Theory of high-energy photoemission

Abstract

The angular distribution of emitted photoelectrons is theoretically studied for high-energy X-rays where electric quadrupole and magnetic dipole transitions are taken into account in addition to the electric dipole transition. We apply irreducible tensor expansion of photon field instead of usual power series expansion. The present numerical calculations show that the conventional power series expansion works so well up to quite high energy for the core excitation. We also discuss the recoil effects of nuclei associated with photoemission excited by high-energy X-rays, which gives rise to the energy shift and the peak broadening. For practical calculation we furthermore introduce Debye approximation for phonon spectra, which brings about the simple free atom recoil energy shift. In the simple Debye approximation we can expect no contribution to the broadening. © 2005 The Surface Science Society of Japan.