Photoemission Studies of f States and Valence Bands in Several Rare-Earth and Uranium Compounds

Photoemission spectroscopy measurements of f states and valence band energies are reported for EuS, GdS, and US using photon energies for 5 to 41 eV. The energy dependence of photoemission spectra permits the ``l'' character of various levels to be identified. Characteristic energy-dependent emission strengths of ``p'', ``d'', and ``f'' states are observed. In a typical case, the emission strength of the 4f7 level in EuS increases about 100-fold relative to the ∼2.9-eV-wide valence ``p'' band (which lies just below the 4f7 level) as ℏω increases from 10 to 41 eV. Metallic GdS shows a ``d''-like conduction band at the Fermi level EF, a 4.5-eV-wide ``p''-band centered at ∼5 eV below EF, and a 4f7 level at 9 eV below EF. Uranium monosulphide shows a narrow ``f-d'' conduction band at EF and a 4.7-eV-wide ``p''-band centered at 4.7 eV below EF.