4. Structure of Ionic Hydration Shells 1351 4.1. Results from Diffraction Experiments 1351 4.1.1. X-ray Diffraction 1351 4.1.2. Neutron Diffraction 1351 4.2. Results from Computer Simulations 1352 4.3. Results from Spectroscopic Measurements 1354 4.3.1. Vibrational Spectroscopic Measurements 1354 4.3.2. EXAFS Spectroscopy 1354 4.3.3. NMR Relaxation Studies 1355 4.3.4. Dielectric Relaxation Studies 1355 4.4. Summary of the Structure of Ionic Hydration Shells 1355

Effect of ions on the structure of water: structure making and breaking.

Extensive terahertz laser vibration-rotation-tunneling spectra and mid-IR laser spectra have been compiled for several isotopomers of small (dimer through hexamer) water clusters These data, in conjunction with new theoretical advances, quantify the structures, force fields, dipole moments, and hydrogen bond rearrangement dynamics in these clusters This new information permits us to systematically untangle the intricacies associated with cooperative hydrogen bonding and promises to lead to a more complete molecular description of the liquid and solid phases of water, including an accurate universal force field

/pdf/water-clusters-untangling-the-mysteries-of-the-liquid-one-1b5uj00qz0.pdf

Water clusters: Untangling the mysteries of the liquid, one molecule at a time

All the currently available experimental permittivity data for pure water are used to derive an interpolation function that precisely represents e(ν,t,) at standard atmospheric pressure, for frequencies and temperatures in the ranges 0⩽ν⩽25THz and 0⩽t⩽100°C. The permittivity data is represented in terms of relaxations and resonances processes. There are three relaxations in the microwave region and two resonances in the far infrared. The temperature dependence of the relaxation and resonance parameters are determined. For example, at 25°C the three relaxation frequencies are 18.56GHz, 167.83GHz, 1.944THz and the two resonance frequencies are 4.03 and 14.48THz.

Permittivity of pure water, at standard atmospheric pressure, over the frequency range 0-25 THz and the temperature range 0-100 °C

The complex dielectric permittivity of aqueous sodium chloride solutions has been determined in the frequency range 0.2 ≤ v(GHz) ≤ 20 with a commercial dielectric measurement system based on a vector network analyzer. NaCl solutions 0.1 ≤ m (mol kg-1) ≤ 5 (mass fraction 0.005 ≤ w ≤ 0.23) were investigated at 5, 20, 25, and 35°C. An improved calibration procedure of the dielectric measurement system for conducting samples was developed. The complex permittivity spectra have been represented by a Cole-Cole relaxation time distribution. Where possible, the obtained fitting parameters, static permittivity ∈ and relaxation time τ, and distribution parameter a, are compared with literature data to assess the performance of the instrument, which was found to be comparable to that of time domain and waveguide systems. Effective solvation numbers were deduced from the effect of NaCl concentration on ∈. The data suggest that in addition to the irrotational bonding of water molecules by Na+ ions, kinetic depolarization under slip boundary conditions determines the solution permittivity. A three-state model is proposed to describe the concentration dependence of τ. © Copyright 1999 by the American Chemical Society.

Dielectric relaxation of aqueous NaCl solutions

Neat liquid phosphoric acid (H(3)PO(4)) has the highest intrinsic proton conductivity of any known substance and is a useful model for understanding proton transport in other phosphate-based systems in biology and clean energy technologies. Here, we present an ab initio molecular dynamics study that reveals, for the first time, the microscopic mechanism of this high proton conductivity. Anomalously fast proton transport in hydrogen-bonded systems involves a structural diffusion mechanism in which intramolecular proton transfer is driven by specific hydrogen bond rearrangements in the surrounding environment. Aqueous media transport excess charge defects through local hydrogen bond rearrangements that drive individual proton transfer reactions. In contrast, strong, polarizable hydrogen bonds in phosphoric acid produce coupled proton motion and a pronounced protic dielectric response of the medium, leading to the formation of extended, polarized hydrogen-bonded chains. The interplay between these chains and a frustrated hydrogen-bond network gives rise to the high proton conductivity.

J. Stauber

Papers

The dielectric relaxation of water between 0°C and 35°C

Dielectric relaxation spectroscopy of electrolyte solutions. recent developments and prospects