New results will be presented concerning the interpretation of energy-loss spectra obtained after light particle (H, He) scattering at low energies (E_0 chemical bounds some keV) and grazing incidence off clean and alkali-covered metal surfaces. The metal surface is described by an electron gas with decaying density perpendicular to the surface. BY applying a simple model the spectra can be used in order to extract information about the electron density distribution at the surface. It turns out that at surfaces there is an additional contribution to the stopping power that is not present if one considers interaction with a homogeneous electron gas of constant density.
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