Electron Spectroscopy of Aqueous Solution Interfaces Reveals Surface Enhancement of Halides.

SUTAPA GHOSAL,; C. HEMMINGER, JOHN; SIMON MUN, BONGJIN; HENDRIK BLUHM,; GUIDO KETTELER,; FRANK OGLETREE, D.; FELIX GREGORIO REQUEJO; MIQUEL SALMERON,

SCIENCE

Año: 2005 vol. 307 p. 563 - 563

0036-8075

It has been suggested that enhanced anion concentrations at the liquid/vaporinterface of airborne saline droplets are important to aerosol reactions in theatmosphere. We report ionic concentrations in the surface of such solutions.Using x-ray photoelectron spectroscopy operating at near ambient pressure,we have measured the composition of the liquid/vapor interface fordeliquesced samples of potassium bromide and potassium iodide. In bothcases, the surface composition of the saturated solution is enhanced in thehalide anion compared with the bulk of the solution. The enhancement ofanion concentration is more dramatic for the larger, more polarizable iodideanion. By varying photoelectron kinetic energies, we have obtained depthprofiles of the liquid/vapor interface. Our results are in good qualitativeagreement with classical molecular dynamics simulations. Quantitativecomparison between the experiments and the simulations indicates that theexperimental results exhibit more interface enhancement than predictedtheoretically.