Abstract
Excitations of the subshell in the transition metals and their oxides have been studied by inelastic scattering of 75-keV electrons. The "white lines" which arise from dipole transitions to unoccupied states have been investigated in terms of their threshold energies, widths, and intensity ratios. Shifts in the threshold energy between the metal and oxide are different from the chemical shifts measured by x-ray photoemission spectroscopy and this suggests the importance of relaxation effects. Single-particle calculations for the spectra are also discussed. Measured linewidths are generally larger than those predicted by suitably broadened theory. A variation from the statistical -to- white-line intensity ratio of 2:1 has been observed across the transition row, with values ranging between 0.8:1 for Ti to 5:1 for FeO. This behavior appears to be associated with the white lines since Cu with a filled band exhibits the statistical results. It is suggested that the anomalous ratios may be explained by a breakdown of coupling caused by an exchange mechanism. Finally, the extended x-ray absorption fine-structure-type structure extending several hundred eV above the white lines is analyzed for Cr to provide the radial distribution function.
- Received 25 November 1981
DOI:https://doi.org/10.1103/PhysRevB.26.614
©1982 American Physical Society