AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP9
The Effect of Water Vapor on the Surface Composition of Alkali Halides

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: S. Ghosal, University of California, Irvine
Authors: S. Ghosal, University of California, Irvine
F.G. Requejo, University of La Plata and CONICET., Argentina
D.F. Ogletree, Lawrence Berkeley National Laboratory
M. Salmeron, Lawrence Berkeley National Laboratory
J.C. Hemminger, University of California, Irvine
Correspondent: Click to Email
We present here results from our studies on the aqueous ionic solvation of alkali halide surfaces. Using a novel high pressure X-ray Photoelectron Spectroscopy (XPS) system based on the ALS synchrotron radiation source we have for the first time made dire ct experimental measurements of the surface composition of alkali halide crystals while in contact with water vapor pressures approaching and at the point of dissolution. The salt crystals were cleaved in vacuum and then analyzed by XPS as the water vapor pressure was increased. Our results show that the anion/cation ratio at the interfacial region initially decreases with increasing water vapor pressure. At higher water vapor pressures, approaching the dissolution point of the salt, the surface compositi on behavior varies depending on the particular salt. These results are further supported by Scanning Polarization Force Microscopy experiments. The primary focus of the study was to determine the structure and composition of the interfacial region between the salt and air as a function of water vapor exposure. This is of particular interest since the solid/vapor interfacial composition of salt solutions and salt particles has implications for heterogeneous atmospheric chemistry involving sea salt aerosols.@footnote 1@ @FootnoteText@ @footnote 1@Finlayson-Pitts, B. J.; Hemminger, J. C. J. Phys. Chem. 2000, 104(49), 11463.