Charge transfer in low-energy collisions of protons with a thick C60 film.

R. VIDAL; M. TACCA; F. BONETTO; V. QUINTERO RIASCOS; E. C. GOLDBERG

Aracaju, Brasil

Encuentro; Autumn Meeting of the Brazilian Physical Society; 2019

Sociedade Brasileira de Fisica

Charge exchange process in collisions between H+ projectiles and a 3 monolayer C60 film grown on Cu(111)are experimentally and theoretically analyzed for a wide range of energies (2-8keV) in the low-energy regime.Experimentally, the negative, positive and total projectile scattered fractions are determined by using the low energy ion scattering (LEIS) technique. Two di®erent collisional setups were studied for a fixed backscatteringangle of 135o: 45o/90o and specular 67.5o/67.5o incoming/exit angles determined with respect to the target surface plane. Total ion fractions between 10% and 20% are experimentally found in the whole energy range analyzed, with a slight but consistent increase with the projectile incoming energy. Positive ions were measured to be the majority of the total scattered charged projectiles in almost the whole energy range analyzed. Only for very low incoming energies (2-3 keV), the positive and negative ion fractions become comparable. A first-principles based theoretical model was used to describe the dynamic charge exchange processes taking place in the experimental collisional situation. A very good description of the experimental results is obtained in the whole studied energy range. Theoretical and experimental results are also analyzed in comparative terms with our previous measurements in the H+/pyrolytic graphite (HOPG) system, where similar, but not identical, results were obtained. Slight differences in the ion fractions obtained can be directly related to differences in the electronic structure of C60 and HOPG.