ANGLE-RESOLVED EMISSION OF LOW-ENERGY ELECTRONS IN GRAZING COLLISIONSOF PROTONS WITH AN AL(111)-SURFACE

Angle-resolved energy spectra of electrons emitted during the collisio n of 10 to 29 keV protons with a clean and flat Al(111)-surface under grazing incidence are reported. We observe in the electron energy regi me of our studies (0 to 60 eV) two broad peak structures. A low-energy peak, tentatively ascribed to secondary-electron-emission processes, and an emission at higher energies peaked in forward scattering direct ion. We interpret the latter finding in terms of a direct-kinetic-elec tron-emission mechanism; i.e. direct ejection of conduction electrons into vacuum via collisions with the projectiles.