Rice-Ramsperger-Kassel-Marcus RRKM method

Another advantage of the quantum calculations is that they provide a rigorous test of approximate methods for calculating dissociation rates, namely classical trajectories and statistical models. Two commonly used statistical theories are the Rice-Ramsperger-Kassel-Marcus (RRKM) theory and the statistical adiabatic channel model (SACM). The first one is thoroughly discussed in Chapter 2, while the second one is briefly reviewed in the Introduction. Moreover, the quantum mechanical approach is indispensable in analyzing the reaction mechanisms. A resonance state is characterized not only by its position, width and the distribution of product states, but also by an individual wave function. Analysis of the nodal structure of resonance wave functions gives direct access to the mechanisms of state- and mode-selectivity. 

Single-pulse shock tube studies of the thermal dehydrochlorination reactions of chlorocyclopentane and chlorocyclohexane at temperatures of 843-1021 K and pressures of 1.4-2.4 bar have been carried out using the comparative rate technique. Absolute rate constants provided a self-consistent temperature scale of use in comparison with chemical systems studied with different temperature standards. Quantum chemical methods have been used to compute the structure and energies of reactants, products, and transition states. The computations were used, in conjunction with experimentally determined rate constants, to develop Rice-Ramsperger-Kassel-Marcus (RRKM)/ Master Equation models and thereby allow extrapolation of the experimental data over an extended range of temperatures. 

A discussion of recent published results on the cyclobutane reaction illustrates the kind of excited molecule dynamical information available from recoil techniques. The primary assumption in the approach reported is that the RRKM (Rice-Ramsperger-Kassel-Marcus) method for describing statistical energy redistribution and calculating decomposition rate constants is valid. TTius, deviations from expected RRKM behavior... 

The methods for the calculation of k(e, J) are related to the RRKM theory (abbreviation of the first letters of surnames of scientists who developed the theory Rice, Ramsperger, Kassel, Marcus). 

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