Jump to main content
Jump to site search

Issue 32, 2008
Previous Article Next Article

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

Author affiliations

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.

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

Back to tab navigation

Publication details

The article was received on 25 Apr 2008, accepted on 24 Jun 2008 and first published on 16 Jul 2008


Article type: Paper
DOI: 10.1039/B807041E
Citation: Phys. Chem. Chem. Phys., 2008,10, 4778-4784
  •   Request permissions

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

    M. A. Brown, R. D’Auria, I.-F. W. Kuo, M. J. Krisch, D. E. Starr, H. Bluhm, D. J. Tobias and J. C. Hemminger, Phys. Chem. Chem. Phys., 2008, 10, 4778
    DOI: 10.1039/B807041E

Search articles by author

Spotlight

Advertisements