The 4d edges of Ta, Pt, and Au were measured by means of reflection-electron energy-loss spectroscopy for different primary-beam energies ${\mathit{E}}_{\mathit{p}}$ in the maximum range 884<${\mathit{E}}_{\mathit{p}}$<2186 eV with the aim of investigating the nature of the electronic transitions involved at this edge. In order to allow a proper comparison of the measured edge intensities to each other, a normalization procedure was developed. On the basis of soft-x-ray-absorption spectroscopy data and by means of a theoretical muffin-tin generalized oscillator strength and differential cross-section calculations, it was possible to determine that nondipole d-d electron transitions are dominant at the 4d edges of all three elements. The observed edge-intensity decrease as a function of increasing atomic number is explained also on the basis of the amount of empty d-character states available at the Fermi level in each element.

• Received 5 March 1992

DOI:https://doi.org/10.1103/PhysRevB.46.15660