Intensity singularities in the soft x-ray appearance potential spectra of the samarium N5 and M5 levels

Abstract

We have obtained soft x-ray appearance potential spectra of the N and M levels of samarium metal by scanning the electron excitation energy from 50 through 1560 eV. Newly observed line-like x-ray emission singularities are identified for excitation energies near the ionization potentials of the N5 and M5 levels. The excitation of the singularities depends upon both the energy of the incident electron and the angular momentum of the core state vacancy. The singularities are attributed to final state interactions between the inner vacancy and a two-electron bound state at the site of the core vacancy.