L-Edge Absorption Spectra of the Rare Earths: Assessment of the Single-Particle Picture

X-ray $L$ absorption spectra were measured for the rare-earth metals Sm and from Gd to Lu. The data are compared with single-particle band-structure calculations over an energy range of about 100 eV. The one-electron theory describes the white line and the near-edge structure strikingly well. At higher energies, although all features of the experimental spectra are reproduced by the calculation, the actual placement of the features shows discrepancies, which point to a limitation in the one-electron description.