Ionic Atmosphere


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Ionic Atmosphere

 

an increased concentration of ions of opposite charge in the volume surrounding a given ion in solution; it forms because of the action of the electric field generated by the ion. The total charge of the ionic atmosphere is equal in magnitude to the charge of the ion but is of opposite sign.

The concept of ionic atmosphere simplifies calculation of interactions between ions in solution using statistical methods (by examining the continuous field of the ionic atmosphere of the ion rather than the electric fields generated by each ion surrounding the central ion). Each ion, including any ion forming a part of the ionic atmosphere of a given ion, may be regarded as a central ion having its own atmosphere.

V. A. KIREEV

References in periodicals archive ?
It was generally assumed that, when the concentration CP of a polyelectrolyte is sufficiently low, screen effect due to free counterions of ionic atmosphere is relatively weak so that the intrarepulsion between charged monomers inside each flexible chain of structural length [L.sub.s] prevents the collapse of the polyion and consequently the stretched configuration becomes the most probable at high dilution.
The different contributions have been expressed in terms of the degree of dissociation of counterions a, the geometric parameters of the ellipsoidal polyion R and L, the effective radius of the counterions [R.sub.k], the charge numbers of the polyion and the counterions respectively, [Z.sub.s], [Z.sub.k], and also in terms of the minor axis of the ellipsoidal ionic atmosphere surrounding the polyion, d, (see Figure 1) which depends on the concentration [alpha][C[degrees].sub.k] of free counterions and therefore on the Debye-MSA [8-11] screen parameters [[GAMMA].sub.MSA] and [[chi].sub.d] (in [[Angstrom].sup.-1]):
F = [eN.sub.A] is the Faraday, <R> and <d> are, respectively, the mean radius of the polyion and of its ionic atmosphere defined as follows:
The ionic friction due to the perturbation of the ionic atmosphere during its relaxation is expressed in terms of the coefficient [[beta].sub.P.sup.ir] as follows:
E comes out from the solution of Poisson equation, which basically depends on ionic atmosphere of the point of calculation.
Diffusivity normally changes with porosity of polymeric membranes, ionic sizes and ionic atmosphere of the membrane.