State cybotactic

The physical sense of molecular structure is not fully tmderstood. But studies of water solutions by various methods indicate that the area of its distribution oversteps botmdaries of the hydrates. In this connection in the molecular structure arotmd each ion are identified two spheres of the molecular structure inner, or internal hydration shell (Figure 1.2), and outer, or external hydration shell (Figure 1.2). Inner or primary hydration shell is positioned within the hydrate and is caused by direct orientation interaction of H O with ions. Outer hydration shell is caused by the competitive efiect on H O from the ion, on the one hand, and from interdipole hydrogen bonds on the other. Such disrupted H O dipole structure is sometimes called cybotactic state. 

A suitable probe for the general solvent effect must therefore be a polar compound. Around its dipole moment, the solvent molecules will arrange themselves as effectively as possible -in thermal equilibrium- and the interaction between the probe dipole and the solvent molecules that form the cybotactic region must be strongly altered by electronic excitation, which will result in an appropriate shift in charge the charge will then create a new dipole moment enclosed by the same cybotactic cavity as in the initial state of the transition. 

The concept of the molecules local ordering in a liquid (in contrast to no gas structure ) appeared in the 1920-ies, when Stuart introduced the notion of cybotactic area [79]. The ideology of the particles aggregation in the liquid systems has had a long history (see papers [73,77,80-82]), the attempts to express this idea quantitatively within the colloidal approximation go back to the works of Smolukhovsky [83] and Osvald [84]. The further development of the liquid state theory is connected with the works of Ya. Frenkel, J. Bernal et al. (e.g. see [73,80-82]). 

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