AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP31
Charge Exchange between Alkali Ions and Cerium Oxide Surfaces

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: G. Liu, University of California, Riverside
Authors: G. Liu, University of California, Riverside
J. Yarmoff, University of California, Riverside
Correspondent: Click to Email
CeO@sub 2@ has interesting catalytic properties, which are presumably the result of an electronic configuration that includes many valence electrons. Earlier, we showed that the probability for neutralization of low energy alkali ions scattered from metal surfaces is determined by resonant charge transfer (RCT) along the exit trajectory, and it depends on the local electrostatic potential (LEP) a few Å's above the scattering site.@footnote 1@ We also showed that RCT is effected by localized confined states in nanomaterials.@footnote 2@ The present work investigates the charge exchange between alkali ions and cerium oxide surfaces. The neutral fractions of 3 keV @super 23@Na@super +@ ions singly scattered from the Ce sites on CeO@sub 2@ single crystal surfaces were measured with time-of-flight spectroscopy. The angular dependence of the neutralization was found to be isotropic for CeO@sub 2@(111), while for CeO@sub 2@(100) the neutralization decreases for more grazing angles. The results from either surfaces cannot be explained by simple RCT theory, which predicts increased neutralization at grazing angles, and may therefore suggest that a new mechanism for charge transfer is operative with these materials. In order to ascertain the influence of the work function on ion neutralization, Cs and Br were deposited onto the CeO@sub 2@ surfaces to controllably decrease and increase the work function, respectively. Results for scattering from CeO@sub 2@(100) and CeO@sub 2@(111) will be compared and contrasted. @FootnoteText@ @footnote 1@C. B. Weare and J. A. Yarmoff, Surf. Sci. 348 (1996) 359.@footnote 2@G. F. Liu, Z. Sroubek and J. A. Yarmoff, Phys. Rev. Lett., in press. .