Electron screening and electron-electron scattering mechanisms

The roles of binary and multiple scattering are considered in the context of electron scattering and diffraction on the W(1 1 0) and W(1 1 0) + O(1 × 1) surfaces for energies from 10 to 40 eV. We define a binary scattering mechanism as the incident electron interacting with the field of a valence electron with conservation of the total momentum of the incident and valence electrons. Multi-particle scattering is defined as an interaction of the incoming electron with superposed valence electron fields where determination of the total momentum is not well described. The scattering mechanisms all depend on the electron energy, the density of the scattering electrons and the screening parameter of the Coulomb field in the solid. A model is suggested for the formation of the potential of the scattering field as a superposition of the fields of the screened valence electrons uniformly situated over the first coordination sphere. A quantitative criterion is developed for the binary scattering in which the radial distribution of the scattering potential is normalized to a single charge potential distribution. The model predicts an electron binary scattering mechanism from clean W(1 1 0) and a multi-particle scattering mechanism from W(1 1 0) + O(1 × 1). The results agree with experimental results and imply the validity of the modeled assumptions. The model also shows for electron-pair (e,2e) spectroscopy on metals that the electron-electron interaction occurs predominantly in the vicinity of an atom associated with the diffraction of the incident electron.