Atomic near-degeneracy for photoemission: Generality of 4f excitations

In a previous study of the 3s X-ray photoelectron spectra, XPS, of Mn, we identified a new intra-atomic many-body effect that lead to an ∼50% increase in the predicted exchange splitting of the main high spin and low spin XPS peaks. The new many-body effect involved the promotion of one electron from the M shell, 3s, 3p, and 3d, into a 4f orbital and a redistribution of the remaining electrons over the M shell orbitals; of particular importance were frustrated Auger configurations. FACs where the 3s shell was filled. In the present work, we demonstrate the general importance of these 4f FACs by showing that they are of comparable importance for increasing the 3s exchange splitting in Ni as they were in Mn.