Electron-energy-loss spectroscopy and oxygen overlayers on the Ni(100) surface

We present an analysis of the electron-energy-loss spectra produced by dipole scattering from lattice vibrations of the p(2 x 2) and c(2 x 2) oxygen overlayer on the Ni(100) surface. We conclude that the distance between the oxygen layer and the Ni surface is very much smaller for the c(2 x 2) overlayer than for the p(2 x 2), in accord with a recent suggestion by Upton and Goddard