Super Coster-Kronig Research Articles

Influence of ion irradiation on the surface electronic structure of epitaxial lanthanum nickelate films

We studied the influence of Ag15+ (200 MeV) ion irradiation on the surface electronic structure of an epitaxial LaNiO3 films on a (100) oriented LaAlO3 substrate, using surface sensitive La (4d to 4f) and Ni (3p to 3d) photoemission transitions in the pristine, highest (1012 ions/cm2), medium (5 × 1011 ions/cm2), and lowest (1011 ions/cm2) ion-doses of irradiation. The Super-Coster Kronig induced slight enhancement in the spectral features around ∼115–116 eV photon energy for La (4d to 4f) transitions were observed, with absence of such enhancement for Ni (3p to 3d) transitions in the pristine and irradiated samples. Moreover, an alteration in the constant initial state (CIS) spectra for La (4d to 4f) transitions and presence of a surface states close to the Fermi level in the valence band spectra for Ni (3p to 3d) transitions, with a different ion-doses found to be associated with the oxygen vacancies. Interestingly for Ni (3p to 3d) transition spectra, the density of states (DOS) at the Fermi Level was found to increase orderly with the irradiation dose, and a systematic correlation between the DOS at Fermi level and the surface states was found in the pristine and irradiated samples. For the highest dose sample, the surface states lie above the Fermi level has highest DOS at the Fermi level, which is due to upward shift of the surface states towards the Fermi level with an increase in the irradiation dose.

Coster-Kronig and super Coster-Kronig transitions from the Xe 4s core-hole state.

Coster-Kronig and super Coster-Kronig transitions from the Xe 4s core-hole state are investigated by coincidence detection of all the emitted electrons and product ions. The branching ratios of the transitions are determined by analyzing the coincidence data and comparing them to calculations. Subsequent decay pathways following these first-step Auger decays are also clarified.

A Review, Tabulation, and Parameterization of M-Series X-Ray Production Cross Sections for Proton and Helium Ion Impact

In the present work, the experimental total and line resolved M-series x-ray production cross sections (XRPCSs) for different elements with Z = 59–92 for 0.05–39.34 MeV proton and 0.2–6.0 MeV He ion (3He/4He) impact reported by different research groups until December 2020 have been compiled in tabular form. A status of different physical parameters, namely, the ionization cross sections, x-ray emission rates, fluorescence yields, and Coster–Kronig and super Coster–Kronig yields, required to calculate the theoretical M-series XRPCSs have been reviewed. The tabulated experimental total M-series XRPCSs for different elements are found to exhibit universal scaling similar to that shown by the theoretical cross sections. These tabulated experimental cross sections for different elements have been parameterized in order to provide empirical cross sections for use in different applications.

Super-Coster-Kronig decay of Kr 3p core-hole states studied by multielectron coincidence spectroscopy

Super Coster-Kronig (SCK) decay following Kr $3p$ photoionization has been investigated using a multielectron coincidence method. It is found that the SCK pathway occupies 23% of the $3{p}_{1/2}$ decay and only 2.5% of the $3{p}_{3/2}$ decay. The significant difference between the two $3p$ spin-orbit levels mainly results from the difference in energetics: almost all SCK transitions are energetically allowed in the $3{p}_{1/2}$ decay but only SCK transitions to the $^{3}F$ levels of $3{d}^{\ensuremath{-}2}$ are possible in the $3{p}_{3/2}$ decay. Subsequent decay processes from the SCK-final $3{d}^{\ensuremath{-}2}$ states are investigated, where a maximum of fivefold electron coincidences are analyzed.

Experimental and theoretical study of 3 p photoionization and subsequent Auger decay in atomic chromium

Abstract 3p photoionization and subsequent low kinetic energy Coster–Kronig and super Coster–Kronig Auger decay have been studied in atomic chromium. The binding energies, line widths, and relative intensities for the transitions seen in the synchrotron radiation excited 3p photoelectron spectrum are determined. The high resolution M 2 , 3 M 4 , 5 M 4 , 5 and M 2 , 3 M 4 , 5 N 1 Auger electron spectra following the electron impact excited 3p ionization are presented and the kinetic energies, relative intensities, and identifications are given for the main lines. The experimental findings are compared with the theoretical predictions obtained from Hartree–Fock and multiconfiguration Dirac–Fock approaches.

Measurement of the O2O3O4 and O3O4O5 super Coster–Kronig rates in tungsten via asymmetric diffraction spectrometry

The tungsten Lγ transitions between 11 and 12 keV and Kα transitions from 57 to 60 keV were produced by a laboratory electron-bombarded x-ray source and simultaneously recorded with high resolution by using multiple diffraction planes of the same quartz crystal operating in Cauchois transmission geometry. The W Kα transitions were dispersed by the (5 0 2) planes, which were perpendicular to the crystal entrance surface, and by the (6 0 2), (7 0 2), and (8 0 4) planes which were rotated with respect to the (5 0 2) planes by angles up to 4.80°. The W Lγ transitions were dispersed by the (2 0 1) planes rotated from the (5 0 2) planes by 4.01°. The spectra from the five planes were simultaneously recorded on image plate detectors, and spectra were also recorded by scanning solid-state electronic detectors with narrow slits across the spectral lines. The metrology of the L and K shell spectra diffracted from multiple quartz planes enabled the detailed analysis of the detector spatial resolution and accurate measurement of the instrumental broadening produced by the various quartz diffraction planes. The W Lγ spectra had the highest instrumental resolving power, 1800, permitting for the first time the resolution of the blended Lγ4′ (L1O2) and Lγ4 (L1O3) transitions. After subtracting the instrumental and detector contributions to the line widths, the remainder was assigned to the natural line widths. The measured widths of the O2 and O3 levels were 2.9 eV and 1.9 eV, respectively, and based on atomic code calculations these widths are attributed to the O2O3O4 and O3O4O5 super Coster–Kronig processes. This work demonstrates the ability to simultaneously record high resolution (<1 eV) L and K spectra to determine the line shapes of the heavy elements (e.g. W through Am) by using multiple planes of a single quartz crystal and to accurately measure the non-radiative super Coster–Kronig rates which are closely related to the energy level structure of the outer shells of the heavy elements.

A many-body theory of the Ti M 2,3-VV Auger-photoelectron coincidence spectroscopy (APECS) spectrum of TiO 2(1 1 0)

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 2 L 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 3 L 3〉 in Ti M 2,3 main line (or satellite) of TiO 2(1 1 0) live longer than the Ti ∣ cd 3 L 3〉 → ∣d 1 L 3〉 sCK decay so that the Coulomb repulsion from the surrounding Ti ions gives the O + ion desorption from the surface.

Missing Auger electron emission lines of metallic Sn and Auger-photoelectron coincidence spectroscopy (APECS)

Abstract The M 4,5–N 2,3N 2,3 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 M 4,5–N 2,3N 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 N 2,3N 2,3–N 4,5N 4,5N 4,5N 4,5 and N 2,3N 2,3–N 2,3N 4,5N 4,5 super Coster–Kronig (sCK) transitions. The present theory shows that one should be able to detect the missing M 4,5–N 2,3N 2,3 AES lines by measuring the M 4,5 photoelectron spectroscopy (PES) spectrum in coincidence with the M 4,5–N 2,3N 2,3 Auger decay. The lifetime width of the two N 2,3 holes is much larger than the effective Coulomb hole–hole interaction energy U between the two N 2,3 holes so that the multiplet coupling between the two N 2,3 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).

Localization and screening in GdNi alloy films

Gd/Ni compounds with different Gd concentration have been investigated with constant initial state spectroscopy (CIS) of photoemission utilizing the light of synchrotron radiation. The photoemission cross-sections of Gd 5d and 4f states show a strong resonance in CIS spectra at the Gd 5p absorption edge. The screenings of Gd ions by Ni 3d conduction electrons results in a dramatic suppression of the 5p64f75d16s2 to 5p54f75d26s2 resonant enhancement of photoemission valence band intensities. This decrease in the super-Coster–Kronig photoemission resonant enhancement of the valence band can be related to the hybridized Gd 5d and Ni 3d bands near the Fermi level, consistent with performed first-principles calculations of local densities of states.

Why are the band-like states suppressed in the M 3–M 4,5M 4,5 super Coster–Kronig electron spectrum of Cu metal compared to those in the L 3–M 4,5M 4,5 Auger electron spectrum?

The relative spectral intensity of the band-like two M 4,5-hole state to the atomic-like localized one is much suppressed in the coincidence M 3–M 4,5M 4,5 super Coster–Kronig (sCK) electron spectrum of Cu metal compared to the one in the coincidence L 3–M 4,5M 4,5 Auger electron spectroscopy (AES) spectrum. The M 3-hole lifetime width of Cu metal is calculated by an ab initio atomic many-body theory (the extended relaxed core random phase approximation with exchange). The calculated M 3-hole lifetime width of Cu metal agrees well with the experimental one. The M 3–M 4,5M 4,5 sCK decay width of Cu metal decreases much with delocalization of the two M 4,5 holes in the sCK final state, whereas the Auger decay width is fairly independent of localization and delocalization of the two M 4,5 holes in the Auger final state. Thus, the relative spectral intensity of the band-like state is much suppressed in the coincidence M 3–M 4,5M 4,5 sCK-electron spectrum of Cu metal compared to the one in the coincidence L 3–M 4,5M 4,5 AES spectrum.

M ξ, M αβ, M γ and M m X-ray production cross-sections for elements with 71⩽ z⩽92 at 5.96 keV photon energy

The M ξ, M αβ, M γ and M m X-ray production (XRP) cross-sections have been measured for the elements with 71⩽ Z⩽92 at 5.96 keV incident photon energy satisfying E M1< E inc< E L3, where E M1(L3) is the M 1(L 3) subshell binding energy. These XRP cross-sections have been calculated using photoionization cross-sections based on the relativistic Dirac–Hartree–Slater (RDHS) model with three sets of X-ray emission rates, fluorescence, Coster–Kronig and super Coster–Kronig yields based on (i) the non-relativistic Hartree–Slater (NRHS) potential model, (ii) the RDHS model and (iii) the relativistic Dirac–Fock (RDF) model. For the third set, the M i ( i=1–5) subshell fluorescence yields have been calculated using the RDF model-based X-ray emission rates and total widths reevaluated to incorporate the RDF model-based radiative widths. The measured cross-sections have been compared with the calculated values to check the applicability of the physical parameters based on different models.

Many-body effect in the N 23-VV Auger-photoelectron coincidence spectroscopy (APECS) spectra of Ag metal

The coincidence N23-VV Auger-electron spectroscopy (AES) spectra and N23 photoelectron spectroscopy (PES) spectra of Ag metal are analyzed. Here N X is the notation for atomic shell N x ( X = 2, 3). The band-like feature in the coincidence N23-VV AES spectra is much more intense than that in the coincidence M45-VV ones because the potential in the delocalized two-hole state is less attractive than that in the localized one. The partial N23-VV super Coster–Kronig (sCK) transition rate depends critically on both the final-state potential and the sCK-electron kinetic energy (KE) because the KE is low, whereas the partial M45-VV Auger-transition rate is fairly independent of them because the KE is very high. As a result, the partial sCK-transition rate to the band-like state is enhanced compared to that to the atomic-like localized state. The low KE tail in the coincidence N23-VV AES spectra which is likely due to the sCK transition involving more than two electrons, is more enhanced than that in the coincidence M45-VV ones. This is due to the enhancement of the partial sCK-transition rate by the presence of extra holes in the final state. The sharp peaks of small intensity on the lower KE side of the main line in the coincidence N2 PES spectrum are tentatively attributed to the shakeup satellites.

MVV super Coster–Kronig spectra of nickel near the excitation threshold

The MVV super Coster–Kronig (sCK) spectra of metallic Ni have been measurednear the 3p excitation threshold by varying excitation photon energy. The resultshave been interpreted on the basis of the Cini–Sawatzky theory. The measuredsCK band has composite structure with features at electron kinetic energy of49.8, 56.3, 59.5, and 60.5 eV. If we interpret the band at 49.8 eV to be the split-offquasi-atomic band, we can estimate the effective intra-atomic Coulomb energy ata large value of 8 eV. The spectral shape of the MVV sCK band measured byexcitation with vacuum ultraviolet light does not coincide with that obtained by theMg K α excitation orwith that of the L3VV Coster–Kronig band. The shape of the MVV sCK spectrum changes as excitation energychanges. The excitation-energy range in which such spectral change occurs extends fromthe 3p threshold to 10 eV above it. As the kinetic energy for the MVV sCK band starts tooverlap that of the two-hole-bound-state band, the MVV sCK band changes its shapeconsiderably and the two spectra become inseparable. In this excitation-energy region, thespectator electron excited optically forms a virtual bound state with the two 3d holes. Thelocation of the apparent two-hole-bound-state band shifts toward high binding energy onthe 3p–3d resonance. This can be interpreted as a kind of final state interaction. Thesuggested intermediate and final states of the single-step transition are consistent withthe constant-initial-state spectra and total photoyield spectrum. The roles ofthe screening by conduction electrons and the sd hybridization are emphasized.

Calculation of the yield of Xe i+ photoions upon the decay of M 45 vacancies through intermediate states in coincidence with energy-selected Auger electrons

A theoretical model is proposed for calculating the yield of photoions detected in coincidence with energy-selected Auger electrons. This model provides a correct explanation for experimental data on the yield of photoions upon ionization of the M 45 shell of xenon atoms. In the framework of the proposed model, the intermediate-coupling approximation is used to calculate both the structure of the terms of the N −2 two-hole states generated through the M 45 NN Auger decays and the probabilities of branching due to decays of these states into three-hole states upon the Auger, Coster—Kronig, and super-Coster—Kronig transitions. The probabilities of branching for subsequent branches of the cascade decay are calculated in the configuration-average approximation. The results of these calculations are in good agreement with the experimental data.

Electron-impact ionization of Ti3+ ions

Absolute cross sections for electron-impact single ionization of potassium-like titanium have been measured from threshold to 1000 eV using a crossed-beams experimental set-up. A 0.5 eV resolution energy-scan technique revealed structures in the cross section in the range from 40 eV to 150 eV due to dominant contributions of indirect ionization mechanisms. A large fraction of the cross section is due to excitation–autoionization proceeding via intermediate excited states 3p5(3d2 3F) 2F, 3p5(3d2 3P) 2P, 3p5(3d2 3F) 2D which subsequently decay by super-Coster–Kronig transitions. The results of the measurements are in satisfactory agreement with previous advanced theoretical calculations.

Calculation of Xei+ photoion yields in coincidence with energy-selected M45NN Auger electrons

A theoretical model to calculate the photoion yields registered in coincidence with fixed-energy Auger electrons is developed. The intermediate-coupling approximation is used to calculate the term structure of the two-hole states reached by Auger transitions, and the branching ratios of their further Auger, Coster–Kronig and super Coster–Kronig decays into the three-hole states. The remaining parts of the cascading decay de-excitation trees are simulated in configuration-average approximation for branching ratios and transition energies. Our calculation allowed us to explain the recent M45NN Auger-electron–photoion coincidence experiment upon M45 photoionization of Xe.

Branching ratios of multiply charged ions formed through photoionization of Kr 3d, 3p and3s sub-shells using a coincidence technique

Multiple-charged Kr ions have been studied using monochromatized synchrotronradiation combined with a coincidence technique. The multiple-charged ions formedthrough ionization of the inner sub-shells were detected by a time-of-flight massanalyser and the photoelectrons emitted from those orbitals were observed by acylindrical mirror electron energy analyser. The coincidence measurement betweenthe energy-selected photoelectron and the photoion specified the individualmultiple ionization channels of Kr. The Kr 3d ionization produces doubly andtriply charged ions. The Kr 3p ionization mainly yields triply charged Kr ions viaM23M45N23 Coster–Kronigdecays, and the M23M45N1 decays generate considerably quadruply charged ions. The 3s ionization significantlyproduces quadruply charged ions via super-Coster–Kronig decays with successive Augertransitions.

Correlation between the relaxation energy shift and the hole-lifetime width

By analyzing the residual energy shift between the experimental atomic core-hole energy and the relativistic atomic ΔSCF hole energy of atomic Zn, Kr, Cd, Xe and Hg, we examined whether within any principal shell there is any simple correlation between the relaxation energy shift and the lifetime width of the core hole. We studied the core hole in the same principal atomic shell so that the relaxation energy shift and the lifetime width are governed by the super Coster–Kronig transition, in which the occupied orbitals of the same principal quantum number are involved. Within any principal shell there is no simple correlation between the relaxation energy shift and the lifetime width. The large correlation coefficient found in the case of the N shell of Hg atom by McGilp and Weightman [J. Phys. B13 (1980) 1953] is fortuitous.

Effect of the final-state interaction on the initial core–hole lifetime: the case of the 4s-hole lifetime of Sn metal

The first theoretical study of the effect of the final-state interaction on the initial core–hole lifetime is presented. The 4s-hole lifetime width of Sn metal is calculated by an ab-initio atomic many-body theory (Green’s function method). When the final-state interaction in the 4p4d two-hole state, created by the 4s −1−4p −14d −1 εf super Coster–Kronig (CK) transition of the initial 4s hole, is explicitly taken into account, the ab-initio atomic many-body calculation of the 4s-hole X-ray photoelectron spectroscopy (XPS) spectrum of Sn atom can provide excellent agreement with experiment in both the 4s-hole energy and the 4s-hole lifetime width. Otherwise, the many-body calculation underestimates considerably the 4s-hole lifetime width. The 4p4d two-hole state interacts strongly with the 4d triple-hole state by the 4p −14d −1−4d −3 εf super CK transition. The interaction affects greatly the initial 4s-hole lifetime width.

Electronic structure of β-FeSi 2 obtained by maximum entropy method and photoemission spectroscopy

The electronic structure of β-FeSi 2 was investigated by maximum entropy method (MEM) and photoemission spectroscopy. The electronic structure obtained by MEM using X-ray diffraction data at room temperature (RT) showed covalent bonds of Fe–Si and Si–Si electrons. The photoemission spectra of β-FeSi 2 at RT were changed by incidence photon energies. For photon energies between 50 and 100 eV, resonant photoemission spectra caused by a super Coster–Kronig transition were observed. In order to reduce resonant effect about Fe(3d) for obtained photoemission spectra, difference spectrum between 53 and 57 eV was calculated, and it was compared with ab-initio band calculation and spectra function.