Extreme Ultraviolet Absorption Spectra of Barium and Rare Earth Metals

Abstract

Optical absorption spectra of Ba and rare earth metals have been measured over the photon energy range from 10 to 40 eV. The spectra for Ba do not show Fermi edge singularity as observed in Cs metal. It is found that the energy broadening of the 5p absorption threshold depends systematically on the atomic number and particularly on the number of 4f electrons. It is suggested that the potential of the photo-produced 5p hole induces the virtual localization of 5d electrons and this enhances the interaction between 5d and 4f electrons appreciably.