Measurement of the differential surface and volume excitation   probability of medium energy electrons in solids
  A procedure is developed to rigorously decompose experimental loss spectra of medium-energy electrons reflected from solid surfaces into contributions due to surface and volume electronic excitations. This can be achieved by analysis of two spectra acquired under different experimental conditions, e.g. measured at two different energies and/or geometrical configurations. The input parameters of this procedure comprise the elastic scattering cross section and the inelastic mean free path for volume scattering. The (normalized) differential inelastic mean free path as well as the differential surface excitation probability are retrieved by this procedure. Reflection electron energy loss spectroscopy (REELS) data for Si, Cu and Au are subjected to this procedure and the retrieved differential surface and volume excitation probabilities are compared with data from the literature. The results verify the commonly accepted model for medium energy electron transport in solids with unprecedented detail. 
Wolfgang S.M. Werner