We investigate the convoy-electron (CE) emission produced during grazing bombardment of a Cu(100) surface with 20–100-keV protons. At 0.5° of incidence the CE peak measured at projectile energies below 50 keV along the direction of specular reflection of the ions presents the same width and shape as the CE peak corresponding to ${\mathrm{H}}^{+}$-He collisions and is considerably narrower than that observed in transmission through thin foils. This finding shows that CE’s are mainly subjected to the Coulomb potential of the scattered ion when the velocity resolutions are high enough to localize electron states close to the ion velocity. A strong variation of the CE peak shape with the projectile incidence angle was also observed. This finding can be explained by a calculation that takes into account the angular distribution of the reflected ions.

• Received 1 October 1991

DOI:https://doi.org/10.1103/PhysRevA.45.R1299