title: Nearest-neighbor oxygen distances in liquid water and ice observed by x-ray Raman based extended x-ray absorption fine structure.
abstract: We report the nearest-neighbor oxygen-oxygen radial distribution function (NN O-O RDF) of room temperature liquid water and polycrystalline ice Ih (-16.8 degrees C) obtained by x-ray Raman based extended x-ray absorption fine structure (EXAFS) spectroscopy. The spectra of the two systems were taken under identical experimental conditions using the same procedures to obtain the NN O-O RDFs. This protocol ensured a measurement of the relative distance distribution with very small systematic errors. The NN O-O RDF of water is found to be more asymmetric (tail extending to longer distances) with longer average distance (2.81 A for water and 2.76 A for ice) but a slightly shorter peak position (2.70 A for water and 2.71 A for ice). The refinement also showed a small but significant contribution from the linear O-H-O multiple scattering signal. The high sensitivity to short range distances of the EXAFS probe will set further restrictions to the range of possible models of liquid water.
authors.affiliation: Stanford Synchrotron Radiation Laboratory, PO Box 20450 Stanford, California 94309, USA. bergmann@slac.stanford.edu
authors.forename: Uwe
authors.initials: U
authors.lastname: Bergmann
authors.forename: Andrea
authors.initials: A
authors.lastname: Di Cicco
authors.forename: Philippe
authors.initials: P
authors.lastname: Wernet
authors.forename: Emiliano
authors.initials: E
authors.lastname: Principi
authors.forename: Pieter
authors.initials: P
authors.lastname: Glatzel
authors.forename: Anders
authors.initials: A
authors.lastname: Nilsson
mesh_terms: D002627:Chemistry, Physical / Q000379:methods; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D007053:Ice; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry; D044367:Phase Transition; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D007053:Ice; D014867:Water; D006859:Hydrogen; D010100:Oxygen