Signals of strong electronic correlation in ion scattering processes.

FERNANDO BONETTO; E. C. GOLDBERG

Playa del Carmen

Taller; VIII Taller de Colisiones Inelásticas en la Materia; 2016

Universidad Autónoma de Mexico.

Previous measurements of neutral atom fractions for Sr+ scattered by goldpolycrystalline surfaces show a singular dependence with the target temperature. There is still no a theoretical model that can properly describe the magnitude and the temperature dependence of the neutralization probabilities found. Here we applied a first-principles quantum mechanical theoretical formalism to describe the time dependent scattering process. Three different electronic correlation approaches consistent with the system analyzed are used: i- Spinless approach, where two charge channels are considered (Sr0 and Sr+) and the spin degeneration is neglected, ii- infinite-U approach, with the same charge channels (Sr0 and Sr+) but considering the spin degeneration, and iii- finite-U approach, where the first ionization and second ionization energy levels areconsidered very but finitely separated. Neutral fractions magnitudes and temperature dependence are better described by the finite-U approach indicating that e-correlation plays a significant role on charge transfer processes. However, none of them are able to explain the non-monotonous temperature dependence experimentally obtained. Here, we suggest that small changes in the surface work function introduced by the target heating, and possibly not detected by experimental standard methods, could be responsible of that singular behavior. Additionally, we apply the same theoretical model using the infinite-U approximation to the Mg-Au system, obtaining an excellent description of the experimental neutral fractions measured.