Charge Exchange in H+- Graphite Collisions: leading role of Time-Energy Uncertainty

FERNANDO BONETTO; M. A. ROMERO; A. IGLESIAS-GARCÍA; RICARDO VIDAL; EDITH C. GOLDBERG

Foz de Iguazú

Congreso; XXXVIII Encontro Nacional de Física da Matéria Condensada; 2015

Sociedad Brasilera de Física

The formation of positive and 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 in a backscattering geometric configuration. These ion fractions are contrasted with previous results obtained using a forward scattering geometry. Low Energy Ion Scattering (LEIS) technique was used to measure the ion fractions involved.The choice of the projectile-target system was motivated by the fact that the interaction of a hydrogen atom with a surface is the prototype system to study the intra-atomic Coulomb repulsion in an s-like valence orbitallocalized in the atom. We tried to answer the open questions related to the electronic correlation effects and the influence of the detailed surface band structure by using appropriate theoretical models. The theoretical-experimental data assessment allows us to infer how relevant are the different physical ingredients included in the model and the energy range where they play a significant role. The most remarkable conclusion obtained from this comparison is the non-validity of an adiabatic representation of the projectile energy levels (shifted bythe interactions with the surface atoms), when the energy uncertainty introduced by the ion velocity becomes of the order of the electronic repulsion.