title: Solvation structures of protons and hydroxide ions in water.
abstract: X-ray Raman spectroscopy (XRS) combined with small-angle x-ray scattering (SAXS) were used to study aqueous solutions of HCl and NaOH. Hydrated structures of H(+) and OH(-) are not simple mirror images of each other. While both ions have been shown to strengthen local hydrogen bonds in the hydration shell as indicated by XRS, SAXS suggests that H(+) and OH(-) have qualitatively different long-range effects. The SAXS structure factor of HCl (aq) closely resembles that of pure water, while NaOH (aq) behaves similar to NaF (aq). We propose that protons only locally enhance hydrogen bonds while hydroxide ions induce tetrahedrality in the overall hydrogen bond network of water.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, California 94305, USA.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.forename: Congcong
authors.initials: C
authors.lastname: Huang
authors.forename: Iradwikanari
authors.initials: I
authors.lastname: Waluyo
authors.forename: Dennis
authors.initials: D
authors.lastname: Nordlund
authors.forename: Tsu-Chien
authors.initials: TC
authors.lastname: Weng
authors.forename: Dimosthenis
authors.initials: D
authors.lastname: Sokaras
authors.forename: Thomas
authors.initials: T
authors.lastname: Weiss
authors.forename: Uwe
authors.initials: U
authors.lastname: Bergmann
authors.forename: Lars G M
authors.initials: LG
authors.lastname: Pettersson
authors.forename: Anders
authors.initials: A
authors.lastname: Nilsson