Low-Energy Excitations inα- andγ-Ce Observed by Photoemission

Uv-photoemission spectra of the $\alpha$ and $\gamma$ phases of Ce have been measured with an unprecedented resolution (20 meV). A detailed many-body calculation based on the Anderson impurity model and including the $4f^1$ spin-orbit splitting has been performed. It accounts perfectly for the fine structures observed in the spectra. Within the energy range corresponding to the ground-state lowering by the $f-d$ hybridization, the $f$ contribution to the spectra reveals the density of low-energy excitations culminating at $E_{\mathrm{F}}$.