6.2.2.1.3 Electron-hole pair and Stoner excitations

This chapter discusses electron-hole pair and Stoner excitations on metal surfaces. Measured and calculated energy loss probability in the tail of the specular peak for Cu(001) due to the electron-hole pair excitations is illustrated. An intense and structured background due to electron-hole pair excitations was observed on Ni(110). The modulation is due to the rapid variations of an elastic reflectivity connected with low-energy electron diffraction (LEED) fine structure. Electron energy loss spectrum (EELS) at various primary energies is plotted as a function of the kinetic energy of the scattered electrons. On Ni(001) a minimum in an inelastic background was reported for energy losses below the onset of interband transition. The structure becomes fainter at high temperatures but is still present above the Curie temperature. The energy loss processes, which contribute to the inelastic intensity, are shown. Spin polarized electron energy loss (EEL) spectra for Ni(110) is plotted. Schematic representation of two-electron inelastic scattering processes with the spins included is given. Total EEL-intensity for spin polarized electron scattering off Fe(110) is illustrated. For Fe a spin polarization was measured for both the incident and the scattered electrons. Partial and total intensity asymmetries of Fe corrected for the partial degree of spin polarization of an impinging beam are presented. EEL-spectra of graphite is measured in-specular at different temperatures of a sample showing a loss due to the excitation of the π-band plasmon. Plasmon frequency and width in graphite vs. crystal temperature of graphite are plotted.