Super Coster-Kronig Transitions Research Articles

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.

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.

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.

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.

Resonant structure due to the 3 p→3 d transition in the photoionization of Ca +

Many-body perturbation theory has been used to calculate the resonance structure (3 p→3 d) into the photoionization (4 s→ kp) for ion Ca +. This resonance structure results from the interference between a photoionization process or a photoionization with excitation process and a resonant Auger process. The coupled equation method has been improved to calculate this interference by the summation of specific classes of diagrams of perturbation theory to infinite order. The resonance structure in the region of the 3p threshold is enhanced via a super-Coster–Kronig transition. The theoretical results are in good agreement with experiment.

Multielectron excitations probed by helicity-modulation XMCD at K-edge in 3d transition metal compounds.

Multielectron excitations (MEE) have been investigated using X-ray magnetic circular dichroism (XMCD) at the K-edge in 3d transition metal compounds. In the range of 50-70 eV above the absorption edge, a dichroic signal that is associated with MEE was identified. This phenomenon is thought to occur due to the super Coster-Kronig transition described as the final states (1s)1(3p)5(3d)n+2 resulting from the 3p --> 3d transitions. In order to verify this interpretation, XMCD measurements using the helicity-modulation method and calculations of the dichroic spectrum were performed based on this super Coster-Kronig transition.

WIDTHS OF THE ATOMIC K–N7 LEVELS

Atomic level widths obtained from experimental measurements are collected in Table I, along with the corresponding theoretical widths derived from the Evaluated Atomic Data Library (EADL) of Lawrence Livermore National Laboratory; these EADL values are based upon the Dirac–Hartree–Slater version of the independent-particle model. In a minority of cases, many-body theory predictions are also provided. A brief discussion of the manner in which the experimental widths were deduced from spectroscopic data is included. The bulk of the data are for elements in the solid state, but a few data for gases and simple compounds are included.For the K, L2, L3, and M5 levels, where Coster–Kronig contributions do not contribute or contribute only to a small extent to the overall widths, the EADL predictions appear satisfactory for elements in the solid state. For other levels, where Coster–Kronig and super-Coster–Kronig transitions have large probabilities within the independent-particle model, this model is not satisfactory. Table II provides a complete set of recommended elemental values based upon consideration of the available experimental data.

Multielectron Excitations in3dTransition Metal Compounds Probed by X-Ray Magnetic Circular Dichroism

Multielectron excitations (MEE) have been investigated using X-ray magnetic circular dichroism at the K -edge in 3 d transition metal ferromagnetic and ferrimagnetic compounds. The MEE dichroic signal is located in the energy range 50 to 70 eV above the absorption edge. The intensity is of the order of 10 -3 of the photoabsorption, comparable to the dichroism observed around the edge. The energy position is dependent on the absorbing magnetic atoms rather than the material structures. The energy difference between the K -edge and the MEE peak varies linearly with the atomic number Z , and is related to the absorption energy of the M 2,3 -edge of the ( Z +1) atom. These features suggest that the 3 d -states have a significant contribution to the MEE process. We propose that this MEE phenomenon is due to the super Coster-Kronig transitions described as the final state (1 s ) 1 (3 p ) 5 (3 d ) n +2 , in which two electrons are simultaneously excited to the 3 d -orbitals.

XES studies of La-Sr-Cu-O and Y-Ba-Cu-O ceramics

X-ray emission spectroscopic studies of superconducting ceramics characterised by the following compositions: La2.19Sr0.07Cu1.05Ox, Y0.9Ba1.8Cu3.3Oy and Y0.9Ba2.0Cu3.1Oy, as well as of a semiconducting ceramic, Y1.9Ba1.0Cu1.1Oz, have been performed using spectrometers of an electron probe microanalyser. Concentrations of the superconducting phases and semiconducting one exceeded 80% of the whole sample compositions. The CuLα spectra detected for superconducting samples revealed a satellite maximum connected with Cu3+ ions lying at+1.4 eV in the high energy side of the spectrum. Mean valence of copper ions in the La−Sr−Cu−O sample has been estimated to be +2.16 and for the Y0.9Ba2.0Cu3.1Oy, sample above+2.1. It was confirmed that the binding energy of 3d electrons taking part in the electronic transition involving this satellite maximum and the main one is equal to 3.5 eV. The satellite at+2.6 eV is connected with states close to the Fermi level, and the satellite caused by theM2,3M4,5M4,5 super Coster-Kronig transition at about 4.2 eV has been established. Analysis of the LaLγ4 spectrum showed evidence for weak bonding between the lanthanum ions and oxygen ions.

A Theory of Resonant Photoemission in Copper Halides

A theory is presented for the resonant photoemission of insulators. Interference effect between the direct valence electron excitation and the core-electron excitation followed by the super Coster-Kronig transition is examined. Our previous theory is extended to include the hybridization of the valence state to the conduction band. It is shown that the satellite intensity persists far below the core-level photothreshold and exhibits a Fano type antiresonance, in agreement with the recent experiment of copper halides by Ishii et al .

M2,3-shell Auger and autoionisation spectra of free Cr, Mn, Fe, Co, Ni and Cu atoms

The M2,3M4,5M4,5 Auger and autoionisation spectra of atomic Cr, Mn, Fe, Co, Ni and Cu have been measured using 1.5 keV electron beam excitation. The spectra are dominated by Coster-Kronig and super Coster-Kronig transitions following 3p63dn4sm to 3p53dn+14sm excitation and 3p63dn4sm to 3p53dn+4sm epsilon l ionisation. The strong coupling of the 3p63dn4sm to 3p63dn-14sm epsilon l ionisation and the 3p63dn4sm to 3p53dn+14sm excitation gives rise to asymmetric Fano-type profiles of the 3p53dn+14sm to 3p63dn-14sm epsilon l lines.

Final State Interactions of Inner Core Absorption Excitation in Transition Metal Halides

Absorption spectra resulting from the inner 3p-shell excitation of transition metal ions in halide compounds are measured in the photon energy range from 25 to 140 eV with synchrotron radiation from SOR-RING. The observed characteristic multiplet structures spreading over 10–20 eV are well explained by the localized excitation model for the 3p 5 3d m+1 excited states, providing the evaluation of the final state interactions. The asymmetry of the absorption bands of the transition metal compounds with more than half-filled 3d-shell is interpreted as due to the interference caused by the super Coster-Kronig transition, in contrast to the rather symmetric and broad spectral line shape in the compounds with less than half-filled 3d-shell.

The N4,5N6,7N6,7 and N4,5N6,7O4,5 Auger spectra of Au, Pt and Ir

The relative intensities of N 4,5 N 6,7, N 4,5 N 6,7 O 4,5 and N 4,5 N 6,7 O 2,3 transitions in clean Au, Pt and Ir are measured, and the relative roles of super-Coster—Kronig and Coster—Kronig de-excitation of N 4,5 holes are discussed. Super-Coster—Kronig transitions account for more than half the de-excitation in Au, and become increasingly dominant as the number of O 4,5 electrons in the metal decreases. High-resolution measurements of the N 4,5 N 6,7 X transitions ( X= N 6,7, O 1, O 2,3, O 4,5 in Au, Pt and Ir have been presented. Although there are detailed discrepancies in relation to the theory of McGuire, the super-Coster—Kronig transitions are always more intense than the Coster—Kronig transitions, and the intensity of the N 4,5 N 6,7 O 4,5 transitions falls rapidly as the number of O 4,5 electrons decreases.

Resonant photoemission from SmS(100)

A strong, sharp resonance enhancement of 4f photoemission has been observed on SmS(100) surfaces for photon energies in the region of the 4d-4f transitions at about 126 eV. The discrete final state reached via the excitation hν+4d 104f 6→4d 94f 7 autoionizes primarely via a super Coster-Kronig transition of the type 4d 94f 7→4d 104f 5 + unbound electron. Other decay channels, e.g, Sm 5p emission, as well as a surface induced binding energy shift in the Sm 3+ final state are identified and discussed.

Many-electron effects in the 3p X-ray photoelectron spectrum of Kr

The X-ray photoelectron spectrum of Kr in the neighbourhood of the main 3p lines has been calculated using diagrammatic many-body theory for the 3p self-energy and spectral function. Super Coster-Kronig 3p to or from 3d2epsilon f dipole fluctuations are found to shift the 3p lines by about 3 eV from their Delta SCF positions, the dipole shift being approximately 30% of the Delta SCF monopole relaxation shift. For determining the 3p linewidth the 3p to 3d4s epsilon p and 3p to 3d4p epsilon d Coster-Kronig transitions and the super Coster-Kronig transitions are approximately equally important. The calculated positions and widths of the 3p main lines are in good agreement with experiment.

AUGER TRANSITIONS IN SINGLY AND MULTIPLY IONIZED ATOMS

— Some recent progress in Auger and autoionizing electron spectrometry of free metal atoms and of multiply ionized atoms is reviewed. The differences which arise between the spectra of atoms in the gaseous and the solid state are due to solid state effects. This will be shown for Cd as an example. The super Coster-Kronig transitions 3p-3d (hole notation) and Coster-Kronig transitions 3p-3d4s have been measured and compared with free-atom calculations for free Zn atoms. The experimental width r(3p) = (2.1 ± 0.2) eV found for the free atom agrees with the value obtained for solid Zn but is considerably smaller than the theoretical value for the free atom. Autoionizing spectra of Na following an L-shell excitation or ionization by different particles are compared and discussed. The nonisotropic angular distribution of electrons from the transition 2p 3s P3/2 -*• 2p + e is compared with theoretical calculations. Two examples for Auger spectrometry of multiply ionized atoms are given : (1) excitation of neon target atoms by light and heavy ions, and (2) excitation of projectile ions Be and B in single gas collisions with CH4. A Strong alignment of the excited atoms has also been found here.

Lifetime Broadening and CI-Resonances Observed in ESCA

The electron spectrum of the M2 and M3 levels in bromine and krypton have been studied by high resolution ESCA. The M1M2,3M2,3 super Coster-Kronig transitions become energetically forbidden for Zless than sim-36 (Kr) and recent calculations therefore predict a decrease in the M2 and M3 natural linewidths around krypton in the periodic system. The experiment shows that the 3p3/2 linewidth is smaller in Kr than in Br. It is, however, also found that this decrease in linewidth is followed by configuration interaction (CI) between 3p2P and 3d2nl*2P states. Several descrete CI resonances are observed in the Kr 3p spectrum. Such resonances are also studied in the N shell for the elements from Te (Z = 52) to Ba (Z = 56). For these elements the effect is found to be much larger due to the strong collective character of 4d-nf* excitations.

Interpretation of 3 p-core-excitation spectra in Cr, Mn, Fe, Co, and Ni

Recent measurements of the 3 p-core-excitation spectra of Cr, Mn, Fe, Co, and Ni are interpreted with an atomic model. The dispersion like line shape observed in these metals is attributed to the interference of 3 p 63 d N → 3 p 53 d N+1 , which decays to 3 p 63 d N−1 ϵf via a super Coster-Kronig transition, with the direct excitation of 3 p 63 d N → 3 p 63 d N−1 ϵf. The overall width of the line and some weaker features associated with it are related to the multiplet splittings of 3 p 53 d N+1 . The more symmetric line shape found for Cr, which is thought to be due to the absence of a large local moment, is explained in terms of the greater number of multiplets that contribute for a small moment ( S= 1 2 ) as compared to a large moment ( S= 5 2 ).

Core and valence orbitals in solid and gaseous mercury by means of ESCA

Abstract The electronic structure of Hg has been studied by means of high resolution ESCA, using monochromatized AlKα excitation. The atomic spectrum from the gas phase is compared with the solid state spectrum from frozen Hg. Electron binding energies and natural linewidths of the levels in the N, O and P shells are reported and compared with data from recent calculations. The calculations were found systematically to overestimate the linewidths when Coster-Kronig and super Coster-Kronig transitions are involved. The concept “phase transition shift” is defined and the observed phase transition shift upon sublimation of Hg is discussed. A possible relation between the cohesive energy and the difference in core and valence level phase transition shift is pointed out. The 4 f inelastic and shake-up spectrum from atomic Hg is analyzed and compared with the corresponding spectrum from solid Hg. The formation—upon sublimation—of the broad, free electron-like sp -valence band from the atomic 6 s level is demonstrated in the electron spectra. A theoretical density of states spectrum is obtained from a relativistic band structure calculation, assuming spherical symmetry. The prominent features in the theoretical spectrum were found to agree well with those of the electron spectrum.