Resonant5fvalence-band satellite at the5dthreshold in uranium metal

Photoelectron energy distribution curves for polycrystalline $\alpha$-uranium show a giant Fano-type resonance for the intensity of the $5f$ valence-band features at the Fermi energy $E_F$, when the photon energy is tuned through the $5d$ core absorption edge at around $h\nu \approx 94 \mathrm{to} 103$ eV. Further, a sharp (full width at half maximum = 2.2 eV) $5f$ satellite excitation at an initial energy $E_i=-2.3\mathrm{}$ eV below $E_F$ has been observed, which has a close analogy to the "6 eV satellite" in Ni. This shakeup satellite shows also a strong resonant enhancement (≥ 6 times) at the $5d$ core-level threshold, but a distinctly different cross-section dependence. The origin of the resonances of the $5f$ main line and the 2.3-eV satellite is discussed in an atomic framework taking $5f$ and $6d$ screening into account.