ENERGY-LOSS SPECTRA OF H-COVERED PD SURFACES( AND HE+ SCATTERED OFF CLEAN AND K)

In the last years we studied the energy loss of low-energy (0.5-5 keV) particles incident under grazing incidence on metal surfaces for some simples systems, e.g. He and H on Ni and Pd surfaces [H. Derks et al. , Nucl. Instr. and Meth. B44 (1989) 125, A. Narmann et al., Phys. Rev. Lett. 64 (1990) 1601, A. Narmann et al., Nucl. Instr. and Meth. B69 ( 1992) 158). The detector is placed in specular direction. In this way we only probe the surface region. We want to investigate the effect on energy loss when using systems with different electronic structure. T his was performed by depositing layers of potassium onto a metal surfa ce and thereby varying the electron density at the surface. The questi on is, how can we explain the experimental results, which description of the surface properties does fit the experimental results best?