Negative ion formation in the large energy backscattering of H+ from HOPG.

EDITH C. GOLDBERG; MARCELO A. ROMERO; ADALBERTO IGLESIAS-GARCÍA; FERNANDO BONETTO; RICARDO VIDAL; JULIO FERRON

Ntal

Congreso; I Congreso Iberoamericano de Superficies, Materiales y Aplicaciones de Vacio; 2014

The formation of negative ions in the scattering of protons by highly oriented pirolytic graphite (HOPG) surface is theoretically and experimentally analyzed for large kinetic energies of the incoming proton. The open questions related with the electronic correlation effects and the influence of the detailed surface band structure are tried to be answered by using appropriate theoretical proposals. The importance of taking into account the density matrix of the solid in our description of the surface is analyzed. The comparison between the experimental results and the calculations including different limit approximations of the electron-electron interaction in the localized atomic state shows the expected validity ranges accordingly to the ion velocity. Nevertheless, the most remarkable conclusion obtained from this comparison is the non-validity of the adiabatic calculation of the energy level shift when the energy uncertainty introduced by the ion velocity becomes of the order of the electronic repulsion in the hydrogen ground state.