T. S. Ivanchenko

X-ray absorption fine-structure investigation of the ionic compounds NaBr, KBr and RbCl: full multiple-scattering analysis

The x-ray absorption near-edge structures (XANESs) of the Br K edge in NaBr and KBr and the Rb K edge in RbCl have been analysed. In spite of the fact that these compounds have the same type of crystal lattice (NaCl type) the published experimental spectra show different structures. We have used a full multiple-scattering method to investigate the conduction band structures of NaBr, KBr and RbCl. The partial densities of Br and Rb p states in the conduction bands were obtained over a large energy interval for both the ground and the excited states. The latter were used to analyse the experimental data. In contrast with our recent study of AgBr, the Br K XANESs in NaBr and KBr and the Rb K XANES in RbCl are found to be determined by the multiple scattering of photoelectrons in a large cluster (30 or more atoms). We also show that, for the energy interval up to 80 eV above the main edge, the single-scattering approximation in the present study seems to be less satisfactory.

L3 edge X-ray absorption spectrum of CeO2: crystal structure effects

Abstract We report the interpretation of all spectral features of Ce L 3 XANES over the 40 eV range. The wave function of the excited electron in the final states of the Ce L 3 edge XANES spectrum is found to be determined by the multiple-scattering processes in a large size cluster formed by at least 45 atoms. The many-body final states for the 2p → 5, ed transition, arising from the configuration interaction due to mixing of Ce 4f and O 2p valence orbitals, have been recalculated taking into account the crystal field splitting of the 5,ed states. The results give full explanation of the low energy shoulder on the Ce L 3 XAS white line that was object of a long-standing discussion.

Unoccupied states in the rare earth monosulfides: A sulfur XANES study

Abstract The experimental sulfur XANES spectra in SmxGd1−xS system have been measured and analyzed in the framework of one-electron multiple scattering theory. It was found that sulfur K-edge XANES in these compounds is dominated by one-electron transitions, therefore this spectrum probes the unoccupied states projected on the S site in the conduction band of this rare-earth monosulfide. In the energy interval from about 10 eV to 17 eV above the main edge we have found evidence for shake-up excitations.