  In the light of recent measurements of the C 1s core level dispersion in
graphene [Nat. Phys. 6, 345 (2010)], we explore the interplay between the
elastic scattering of photoelectrons and the surface core level shifts with
regard to the determination of core level binding energies in Au(111) and
Cu3Au(100). We find that an artificial shift is created in the binding energies
of the Au 4f core levels, that exhibits a dependence on the emission angle, as
well as on the spectral intensity of the core level emission itself. Using a
simple model, we are able to reproduce the angular dependence of the shift and
relate it to the anisotropy in the electron emission from the bulk layers. Our
results demonstrate that interpretation of variation of the binding energy of
core-levels should be conducted with great care and must take into account the
possible influence of artificial shifts induced by elastic scattering.
