Measurement of the4f-shell optical edge in Gd metal

Vacuum-ultraviolet absorption techniques are used to study $4f$-shell optical excitations in Gd metal. The results provide insight into the discrepancy between $4f$-shell excitation thresholds reported from x-ray absorption and x-ray photoemission studies. The different threshold energies are attributed to different screening configurations in the final states, or to spurious shifts of the x-ray photoemission peaks.