Negative ion formation in the large energy backscatteringof H+ from HOPG

M. A. ROMERO; A. IGLESIAS-GARCÍA; F. BONETTO; R. VIDAL; E. C. GOLDBERG

Conferencia; 17 International Conference on Solid Films and Surfaces; 2014

The formation of negative ions in the scattering of protons by a highly oriented pyrolytic graphite (HOPG) surface is theoretically and experimentally analyzed for a large scattering angle and large incoming kinetic energies. 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 comparison with the experiment of the different limit approximations of the electronic repulsion in the atomic state, shows the expected validity ranges accordingly to the ion velocity. The importance of taking into account the density matrix of the solid in our description of the surface is analyzed within the spinless approximation of the Anderson hamiltonian. Nevertheless, the most remarkable conclusion obtained from this comparison is the non-validity of an adiabatic image of the energy levels shifted by the interactions with the surface atoms, when the energy uncertainty introduced by the ion velocity becomes of the order of the electronic repulsion in the hydrogen ground state.