The Surface Structure of Concentrated Aqueous salt Solutions

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.2431361· OSTI ID:930632

Sloutskin, E; Baumert, J; Ocko, B; Kuzmenko, I; Checco, A; Tamam, L; Ofer, E; Gog, T; Deutsch, M

The surface-normal electron density profile {rho}{sub s}(z) of concentrated aqueous salt solutions of RbBr, CsCl, LiBr, RbCl, and SrCl{sub 2} was determined by x-ray reflectivity (XR). For all but RbBr and SrCl{sub 2} {rho}{sub s}(z) increases monotonically with depth z from {rho}{sub s}(z)=0 in the vapor (z<0) to {rho}{sub s}(z) = {rho}{sub b} of the bulk (z>0) over a width of a few angstroms. The width is commensurate with the expected interface broadening by thermally excited capillary waves. Anomalous (resonant) XR of RbBr reveals a depletion at the surface of Br{sup -} ions to a depth of {approx}10 A. For SrCl{sub 2}, the observed {rho}{sub s}(z)>{rho}{sub b} may imply a similar surface depletion of Cl{sup -} ions to a depth of a few angstroms. However, as the deviations of the XRs of RbBr and SrCl{sub 2} from those of the other solutions are small, the evidence for a different ion composition in the surface and the bulk is not strongly conclusive. Overall, these results contrast earlier theoretical and simulational results and nonstructural measurements, where significant surface layering of alternate, oppositely charged, ions is concluded.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 930632
• Report Number(s): BNL--80985-2008-JA
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 5 Vol. 126; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
AQUEOUS SOLUTIONS
CESIUM CHLORIDES
ELECTRON DENSITY
LITHIUM BROMIDES
MORPHOLOGY
RUBIDIUM BROMIDES
RUBIDIUM CHLORIDES
STRONTIUM CHLORIDES
SURFACE PROPERTIES
national synchrotron light source