Charge exchange in H-Cu(111) low energy collisions

RICARDO A. VIDAL; MARCOS TACCA; EDITH C. GOLDBERG; V. QUINTERO RIASCOS; FERNANDO BONETTO

Armação dos Búzios

Congreso; XL Encontro Nacional de Física da Matéria Condensada; 2017

Sociedad Brasilera de Física

The formation of positive and negative ions in the scattering of protons by a Cu(111) surface is theoretically and experimentally analyzed for a large scattering angle in a backscattering geometric configuration. Low EnergyIon Scattering (LEIS) technique was used to measure the ion fractions in the collision, where a peculiarly high yield of negative ions are detected for the whole energy range analyzed (from 2 to 8keV) A first principlesquantum-mechanical formalism is applied to describe the charge transfer produced in low energy collisions between a H+ incident ion and the Cu(111) metallic surface. All the physical ingredients involved on thedynamic problem analyzed, such as the crossed terms of the density matrix of the surface solid, the number of surface atoms considered, and the change in the energy level and its width relative to the target surface Fermilevel are discriminated and its influence on the partial and final charge states are thoroughly examined. The contrast between theoretical and experimental data allows us to infer how relevant are the different physicalingredients included in the model and the energy range where they play a significant role. According to our findings we can conclude that: i) the projectile charge state is mainly defined on the exit trajectory, beingthe final part of the trajectory specially relevant for lower energies; ii) the inclusion of the crossed terms of the density matrix introduces a significant change on the projectile energy level and width, leading to relevantchanges in the neutralization curve on the whole range of incoming energies and iii) the introduction of a large number of surface atoms to describe the solid target is crucial to explain the the large negative ion fraction experimentally observed.