Kinetic energy distributions of C+, C2+, Au+, AuC+ and AuC2+ emitted from a gold surface following single impact of keV C60-: Carbide ions formation via a recombination mechanism

We have studied the formation and emission of small carbide cluster ions AuC+ and AuC2+ following reactive ion shattering of 10 keV C60- on gold. We have measured kinetic energy distributions of several outgoing cations (C+, C2+, Au+, AuC+ and AuC2+) and found pronounced differences between these of the carbon fragments ions and carbide ones, with broad C+, C2+ distributions peaking at ∼11 eV and much narrower AuC+, AuC2+ distributions peaking at ∼2-3 eV. Density functional theory calculations of the AuC2+ cation have shown that the two most stable isomer structures are composed of a carbon dimer strongly bound to a gold ion. Analysis of the kinetic energy distributions transformed into speed distributions, together with the calculated structures, suggest that the formation of the carbide cluster ions (AuC+, AuC2+) is via a recombination between independently emitted, moving gold and carbon species, within the surface vicinity.