Ionic vibration

Conway has suggested a method that seems to give results in agreement with those of a second entirely different method, the ionic vibration method (see later discussion). Conway found that plotting the partial molar volume of a series of electrolytes involving large cations (e.g., a tetraalkylammonium series) and a constant smaller... 

In the next section it will be shown how these total solvation numbers for salts can be turned into individual solvation numbers for the ions in the salt by the use of information on what are called ionic vibration potentials, an electrical potential... 

Ionic Vibration Potentials Their Use in Obtaining the Difference of the Solvation Numbers of Two Ions in a Salt... 

In 1933 Peter Debye formulated a sophisticated theory about all this. He assumed, as is also intuitively obvious, that the supersonic emf, that is, the ionic vibration potential produced by the ultrasonic beam, would be proportional to the difference of the masses of the moving ions. Debye s expression can be reduced to... 

Obtaining the individual properties of ions with solvation numbers from measurements of ionic vibration potentials and partial molar volumes is not necessary in the study of gas phase solvation (Section 2.13), where the individual heats of certain hydrated entities can be obtained from mass spectroscopy measurements. One injects a spray of the solution under study into a mass spectrometer and investigates the time of flight, thus leading to a determination of the total mass of individual ions and adherent water molecules. 

The experiments performed by several research groups showed good agreement of theoretical predictions with the experimental data. This is rather encouraging and a little surprising result, keeping in mind that the experiments with simple electrolytes (where a similar effect called ionic vibration potential exists ) produced data that are often not well explained by the corresponding theory. The CVP technique can be applied to concentrated dispersions. 

The following sections present a treatment of the channel ion problem in three dimensions. The basis functions, although limited, now allow for the mixing of ionic vibrational modes along die channel axis in the axial and transverse directions. Moreover, it is possible to consider in detail the nature of the mobile ion/channel wall source phonon interaction, as will be discussed later. 

When there is more than one ion in the channel, the ion-ion interaction changes the nature of the problem. If the concentration is sufficiently great, the ions are closer together and this closeness greatly increases the values for the vibrational frequencies polarized along the channel axis. Thus, frequency shifts for axially polarized ionic vibrations may be a measure of the density of ionic concentration in the channel. 

Finally, a cautionary note must be added. Wall distortion has not been considered. It is possible that the interaction between wall-dressed ions is much different than the bare interaction. In view of the blue-shifting dressing with wall phonons may yield, the ultimate interpretation of channel ionic vibrations in multiply occupied systems may be a challenge. 

As the reactants become more complex, the analysis becomes more difficult. However, if both reactants are diatomic, the analysis is almost as straightforward. The low temperature data contain only rotational excitation, however, both reactants are rotationally excited. The rotational temperature of the ionic reactant in a drift tube is calculated from the CM energy with the buffer mass substituted for the reactant mass by assuming KEb f = 3/2kTi.ot- The rotational distribution is expected to be close to Boltzmann. Vibrational excitation also occurs in both reactants. The ionic vibrational temperature is the same as that for rotations for a steady state situation and this assumption is used in all the work described here. The contributions from ionic and neutral vibrations can only be separated if independent information exists regarding how vibrational excitation of one of the reactants affects the reactivity. In practice, if any such information is available, it is likely to be the vibrational dependence of the primary reactant ion. 

In 1933 Debye published a theoretical study in which he predicted the origination of an electric field, the so-called ionic vibration potential (IVP), upon the passage of ultrasonic waves through electrolyte solutions [34]. Debye outlined that ultrasonic waves should cause the separation of charges due to the differences in the effective masses and friction coefficients of the solvated anions and cations, and suggested that such an effect might serve as a means... 

The effect of ionic vibrational energy was first examined for the reaction... 

The time constant of this process is about 10 s and therefore occurs in the UV region of the electromagnetic spectrum. Ionic vibrations have a time constant which usually occurs in the infrared and are also therefore instantaneous as far as electrochemical experiments are concerned. 

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