Low Energy Electron Exchange Excitation of 4f Transitions and Location of 4f Levels in Rare Earths

Eu, Gd, and Tb single crystal films and atomically dispersed layers adsorbed on W(110) surfaces are studied by low energy electron loss spectroscopy. A very sharp dominant loss peak at about 4 eV is analyzed in detail and attributed to spin exchange excitation of the 4f level. This interpretation agrees very well with self‐consistent spin‐polarized free atom and band structure calculations. The results are compared with XPS and other experimentel data which leads to a reconsideration of the interpretation of the 4f XPS binding energies.