Theory of Elementary Processes

Calculation of the rate constants of various elementary gas reactions essentially consists of two independent parts dynamical and statistical. Such independent treatment is based on the fact that the duration of molecular collisions to 

10 13 g) jg typically much shorter than the average time between successive collisions s under normal conditions). Thus, we can choose a time interval 

The second task consists in the calculation of the macroscopic rate constants of various processes which can be measured directly. The theory uses here various types of kinetic equations for the evolution of population of molecular quantum states caused by many successive collisions. This permits to obtain distribution functions which frequently might be very different from equilibrium distribution. When the distribution is known it can be used to calculate the macroscopic rate. 

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E. E. Nikitin and L. Zulicke, Lecture Notes in Chemistry, Theory of Elementary Processes, Vol. 8, Springer-Verlag, Heidelberg, 1978. 

Pure chemical kinetics is concerned with the theory of elementary processes and reaction mechanisms. Several books deal with the general problems of chemical kinetics [1—6], whereas others are oriented more towards homogeneous chemical kinetics [7—13]. 

Nowadays, the basic framework of our understanding of elementary processes is the transition state or activated complex theory. Formulations of this theory may be found in refs. 1—13. Recent achievements have been the Rice—Ramsperger—Kassel—Marcus (RRKM) theory of unimol-ecular reactions (see, for example, ref. 14 and Chap. 4 of this volume) and the so-called thermochemical kinetics developed by Benson and co-workers [15] for estimating thermodynamic and kinetic parameters of gas phase reactions. Computers are used in the theory of elementary processes for quantum mechanical and statistical mechanical computations. However, this theme will not be discussed further here. 

The adiabatic approximation is a simplification widely used in the theory of elementary processes. 

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