A D Laine

Atomic structure calculations for the analysis of Auger parameters of elements K to Kr

The values of atomic parameters, k and dk/dN, used in the analysis of Auger parameter shifts have been determined from the results of atomic structure calculations for the elements K to Kr. The values of the parameters for free atoms have been corrected for the effect of valence electron compression in solids. Calculations for Ni and Ge shows that the values obtained for the atomic parameters are independent of the configuration of passive valence electrons and of the character of the inner shell core hole.

Off-Site Contributions to Electron Correlation; An Extension to the Hubbard Model Studied by Auger Spectroscopy

A new theory of the lineshape of CVV Auger processes has been developed which extends the Hubbard Hamiltonian to include off-site correlation effects. The new theory shows that the neglect of off-site correlations explains the failure of the standard Cini-Sawatzky model of CVV processes to yield simultaneous agreement with the experimental kinetic energy and profile of the N6,7O4,5O4,5 Auger spectra of Au which correspond to the U > W, quasi-atomic, case. The theory predicts that the contribution from off-site correlations will be less important in the U < W, bandlike region, and this is shown to be consistent with the results of high-resolution measurements of the KVV spectrum of Si.

Simplification of the N6.7O4.5O4.5 Auger spectrum of Au

The N7O4.5O4.5 and N6.7O4.5O4.5 Auger spectra of metallic Au have been measured separately by using synchrotron radiation to scan through the N7 and N6 electron levels. Subtracting the N7O4.5O4.5 spectrum from the combined N6.7O4.5O4.5 Auger profile yields the N6O4.5O4.5 contribution.

The unoccupied states of tungsten(001) and tungsten(110): theory and experiment

The results of relativistic photocurrent calculations, based on the one-step model of photoemission, used here to simulate inverse photoemission spectroscopy (IPES) experiments from the W(001) and W(110) surfaces are presented. The isochromat IPES spectra, for photon energies ranging between 15 and 30 eV, were recorded for electrons incident normal to the (001) and (110) crystal surfaces, corresponding to transitions in the Gamma H and Gamma N directions of the three-dimensional Brillouin zone respectively. This combined theoretical and experimental study is used to investigate the electronic structure, in particular the bulk electronic structure, of these systems. The calculated spectra are found to be in good overall agreement with the corresponding experimental results. The origins of the remaining discrepancies between theory and experiment are discussed.

The orbital character of the core-hole screening charge in metallic Mg

Atomic-like transition rate calculations have been performed for the KL1V and KL2.3V Auger processes in metallic magnesium. The valence screening configuration is varied in order to reproduce the experimental KL1Vs:KL1Vp, KL2.3Vs:KL2.3Vp, and KL1V:KL2.3V intensity ratios. The theoretical results are in best agreement with experiment for a screening configuration surrounding the 1s core-hole of 3s13p2. This result is in conflict with previous analyses of core-hole screening in magnesium.

Auger transition rates for systems with open subshells

McGuire (1975) has given a general expression for the evaluation of Auger transition rates in multiply ionised atoms. Simplified expressions are derived, in various coupling schemes appropriate to the particular cases in which the multiple ionisation is restricted to those subshells directly involved in the Auger transitions. The cases in which the final state holes are inequivalent or equivalent are treated separately. The analysis is used to calculate the Auger transition rates of the Mg KL2,3-L2,32 V Auger vacancy satellites.

Unoccupied surface states of W(001) studied by angle-resolved ultraviolet inverse photoemission

Isochromat inverse photoemission spectroscopy (IPES), at a photon energy of 20 eV, has been used to map an intrinsic surface state/resonance in the Gamma M direction of the W(001) two-dimensional Brillouin zone. The state is found just above the Fermi level approaching halfway along the Sigma line and disperses upwards to approximately 2 eV above the Fermi level towards M. Calculations of the surface electronic structure and the role of the surface states in the reconstruction of the W(001) surface are discussed in the light of the data presented together with existing high-resolution angle-resolved photoemission spectroscopy data.

The virtual bound states of Fe in AuFe studied by photoemission

By using synchrotron radiation photoemission with photon energies near to the Cooper minimum of Au the authors have detected virtual bound states (VBS) in Au90Fe10. A VBS peaking 0.7 eV below the Fermi energy is attributed to Fe minority states. Less intense features are observed at about 2.3 eV, 4-5.5 eV and 7.3 eV below the Fermi energy, close to the edges of the Au 5d bands, which they suggest are due to the Fe majority states broadened by strong hybridization with the Au valence band. These observations agree with the Friedel-Anderson model which predicts nondegenerate virtual levels with the majority spin population completely occupied and with the minority states spanning the Fermi level.

An Investigation Of The Kl2,3-]L2,3l2,3 V Auger Satellites Of Mg And Al

The KL2.3 to L2.3L2.3 V Auger vacancy satellite transitions of Mg and Al, which lie to high kinetic energy of the KL2.3 V Auger profile, are analysed using a combination of self-consistent densities of states (DOS) and atomic-like Auger transition rate calculations. The transition rate calculations demonstrate that previous work based on statistical weight arguments is incorrect. The DOS calculations show that the valence s contribution to the local DOS forms a bound state in the presence of a double core-hole state, though the major contribution to the core-hole screening is provided by the local p DOS. The calculation successfully reproduces the spectral profile for the Al transitions, but is unable to account for one of the features in the Mg spectrum.

Core-hole screening in metallic magnesium

An atomic-like formalism has been used to calculate the KL1V Auger transition rate for magnesium as a function of the initial-state valence configuration. The transition rate for KL1V processes involving valence s and p holes, KL1Vs and KL1Vp, have been calculated for several valence configurations. A comparison between the theoretical and the experimental values of the KL1Vs:KL1Vp ratio suggests that a 1s core hole in metallic magnesium is screened by a valence charge of p character.