title: A different view of structure-making and structure-breaking in alkali halide aqueous solutions through x-ray absorption spectroscopy.
abstract: X-ray absorption spectroscopy measured in transmission mode was used to study the effect of alkali and halide ions on the hydrogen-bonding (H-bonding) network of water. Cl(-) and Br(-) are shown to have insignificant effect on the structure of water while I(-) locally weakens the H-bonding, as indicated by a sharp increase of the main-edge feature in the x-ray absorption spectra. All alkali cations act as structure-breakers in water, weakening the H-bonding network. The spectral changes are similar to spectra of high density ices where the 2nd shell has collapsed due to a break-down of the tetrahedral structures, although here, around the ions, the breakdown of the local tetrahedrality is rather due to non-directional H-bonding to the larger anions. In addition, results from temperature-dependent x-ray Raman scattering measurements of NaCl solution confirm the H-bond breaking effect of Na(+) and the effect on the liquid as similar to an increase in temperature.
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309, USA.
authors.forename: Iradwikanari
authors.initials: I
authors.lastname: Waluyo
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309, USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Nordlund
authors.affiliation: Linac Coherent Light Source, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309, USA.
authors.forename: Uwe
authors.initials: U
authors.lastname: Bergmann
authors.affiliation: Department of Physics, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schlesinger
authors.affiliation: Department of Physics, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Lars G M
authors.initials: LG
authors.lastname: Pettersson
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309, USA.
authors.forename: Anders
authors.initials: A
authors.lastname: Nilsson
mesh_terms: D000468:Alkalies / Q000737:chemistry; D006860:Hydrogen Bonding; D007477:Ions; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014867:Water / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000468:Alkalies; D007477:Ions; D012996:Solutions; D014867:Water; D012965:Sodium Chloride