Correlation effects in neon studied by elastic and inelastic high-energy electron scattering

The elastic and inelastic differential cross sections of 35-keV electrons incident on Ne were measured in the momentum-transfer range of 1–10 a.u. (20–200 mrad). The accuracies maintained throughout the experiment were 0.2% for the elastic scattering intensities and 2’ ’ for the scattering angles. The diffraction unit is discussed. The elastic data are compared with partial-wave cross sections based on several atomic wave functions (Hartree-Fock, configuration-interaction, and independent-electron-pair approximation). None of the theoretical results coincides with the data within the error limits over the whole measured angular range. The large-angle results show very small deviations from the calculated cross sections and so this range is used to bring the measured cross sections to an absolute scale. The elastic, inelastic, and total cross sections were integrated and several potential energies were evaluated. The differences between the measured potential energies and the Hartree-Fock results reveal the importance of correlation for the electron-nuclear potential $V_{\mathrm{ne}}$ and the electron-electron potential $V_{\mathrm{ee}}$ which in turn can be decomposed into $V_{\mathrm{ee}}$(Coulomb) and $V_{\mathrm{ee}}$(exchange) parts.