AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Invited Paper SS2-TuM5
2006 Medard W. Welch Award Lecture - Surface Composition and Surface Chemistry of Alkali Halide Solids and Aqueous Solutions

Tuesday, November 14, 2006, 9:20 am, Room 2004

Session: Water-Surface Interactions
Presenter: J.C. Hemminger, UC, Irvine
Authors: J.C. Hemminger, UC, Irvine
M.J. Krisch, UC, Irvine and AirUCI
M.A. Brown, UC, Irvine and AirUCI
S. Ghosal, LLNL
H. Bluhm, LBNL
B.S. Mun, LBNL
A. Verdaguer, Institut Catala de Nanotecnologia, Spain
F. Ogletree, LBNL
M. Salmeron, LBNL
Correspondent: Click to Email
Chemistry at the surfaces of aerosol particles in the troposphere has become a topic of considerable interest recently. Reactions between gas phase molecules in the atmosphere and aerosol particles and droplets may modify the properties of the aerosol (such as hydrophobicity or chemical composition). In addition, components of the aerosol may be converted into volatile compounds that can then be active in gas phase reactions in the troposphere. Clearly, the composition of the surfaces of such particles will control their surface reactivity. We have studied models for sea salt aerosols, which are abundant in the marine region world-wide. We have shown that adsorbed water is critical to the surface chemistry of salt surfaces. In addition, recent molecular dynamics simulations of alkali halide solutions have suggested that the surfaces of alkali halide solutions are enriched in halide species. Our experiments quantitatively confirm that the surfaces of aqueous KI, KBr and KCl solutions have enhanced halide ion concentrations. Additionally, experiments on Br doped NaCl samples show conclusively that Br strongly segregates to the liquid-vapor interface of such mixed solutions. A combination of data from scanning polarization force microscopy experiments and x-ray photoelectron spectroscopy experiments will be shown to illustrate these phenomena. The importance of these results to atmospheric chemistry will be illustrated through a discussion of bromine segregation in sea salt aerosols and the importance of the subsequent bromine chemistry in the arctic marine troposphere.