Extended energy loss fine structure in reflection electron energy loss spectra of Cu and Ni

Reflection electron energy loss spectra of the surfaces of polycrystalline Cu, Ni and Al have been recorded with impact energies ranging from 300 to 2400 eV. Weak structures observed in the M- and L-shell continua of Cu and Ni are interpreted as extended energy loss fine structure (EXELFS), the electron scattering analog of EXAFS. The nearest neighbour spacings derived from the M23 EXELFS are 0.2 to 0.3 Å less than the values for bulk Cu or Ni. This difference is attributed at least in part to the inaccuracy of calculated phase shift corrections rather than a surface contraction of this magnitude. Complications to reflection EXELFS from multiple plasmon losses are demonstrated in the aluminum L23 spectrum.