M 2,3 electron energy loss studies of Ni(100) at small scattering angles

Reflection electron energy loss spectra of a Ni (100) surface in the region of M2,3 ionization have been recorded at small scattering angles. Extended fine structure in the continuum (EXELFS) is analyzed to yield an estimate of the nearest neighbor distance in the surface region. These results are compared to previous surface M2,3 EXELFS of polycrystalline Ni recorded with lower energy and angle resolution at large scattering angles.  When calculated M2,3 phase shifts are used the derived spacings in both the large and small angle data are about 0.3 Å less than the value for the Ni–Ni spacing in bulk Ni. This indicates that the deviation results from errors in the phase shift rather than nondipole contributions in the large scattering angle data.