High-energy spectroscopy of fn+1 and fn−1 states in rare earth metals

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Abstract
Two different spectroscopies have been used to study the 4f shell in rare earth metals. The spectra obtained by X‐Ray Photoemission Spectroscopy (XPS) reflect the final states resulting from the transitions fn→fn−1; in Bremsstrahlung Isochromat Spectroscopy (BIS) the recorded intensity of x‐rays accounts for the transitions fn→fn+1. The analysis of the two types of spectra of one element with initial configuration 4fn yields an exact determination of the excitation energies Δ− and Δ+ to the ground states of fn−1 and fn+1. The experimental energies are related to EF and correspond to completely screened final states of the metals. (Δ+−Δ−) can be interpreted as the screened Coulomb correlation energies U which is very large in these metals (5–12 eV) and prevents the formation of a band.