CORE EXCITATIONS AND SECONDARY-ELECTRON SPECTRA OF CU(100)

Electronic transitions near the 2s, 2p, 3s and 3p edges of Cu(100) are investigated with electron energy loss spectroscopy and compared with real-space multiple-scattering calculations that take into account the momentum transfer q in the electron scattering process. The interplay between q and the different angular momentum channels involved in the transitions show that while for the 2p-edge with a large energy loss (and with a large q) dipole transitions dominate the spectrum, the non-dipole channels are very strong for the 3s-edge even with small q. The methods are extended to scattering states up to 300 eV above the Fermi level in order to identify structures in the secondary electron emission spectra. The strength of electron energy loss spectra in reflecting the electronic structure of solid surfaces is emphasized along with the necessity of a complete theoretical analysis before the dipole approximation may be applied.