REASSESSMENT OF ENERGY TRANSFERS IN THE QUASI-ELASTIC SCATTERING OF 250-3000 EV ELECTRONS AT SURFACES

Measurements are reported of the quasielastic scattering energy losses of electrons of 250-3000 eV from clean Cu, Ag, and Au in order to ver ify the large loss values recently observed by Erickson and Powell. La rge loss values, if they were valid, would lead to a range of interest ing analytical possibilities. However, here it is shown that the losse s are small and are in agreement with the single-particle scattering m odel of Boersch et al. A null method is used which allows the energy o f the unscattered beam to be referenced at each energy so that the ene rgy losses may be determined directly with an accuracy of 15 meV. It i s concluded that the measurements in the study of Erickson and Powell may have included a contribution from the cathode supply circuit that increased as the energy increased. The very low values of the losses o bserved here are predicted to be significant in surface analysis only for scattering from elements with atomic numbers less than 20.