Comparative study of the electronic structure of the ordered and disordered Cu3Au (100) and Cu3Au (110) surfaces

The influence of structural changes on the electronic structure has been investigated by a comparison of the angle-integrated valence and core level photoelectron spectra of ordered and disordered Cu₃Au(100) and (110) surfaces. The total width of the Au 5d and Cu 3d bands does not change with the ordering state or surface orientation. The spectra for the (100) surface are compared with selfconsistent calculations and good agreement is found, for the ordered state, however with a 0.6 eV correction of the calculated Fermi level position. We observe three Au 5d derived bands at 5.1, 6.0 and 6.9 eV, in contrast to previous experimental findings. Our results indicate the existence of shortrange order above the critical temperature.     

The electronic structure of ordered Cu3Au(001)

The electronic structure of the (001) face of ordered Cu₃Au was studied using synchrotron radiation at BESSY, in the photon energy range 22–80 eV. The Cu 3d-derived bands in Cu₃Au look like the foldedd-bands of fcc Cu metal. Three Au 5d-derived bands were observed at 5.0, 6.1 and 7.0 eV below the Fermi level, which showed no dispersion with change in photon energy. The Cu 3d- and the Au 5d-derived bands are found to be separated in energy. We have calculated self-consistent energy bands along the (001) direction using the fully relativistic LMTO method. Comparison of these bands with those experimentally determined shows good agreement. From the calculated bands along –X the direction dependent densities of states were determined, which give a consistent account for the non-dispersive Au-bands.     

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Recent progress in the study of photoionization processes of atomic species by electron spectroscopy using synchrotron radiation

The use of the synchrotron radiation emitted by the ACO storage ring has recently produced new significant results in the study of single and multiple photoionization processes in atoms. With photon flux in the 10¹⁰-10¹¹ photons/sec in 1 % band width between 30 and 110 eV, we have been able to investigate photoionization processes with cross sections as low as 0.01 megabarn. It has thus been possible to study the correlation satellites in helium, argon and xenon, to determine subshell photoionization cross sections, including the variation of branching ratios due to the spin-orbit splitting, to produce photoemission spectra of metallic vapors and to observe threshold effects, like the post collision interaction.     

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