Discharge-ionization step

Step), and leave the reaction area into bulk solution (second mass transfer). The mass transfer step, as well as the electrochemical one, are always present in any electrochemical transformation. Importantly, the electrochemical step is always accompanied by transfer of a charged particle through the interface. That is why this step is called the transfer step or the discharge-ionization step. Other complications are also possible. They are related to the formation of a new phase on the electrode (surface diffusion of adatoms, recombination of adatoms, formation of crystals or gas bubbles, etc.). The transfer step may be accompanied by different chemical reactions, both in bulk and on the electrode surface. A set of all the possible transformations is called the electrode process. Electrochemical kinetics works with the general description of electrode processes over time. While related to chemical kinetics, electrochemical kinetics has several important features. They are specific to the certain processes, in particular - the discharge-ionization step. Determination of a possible step order and the slowest (rate-determining) step is crucial for the description of the specific electrode process. 

Figure 5.1 shows the resulting relationship between the rate of the slow discharge-ionization step and overpotential calculated using (5.7). 

Fig. 5.1 Polarization curves for slow discharge-ionization step...

The theory of linear-sweep voltammetry (LSV) applied to heterogeneous redox reactions accompanied by the nondissociative adsorption of the reactant or the product is developed. The basic criterial relationships of LSV in this case are invariant with respect to the type of adsorption isotherm and the number of adsorption sites occupied by one species. The degree of irreversibility of the discharge-ionization step can be evaluated from the effect of the potential scan rate on the peak potential. The nature of the adsorbate can be deduced from the effect of the reactant concentrations on the peak current. 

Here, C, C2, and C3 are constants Cj is nonzero if the discharge-ionization step is kinetically irreversible and is equal to zero if this step is quasi-equilibrium. 

E(t)-c xrve is 0m = 0.5 if the discharge-ionization step is quasi-equilib-rium. Its value ean be determined by numerically solving the relevant transcendent equation provided that the adsorption isotherm is known. 

One can see that a shift in potential from its equilibrium value leads to different changes in the anode and cathode process rates. The dotted line represents partial polarization characteristics for the discharge and ionization steps. The resulting reaction rate depends on the overpotential exponentially. 

In the discharge of organic molecules, the ionization is not an accurate picture of the step that creates the luminous gas phase. First of all, the ionization energy... 

If one applies the same principle for Ar discharge to the glow discharge of organic molecules, the first step of ionization could be written as... 

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