Energy-Dependent Photoemission Intensities of " f " States in EuS, GdS, and US

Photoemission measurements of f states and valence-band energies of EuS, GdS, and US for photon energies from 5 to 41 eV show characteristic energy-dependent emission strengths of "p," "d," and "f" states. These energy dependences permit the "l" character of various levels to be identified in many cases. For example, the emission strength of the 4f⁷ level in EuS increases about 100-fold relative to the 3-eV wide valence "p" band which lies just below the 4f⁷ level. GdS shows a deep 4f⁷ level at about 9 eV below the Fermi level EF, and US shows an "f-d" band at EF.