Does EELS haunt your photoemission measurements?

Abstract

It has been argued in a recent paper by R. Joynt (R. Joynt, Science 284, p 777 (1999)) that in the case of poorly conducting solids the photoemission spectrum close to the Fermi Energy may be strongly influenced by extrinsic loss processes similar to those occurring in High Resolution Electron Energy Loss Spectroscopy (HR-EELS), thereby obscuring information concerning the density of states or one electron Green's function sought for. In this paper we present a number of arguments, both theoretical and experimental, that demonstrate that energy loss processes occurring once the electron is outside the solid, contribute only weakly to the spectrum and can in most cases be either neglected or treated as a weak structureless background.