Itabashi-ku, Japan
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Ohno M.,Quantum Science Research
Chemical Physics | Year: 2012

A pair of Auger electrons generated, respectively, by creation and annihilation of the same multiple-hole state can be collected in coincidence by Auger Auger-electron coincidence spectroscopy (AAECS). In the present paper a many-body theory of AAECS spectra generated by Auger cascade decays in which the lifetime of a core-hole acts as an internal clock for the screening mechanism is formulated by treating photoelectrons and Auger electrons on the same footing. The unexploited basic spectral features of AAECS spectra of solids are elucidated by the present theory to show how the core-hole screening (delocalization of a valence hole) will affect the coincidence spectral lineshape. © 2011 Elsevier B.V. All rights reserved.


We calculated the Ti M 2,3-VV Auger-photoelectron coincidence spectroscopy spectrum of TiO 2(1 1 0) by a many-body theory. The spectral main line is governed by the DOS of the two O 2p holes living longer than the Ti cd 2L 2〉 → L 2〉 super Coster-Kronig (sCK) decay. The two O 2p holes are created by the charge transfer core-hole screening at the Ti atomic site. Here c and L are the Ti 3p hole and the ligand O 2p hole, respectively. Analysis of the spectrum shows that the two (or three) CT O 2p holes in the π bonding states are localized, whereas those in the σ bonding states are delocalized. The three localized CT O 2p (π) holes in cd 3L 3〉 in Ti M 2,3 main line (or satellite) of TiO 2(1 1 0) live longer than the Ti cd 3L 3〉 → d 1L 3〉 sCK decay so that the Coulomb repulsion from the surrounding Ti ions gives the O + ion desorption from the surface. © 2011 Elsevier B.V. All rights reserved.


No clear resonance is present in the resonant valence band photoemission spectrum of a Mn 6 (S = 4) single molecule magnet grafted on Au (1 1 1) for photon energy at the L 2 resonance edge. This is due to the L 2-hole's dominant decay by the L 2-L 3V Coster-Kronig (CK) decay. The excess energy of the photon at which the Mn resonant Raman scattering regime transits to the normal Mn Auger-decay regime in MnO depends on the Mn Auger-decay channels. This is because of the localization and delocalization of two holes in the Auger final states. The Mn resonant Auger-electron spectroscopy spectra of MnO are analyzed. © 2012 Elsevier B.V. All rights reserved.


Ohno M.,Quantum Science Research
Chemical Physics | Year: 2012

The Auger-photoelectron coincidence spectroscopy (APECS) and Auger Auger-electron coincidence spectroscopy (AAECS) spectral behaviors of Auger cascade decay are discussed by a many-body theory. There is a significant difference in the coincidence intensity distribution in a two-dimensional map according to whether a pair of coincidence electrons are generated, respectively, by creation and annihilation of the same n-hole state (n≥1). The difference manifests as a line narrowing and a peak KE shift of the coincidence spectrum compared to the singles (noncoincidence) one. We discussed the inherent mechanism of APECS (AAECS), which causes the difference. © 2012 Elsevier B.V. All rights reserved.


Ohno M.,Quantum Science Research
Journal of Electron Spectroscopy and Related Phenomena | Year: 2010

Abstract: The Ta bulk N7-level of TaC(1 1 1) decays either by the on-site Auger decay or by the interatomic off-site one. By the interatomic off-site Auger decay the subsurface core-hole is filled by a subsurface valence electron, and the excess energy is dissipated by the excitation of the neighboring surface N7 electron to an unoccupied state, just above the Fermi level. The interatomic Auger decay is followed by the surface on-site Auger decay [R.A. Bartynski, S. Yang, S.L. Hulbert, C.-C. Kao, M. Weinert, D.M. Zehner, Phys. Rev. Lett. 68 (1992) 2247]. We showed by a many-body theory that the Ta N7-VV Auger-electron spectroscopy (AES) spectrum of TaC(1 1 1) produced by the surface Auger decay via the interatomic Auger decay, measured in coincidence with the bulk core-level photoemission coincides in both line shape and peak kinetic energy (KE) with the singles (noncoincidence) Ta N 7-VV AES one produced by the surface Auger decay. This explains why Bartynski et al. [Phys. Rev. Lett. 68 (1992) 2247] could describe the coincidence Ta N7-VV AES spectrum of TaC(1 1 1) produced by the surface Auger decay via the interatomic Auger decay by a self-convolution of the valence band density of states (SCDOS) from the first atomic layer. © 2010 Elsevier B.V. All rights reserved.


Ohno M.,Quantum Science Research
Journal of Electron Spectroscopy and Related Phenomena | Year: 2011

The M4,5-N2,3N2,3 Auger-electron spectroscopy (AES) spectrum of atomic Sn is calculated by an ab initio atomic diagramatic perturbation theory, i.e., the extended frozen core random phase approximation with exchange (RPAE). The AES spectrum is entirely smeared out and in good agreement with the experimental M4,5-N2,3N 2,3 AES spectrum of metallic Sn showing no discernible structure. It shows the complete breakdown of the quasi-particle picture of the two N 2,3 holes by the N2,3N2,3-N4,5N 4,5N4,5N4,5 and N2,3N 2,3-N2,3N4,5N4,5 super Coster-Kronig (sCK) transitions. The present theory shows that one should be able to detect the missing M4,5-N2,3N2,3 AES lines by measuring the M4,5 photoelectron spectroscopy (PES) spectrum in coincidence with the M4,5-N2,3N2,3 Auger decay. The lifetime width of the two N2,3 holes is much larger than the effective Coulomb hole-hole interaction energy U between the two N2,3 holes so that the multiplet coupling between the two N2,3 holes breaks down. This is analogous to the case when U between two holes created in valence band states is much smaller (or larger) than the bandwidth, the two holes are delocalized (or localized). © 2011 Elsevier B.V. All rights reserved.


Ohno M.,Quantum Science Research
Journal of Electron Spectroscopy and Related Phenomena | Year: 2011

The Si 2p photoelectron spectroscopy (PES) main line of Si(1 0 0) surface measured in coincidence with the singles (noncoincidence) Si L2,3-VV Auger-electron spectroscopy (AES) elastic peak is calculated. The agreement with the experiment is good. The present work is the first many-body calculation of the experimental coincidence PES spectrum of solid surface. The narrowing of the coincidence Si 2p PES main line compared to the singles one is due to the mechanism inherent in the coincidence PES. The inherent mechanism is explained by a many-body theory by which photoemission and Auger-electron emission are treated on the same footing. © 2011 Elsevier B.V. All rights reserved.


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(1 1 0) 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(1 1 0) 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. © 2010 Elsevier B.V. All rights reserved.


The L3 photoelectron spectroscopy (PES) spectrum of Co measured in coincidence with the L3-VV Auger-electron spectroscopy (AES) peak is analyzed by a many-body theory. The spectrum provides hard evidence that the L3 PES shakeup/off satellite relaxes fully to the L3 PES main line prior to the L3-hole decay. This is in accord with the experimental finding that except for a very weak AES satellite, there is no appreciable line shape change between the singles (noncoincidence) L 3-VV AES spectrum of Co measured just above the L3 PES main-line ionization edge and the one far above the L1 -level ionization edge. The delocalization time of the valence hole created together with the core-hole in the atomic L shell in Co is shorter than the core-hole lifetime. © 2013 Elsevier B.V.

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