Surface excitation parameter for selected polymers

The surface excitation parameter (SEP) is theoretically determined for different polymers, namely, polyethylene (PE), polystyrene (PS), polyacetylene (PA) and polymethyl methacrylate (PMMA), for electron energies between 300 and 5000 eV and for angles between 0 and 70^o to the surface normal. We use our previous definition of SEP as the change in excitation probability of an electron caused by the presence of the surface in comparison with an electron moving in an infinite medium. The calculations are performed within the dielectric response theory by means of the QUEELS‐ε(k, ω)‐ REELS software determining the energy‐differential inelastic electron scattering cross‐sections for reflection‐electron‐energy‐loss spectroscopy (REELS). More precisely, the volume component for an infinite medium is subtracted from the calculated REELS cross‐section and in this way the surface excitation component of the cross‐section is determined and the SEP calculated. We find that the presence of an energy band gap reduces the SEP values compared to those for metals, and this decrease is larger for polymers with larger gaps. Copyright © 2008 John Wiley & Sons, Ltd.