UPS investigation of Fe single crystals

Abstract
UPS spectra of (111), (100) and (110) faces of Fe single crystals have been measured at normal electron emission, with HeI (21.2 eV) and HeII (40.8 eV) radiation. The spectra are very similar indicating that one is measuring a density of states rather than direct transitions. The reasons for this behaviour which contrast with that found in the noble metals and Ni are discussed.