Abstract
Using electron energy-loss spectroscopy at grazing incidence on graphite crystal, we have observed: (i) a strong dispersion-from 5 eV up to 19 eV-of the volume loss associated with an excitation direction parallel to the c axis and a wavevector greater than the Ferrel wavevector cut-off (2.1 AA-1< mod q/sub /// mod -1); (ii) a variation of the mean inner potential seem by the incoming electrons when the penetration depth is varied from 4 AA up to 7 AA; and (iii) the existence of two losses at 6.2 eV and 20.1 eV which may correspond to surface-plasmon excitations parallel to the layer surface.