Does EELS haunt your photoemission measurements

Photoemission has been used for years as a reliable technique for probing the the electronic structure of the occupied states in solids ranging from insulators through semiconductors and metals to superconductors. In his article Joynt provided very convincing and interesting arguments that especially for badly conducting samples (roughly ρ0 � 0.1mcm, the Mott value) the photoelectron spectrum may be affected by energy loss structures resulting from the interaction with the time dependent fields set up by the photoelectron receding from the surface of the solid. He argued that the influence of these loss processes can be so strong that the spectrum is dominated by them and that therefore the intrinsic information regarding the electronic structure of the solid all but disappears. Since photoemission is playing such a prominent role in the discussion of strongly correlated materials like the High Tc’s, or more generally the transition metal oxides, as well as in Kondo and Heavy Fermion systems, it is of quite some importance to further investigate Joynt’s assertions. In this paper we study Joynt’s arguments and provide both experimental and theoretical findings that show that the effects due the losses discussed by Joynt are only a small contribution to the total spectrum and the zero energy loss probability for the photoelectrons dominates for samples of either good or bad conductivity.