The relevance of atom excited configurations in the scattering of positive helium ions by metallic surfaces.

E. C. GOLDBERG

Debrecen

Conferencia; ? 26th International Conference on Atomic Collisions in Solids; 2014

The relevance of atom excited configurations in the scattering of positive helium ions by metallic surfaces. E. C. Goldberg1 1IFIS Litoral (CONICET-UNL); Guemes 3450 (3000) Santa Fe, Argentina. Corresponding author: edith.goldberg@santafe-conicet.gov.ar The final charge states of ions scattered by a surface as well as the associated electron emission provide abundant information about the details of the surface electronic band structure and the interacting atoms correlated states [1-2]. This fact has motivated the development of new theoretical proposals that, following feedback with experimental data, allow for a deep understanding of the physical mechanisms underneath. This is the case of the large angle scattering of positive helium ions by metallic surfaces such as Al(100) and HOPG (highly oriented pyrolytic graphite). The high ion neutralization and the high energy electron emission observed in both ion-surface interacting systems can not be explained by assuming the helium ground state as the only one involved in the charge exchange process. We find that the experimental results can be reproduced by our theory if we take into account the electronic correlation introduced by the He first excited states also considered as possible neutralization channels [3]. By the other hand, the finite occupation of these excited states opens the Auger de-excitation process as a source of emitted electrons [4]. The excited configurations of He atom with an appreciable probability of occurrence are included by projecting the extended Anderson Hamiltonian over the selected configuration space; and the dynamical evolution of the interacting system is solved by using the Green-Keldysh functions and the method of motion equations. In the case of He+/HOPG we con-sider only the resonant charge exchange mechanism while in the case of He+/Al we include the resonant and Auger mechanisms acting together along the time dependent evolution of the scattering process. We finally show that the correlation between the ground and excited atomic configurations notably strengthen the neutralization to the ground state. References [1] N. Bajales, L. Cristina, S. Mendoza, R. A. Baragiola, E. C. Goldberg, and J. Ferrón, Physical Review Letters (2008) 100, 227604. [2] N. Bajales, J. Ferrón, and E. C. Goldberg, Physical Review B (2007) 76, 245431. [3] A. Iglesias-García, E. A. García, and E. C. Goldberg, Physical Review B (2013) 87, 075434. [4] A. Iglesias-García, F. Bonetto, R. Vidal, J. Ferrón, and E. C. Goldberg, Physical Review A (2013) in press.