Elastic and inelastic electron mean free paths from x-ray photoelectron diffraction experiments

Abstract

Angle-resolved detection of Pb4f72 photoelectrons from a Pb(110) crystal was used in conjunction with deposited K overlayers to determine the elastic and inelastic mean free paths of electrons at 1345 eV energy in K. The angle-resolved 4f72 intensity distribution along the [11̄0] azimuth showed large forward scattering enhancements whose attenuation by K overlayers was evaluated to yield an effective electron mean free path of 7.0 ± 1 Å. The inelastic and elastic mean free paths in K were determined as 45 ± 5 and 8 ± 4 Å, respectively. The high cross section for elastic scattering makes angle-resolved XPS (or Auger spectroscopy) a much more sensitive tool for detecting small coverages of adsorbates than its angle-integrated counterpart.