Energy loss functions for electron energy loss spectroscopy

Losses to surface excitations affect experimental data in several different kinds of spectroscopies and have been considered in detail by various work ers. We discuss and compare calculations using commonly assumed response fu nctions. The boundary (begrenzung) effect, originating in the orthogonality of surface and bulk eigenmodes, manifests interesting interference in the loss functions. The variation of static electron density in the selvage of a metal is known to affect the dispersion of surface excitations. The effec t of this structure on energy loss spectra is studied. Analytical forms of the kind studied can be employed in practical data analysis if parameterize d to correspond with more rigorous, but time-consuming, numerical results s uch as those found from density functional methods. (C) 1999 Elsevier Scien ce B.V. All rights reserved.