Core-hole screening in lanthanide metals

The multicomponent structure of the $3d$ x-ray photoemission spectra of the light rare-earth metals is elucidated in terms of recent x-ray absorption and appearance-potential spectroscopy results for these materials. Both multiplet splitting due to $3d-4f$ exchange and satellite structure due to two competing screening mechanisms are identified. The main component of the $3d$ line arises when the core hole is screened by $5d$ conduction electrons; the satellite from a $4f^n\to 4f^{n+1\mathrm{}}$ process. The satellites in the metals occur at lower binding energies because the empty $4f$ level falls below the Fermi energy. This interpretation is supported by an "equivalent cores" argument.