IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Biomaterials Monday Sessions
       Session BI+SS-MoA

Paper BI+SS-MoA9
X-Ray Absorption Spectroscopy of Liquid and Gaseous Water

Monday, October 29, 2001, 4:40 pm, Room 102

Session: Role of Water in Biological Systems
Presenter: K.R. Wilson, University of California-Berkeley
Authors: K.R. Wilson, University of California-Berkeley
R.J. Saykally, University of California-Berkeley
J.G. Tobin, Lawrence Livermore National Laboratory
Correspondent: Click to Email
X-ray absorption fine structure (XAFS) measurements have been performed upon liquid@footnote 1@ and gaseous@footnote 2@ H2O. Using the O1s level as the means of achieving elemental specificity, both near edge (NEXAFS) and extended X-ray absorption fine structure (EXAFS) have been measured. Liquid water samples were achieved in the vacuum system via the utilization of a liquid jet system modelled after that of Faubel et al.@footnote 3@ In the investigation of liquid water, both ions and electrons were used as a means of detection. This permitted the separation of liquid surface effects (ions) from bulk-like behavior (electrons). In the NEXAFS regime, the surface sensitive spectrum resembled that of gaseous water while the bulk-sensitive spectrum exhibited broadening and a blue shift. Similarly, differences were observed in the EXAFS results derived from each detection method, i.e. surface vs. bulk. The measurement of the EXAFS in liquid water encouraged us to go back and perform similar measurements upon gaseous water. A single oscillation was observed from gaseous water consistent with the location of the covalently bonded hydrogen in H2O. The experimental phase and amplitude of the oscillation are in excellent agreement with curved wave multiple scattering calculations for isolated water molecules, performed by Ankudinov and Rehr.@footnote 2@ With this determination of the O-H scattering phase shift , the covalent hydrogen bond distance (0.95 + 0.03 Ã…) in liquid water has been quantified, thus demonstrating that hydrogen EXAFS can become a valuable complement to existing structural methods in chemistry and biology. @FootnoteText@ @footnote 1@K. R. Wilson, et al, J. Chem. Phys. B, May 2001. @footnote 2@K. R. Wilson, et al, Phys. Rev. Lett. 85,4289 (2000). @footnote 3@M. Faubel et al, J.Chem. Phys. 106, 9013 (1997).