title: Existence of oriented ion-hydroxide clusters in concentrated aqueous NaCl solution at pH 13.
abstract: We probe the local electronic structure at solvated Na+ ions in 1 M aqueous NaCl solutions as a function of pH. A dramatic change in the Na+ white line intensity in X-ray absorption is observed for high pH values, reflecting a changing local electronic structure at the Na+ ions when OH- is present. Given the relative abundance of sodium and hydroxide ions, we conclude that one OH- affects at least 2.4+/-0.6 Na+ ions in an electronically noticeable way at pH 13. From the experimental data we infer that spatially extended clusters or networks incorporating Na+ and OH- can exist in the electrolyte solution. The experimental data are complemented by molecular dynamics simulations, which indicate the presence of structured clusters incorporating Na+, OH-, and solvent molecules.
authors.affiliation: BESSY m.b.H., Albert-Einstein Str. 15,12489 Berlin, Germany.
authors.forename: Emad F
authors.initials: EF
authors.lastname: Aziz
authors.forename: Stefan
authors.initials: S
authors.lastname: Eisebitt
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eberhardt
authors.forename: Lukasz
authors.initials: L
authors.lastname: Cwiklik
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
mesh_terms: D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties
chemical_list: D006878:Hydroxides; D012996:Solutions; D012965:Sodium Chloride; C031356:hydroxide ion; D010100:Oxygen