AVS 51st International Symposium
    Surface Science Friday Sessions
       Session SS1-FrM

Paper SS1-FrM7
Interfacial Segregation of Halogen Ions in Alkali Halide Solutions

Friday, November 19, 2004, 10:20 am, Room 210B

Session: Hydrated Surface Phenomena
Presenter: S. Ghosal, University of California, Irvine
Authors: S. Ghosal, University of California, Irvine
B.S. Mun, Lawrence Berkeley National Laboratory
D.F. Ogletree, Lawrence Berkeley National Laboratory
M. Salmeron, Lawrence Berkeley National Laboratory
J.C. Hemminger, University of California, Irvine
Correspondent: Click to Email
In recent years Molecular Dynamics (MD) Simulations@footnote 1, 2@ of alkali halide solutions have predicted the surface segregation of polarizable halogen ions. This is of particular interest since the composition of the liquid/vapor interface of salt solutions has implications for heterogeneous atmospheric chemistry involving sea salt aerosols@footnote 3@. We present here results from our studies of the surface composition of saturated salt solutions. Using a novel high pressure photoelectron spectroscopy (HPPES) system at beamline 9.3.2 of the ALS synchrotron radiation source, we have compared the surface composition of KBr and NaCl crystals cleaved in vacuum with the surface composition of the saturated solutions formed at the deliquescence point, in equilibrium with water vapor. Our results show that the anion/cation ratio in the saturated solution is significantly enhanced within one nanometer of the surface. This is consistent with the predictions of Jungwirth et al@footnote 1, 2@ regarding halogen surface segregation. @FootnoteText@ @footnote 1@ Jungwirth, P.; Tobias, D. J. J. Physical Chemistry 2002, 106(2), 379.@footnote 2@ Jungwirth, P.; Tobias, D. J. J. Phys. Chem. B 2002, 106, 6361.@footnote 3@ Finlayson-Pitts, B. J.; Hemminger, J. C. J. Phys. Chem. 2000, 104(49), 11463 .