Electron excitations in grazing diffraction of fast He on a Ag(1Â 1Â 0) surface. A tribute to Hannspeter Winter

Grazing incidence diffraction of fast atoms (GIFAD) on surfaces has first been discovered on ionic insulators where electronic excitations are strongly reduced due to the large band gap. At variance no threshold exists for electronic excitations close to the Fermi edge of a metal surface. New results of energy resolved diffraction of keV helium atoms on a Ag(1 1 0) surface are presented which considerably extend the application range of GIFAD. The combined analysis of the energy loss and diffraction data could help providing a detailed description of the collision of helium with the surface electrons.