Stationary-state hypothesis significance

This procedure constitutes an application of the steady-state approximation [also called the quasi-steady-state approximation, the Bodenstein approximation, or the stationary-state hypothesis]. It is a powerful method for the simplification of complicated rate equations, but because it is an approximation, it is not always valid. Sometimes the inapplicability of the steady-state approximation is easily detected for example, Eq. (3-143) predicts simple first-order behavior, and significant deviation from this behavior is evidence that the approximation cannot be applied. In more complex systems the validity of the steady-state approximation may be difficult to assess. Because it is an approximation in wide use, much critical attention has been directed to the steady-state hypothesis. 

When considering regularities of these processes, two main alternatives are to be distinguished, depending on which of the electric parameters i or E) are controlled during the experiment. However, under steady-state conditions, these differences disappear. Moreover, according to the hypothesis put forward in Ref. [1], selection of the controlled electric parameter has no significance in the case of quasi-stationary states, which, for example, are reached in the impedance spectroscopy or in the electrolysis of periodic impulses of small amplitude. 

Not only these term differences, but also the terms themselves, have a physical significance. Thanks to our hypothesis regarding the potential energy, which we have supposed to vanish at infinity, the magnitude W of the energy constant denotes the work which is necessary to remove an electron from its stationary orbit to infinity and to bring it to rest there (relatively to the nucleus). If the stationary orbit of the electron is that of the normal state, then this work is the work of ionisation. 

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