A more precise definition for the tunneling distance

For sufficiently large observation times the stepwise approximation of the function 0(R,t) in the form used in Sect. 2.1 is justified owing to the sharp dependence of the tunneling probability on the distance. As an example, in 

It can be seen that the function obtained as a result of the stepwise approximation differs to a comparatively small extent from the precise function. Nevertheless, in some cases even this small difference can result in considerable errors in describing the process kinetics, especially at short observation times. 

A general theoretical analysis of the necessary and sufficient conditions for the applicability of the stepwise approximation for describing the kinetics of electron tunneling reactions has been made in ref. 13. As shown in this reference, the stepwise approximation can also be used for describing the kinetics of electron tunneling reactions at such dependences lF(i ), which are more complicated than a simple exponent. For determining the distance of tunneling Rt [i.e. the radius of the stepwise approximation of the function 0(R,t)] it appears expedient (see ref. 13) to use the expression 

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