Anion polarization energy

Again we digress to discuss soft and hard (11). It has been said that polarizability measures softness and that the permanent charge-cloud distortion is responsible for (b)-class behaviour. Unfortunately polarization energies of this kind work in two ways — they generate (i) (b)-class behaviour due to anion polarizability but (ii) (a)-class behaviour due to the cation polarizability. Thus if softness and polarizability are related they are not necessarily related to (b)-class behaviour. Moreover on the basis of polarizability of this kind there can be no preferential soft-soft or hard-hard interaction. 

The value of one half of the anion-cation energy-difference is the polar energy ... 

In photodetachment studies we need not be concerned with the coulombic interaction that dominates the neutralization channel in MPI at times <10 ° s, but since the threshold for ionization of an anion is higher in the liquid than in the gas phase, we obtain once again information on the polarization energy of the ion in the liquid prior to photo-detachment. The laser photodetachment mechanism has been used with inorganic ions, such as Fe(CN)g or organic ions such as phenolate, supported in a wide range of aqueous or organic liquids. 

The decrease in ionization energy in solution is due to the effect of I1 which is always greater than I Vq I. If the same solute is measured in different hydrocarbons, approximately the same polarization energy should result, since is approximately 2 for most of the hydrocarbons. In Table 5, the polarization energies of the positive anthracene ion in three different solvents are given. A value of -1.06 eV is obtained for all three solvents which is an indication that the anion radius is constant, since Er is approximately the same for the three liquids. 

In these models the application of pressure alters the balance between increasing the nearest-neighbouring coordination number (increasing the packing fraction) and a reduction in the polarization energy (as a result of the anions changing coordination number from two to three). 

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