title: Tuning Charge Transfer in Ion-Surface Collisions at Hyperthermal Energies.
abstract: Charge exchange in ion-surface collisions may be influenced by surface adsorbates to alter the charge state of the scattered projectiles. We show here that the positive-ion yield, observed during ion scattering on metal surfaces at low incident energies, is greatly enhanced by adsorbing electronegative species onto the surface. Specifically, when beams of N(+) and O(+) ions are scattered off of clean Au surfaces at hyperthermal energies, no positive ions are observed exiting. Partial adsorption of F atoms on the Au surface, however, leads to the appearance of positively charged primary ions scattering off of Au, a direct result of the increase in the Au work function. The inelastic energy losses for positive-ion exits are slightly larger than the corresponding ionization energies of the respective N and O atoms, which suggest that the detected positive ions are formed by surface reionization during the hard collision event.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, 91125, USA.
authors.forename: Yunxi
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, 91125, USA. giapis@cheme.caltech.edu.
authors.forename: Konstantinos P
authors.identifier: 0000-0002-7393-298X
authors.initials: KP
authors.lastname: Giapis
keywords: gold; ion exchange; low-energy ion scattering; reionization; surface dynamics; work function