Negative ion formation in proton Ba/Ag(111) collisions: effects of the surface structure

Effects of the surface structure on H- scattering from clean and Ba covered Ag(111) are reported. The H-atoms are scattered from the surface as well as from deeper layers of the crystal. This is clearly seen in the angular distributions of the back scattered ions. The Ba atoms on the Ag(111) sit at lattice positions of the substrate. The layer contains vacancies to accommodate the large Ba atoms of the substrate.