab initio molecular orbital calculations qualitatively reproduced the measured APECSs. The peak positions in the Si-L23VV-F+ AEPICO spectrum were in good agreement with those in the Si-L23VV-Si[F]-2p APECS. The Si-L23VV-H+ AEPICO spectrum, on the other hand, showed no characteristic peaks. Based on these results we have concluded that the site-specific F+ desorption is stimulated by Si[F]-L23VV Auger processes, and that both the Si[Me]- and Si[F]-L23VV Auger decays are responsible for the non-site-specific H+ desorption. [ABSTRACT FROM AUTHOR]

Abstract: Using the charge transfer (CT) core-hole screening model we analyzed the photoelectron–photoion coincidence spectroscopy (PEPICS) spectra of the O+ ion desorption from TiO2(110) surface measured in coincidence with the Ti or O core-electron photoemission. The present theory predicts well the ratio of the PEPICS spectral intensity measured in coincidence with the Ti core photoelectron spectroscopy (PES) satellite to that with the Ti core PES main line. In contrast to the Knotek and Feibelman (KF) mechanism the three localized O 2p holes created by CT Ti core-hole screening outlast the desorption so that the O+ ion desorbs from TiO2(110) surface upon the Ti core-electron ionization. The O 1s PES satellite creates three localized O holes by the O KV-L1VV spectator Auger decay, while the O 1s PES main line creates three localized O holes by the O K-VVV and K-L1VV Auger shakeup decay. As the Auger shakeup decay is very small compared to the spectator Auger decay, the O+ ion desorption yield in coincidence with the O 1s PES shakeup satellite is much enhanced compared to that with the O 1s PES main line. [Copyright &y& Elsevier]

• Strong correlation energies are measured in Auger spectra from Fe ultra-thin films. • Coulomb and exchange interactions are estimated for eg and t 2 g states and both spins. • Exchange coupling is due only to the more itinerant t 2 g electrons. • e g electrons undergo a stronger localization when Fe is coupled to the CoO substrate. • Fe bonded to O does not play relevant role in the magnetic properties at the interface. Angle resolved-Auger photoelectron coincidence spectroscopy (AR-APECS) has been exploited to investigate the role that electron correlation plays in the exchange-coupling at the ferromagnetic/antiferromagnetic interface of a Fe/CoO bilayer grown on Ag(001). The effective correlation energy U eff , usually employed to assess the energy distribution of core-valence-valence Auger spectra, has been experimentally determined for each possible combination of the orbital (e g or t 2 g) and the spin (majority or minority) of the two valence electrons involved in the Auger decay. Coulomb and exchange interactions have been identified and compared with the result obtained on the Fe/Ag system. The presented analysis reveals in the Fe/CoO interface an enhancement of the Coulomb interaction for the e g orbital and of the exchange interaction for the t 2 g orbital with respect to the Fe/Ag case, that can be associated with the stronger electron confinement and to the exchange coupling between the two layers, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Topmost-surface-sensitive Si-2p photoelectron spectra of a clean Si(100)-2×1 surface have been measured using Si-2p photoelectron Si-L23VV Auger coincidence spectroscopy (Si-2p–Si-L23VV PEACS). The escape depth of the PEACS electrons is estimated to be ∼1.2Å. The results support the assignments of the Si up-atoms, the Si down-atoms, the Si 2nd-layer, and the Si bulk proposed in previous researches. The Si-2p component with a binding energy of −0.23eV relative to the bulk Si-2p3/2 peak, is shown to originate mainly from the topmost surface. Site selectivity of PEACS is indicated to be achieved to some degree by carefully selecting the kinetic energy of the Auger electrons. Since PEACS can be applied to any surface, the present study opens a new approach to identify PES components. [Copyright &y& Elsevier]