Calculation of the microwave and far-infrared spectra of aqueous electrolyte solutions from a molecular model. On the ionic-conductivity dispersion σ(ω)
✍ Scribed by Vladimir I. Gaiduk; Boris M. Tseitlin; Derrick S.F. Crothers
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 963 KB
- Volume
- 89
- Category
- Article
- ISSN
- 0167-7322
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✦ Synopsis
A simple model of dielectric response due to the three-dimensional motion of ions inside a spherical ideally reflecting sheath is suggested. The present model termed the sphere-confined ionic (SCI) model is combined with the so called hybrid model, previously used to describe dipolar orientational relaxation [see Dielectric Relaxation and Dynamics of Polar Molecules by V, I. Gaiduk (World Scientific, Singapore, 1999)]. The wideband (up to 1000 cm -I) complex permittivity g(0)) and absorption ~(0)) spectra of NaCl-water and KCl-water diluted solutions are calculated as the sum of the contributions due to cations and anions and to reorientation of polm H20 molecules. A modification of this model is also suggested, in which the walls may also vibrate.
The parametrisation of the ionic model is made taking account of the experimental value (3"s of the static conductivity; the ionic contributions 0 "+ due to anions and cations arc calculated, as well as ionic self-diffusion coefficients and mobilities. '['he positive (for NaCI) and negative (for KC1) hydration are described in terms of respectively increasing and decreasing X(CM) concentration dependencies of the lifetimes fitted for water molecules.
The frequency dependence of the electric conductivity is estimated for a relatively low electrolyte concentration. If the frequency 0) is much less than the ionic plasma frequency 0)p, then the real part (3' of the complex ionic conductivity is close to its static value (Ys, while the imaginary part (Y" is close to zero. In the high-flequency region (at millimetre/submillimetre wavelengths) the