NDLI: Ion spatial distributions at the liquid–vapor interface of aqueous potassium fluoride solutions

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Brown, Matthew A. D'Auria, Raffaella Kuo, I-F William Krisch, Maria J. Starr, David E. Bluhm, Hendrik Tobias, Douglas J. Hemminger, John C.
Description	Country affiliation: United States Author Affiliation: Brown MA ( Department of Chemistry and Air UCI, University of California-Irvine, Irvine, CA 92697, USA.)
Abstract	X-Ray photoemission spectroscopy operating under ambient pressure conditions is used to probe ion distributions throughout the interfacial region of a free-flowing aqueous liquid micro-jet of 6 M potassium fluoride . Varying the energy of the ejected photoelectrons by carrying out experiments as a function of X-ray wavelength measures the composition of the aqueous–vapor interfacial region at various depths. The $F^{−}$ to $K^{+}$ atomic ratio is equal to unity throughout the interfacial region to a depth of 2 nm. The experimental ion profiles are compared with the results of a classical molecular dynamics simulation of a 6 M aqueous KF solution employing polarizable potentials. The experimental results are in qualitative agreement with the simulations when integrated over an exponentially decaying probe depth characteristic of an APPES experiment. First principles molecular dynamics simulations have been used to calculate the potential of mean force for moving a fluoride anion across the air–water interface. The results show that the fluoride anion is repelled from the interface, consistent with the depletion of $F^{−}$ at the interface revealed by the APPES experiment and polarizable force field-based molecular dynamics simulation. Together, the APPES and MD simulation data provide a detailed description of the aqueous–vapor interface of alkali fluoride systems. This work offers the first direct observation of the ion distribution at an aqueous potassium fluoride solution interface. The current experimental results are compared to those previously obtained for saturated solutions of KBr and KI to underscore the strong difference in surface propensity between soft/large and hard/small halide ions in aqueous solution.
File Format	HTM / HTML
ISSN	14639076
Issue Number	32
Journal	Physical Chemistry Chemical Physics
Volume Number	10
e-ISSN	14639084
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2008-08-28
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Discipline Physics Discipline Biophysics Discipline Chemistry
Alternative Title	Ion spatial distributions at the liquid-vapor interface of aqueous potassium fluoride solutions
Content Type	Text
Resource Type	Article
Subject	Physics and Astronomy Physical and Theoretical Chemistry

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