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Abstract:
The surface extended energy loss fine structure (SEELFS) technique has been used by various authors to investigate metal surfaces, metallic interfaces, adsorbates and clusters.
In the present work, Cu(110) and (111) surfaces were investigated using different primary energies in order to study the validity of the dipole approximation and the plane-wave approximation of this technique.
The calculated differential cross sections of different l transitions show that non-dipole transitions in the case of the Cu M2,3 must be taken into account; their respective SEELFS spectra were calculated.
A shift of the first peak in the radial distribution functions (RDF) of copper depending on the primary energy was observed, which can be explained by the change of the total effective phase shifts caused by a variation of the relative intensities of the differential cross sections of the different transitions. The shift of the first peak in the RDF of the Cu(110) surfaces compared to that of the Cu(111) surfaces is likely to be due to the surface relaxation of copper. The nearest-neighbour distance of copper, evaluated from the SEELFS spectra by using the curved-wave approximation, the calculated differential cross sections and the calculated phase shifts, agrees well with the bulk value. The use of the plane-wave approximation leads to an apparent lattice contraction.
