Unimolecular reactions QRRK theory

Rice, Ramsperger, and Kassel [206,333,334] developed further refinements in the theory of unimolecular reactions in what is known as RRK theory. Kassel extended the model to account for quantum effects [207] this treatment is known as QRRK theory. 

The reaction scheme in the QRRK theory for unimolecular decomposition can be written... 

The modem theory theory of unimolecular reactions was established by Marcus, who built upon QRRK theory [260,261,431]. This work is known as the RRKM theory. We will... 

This section treats the theory of chemical activation reactions more rigorously, at the same level of approximation as in the discussion of unimolecular reactions in Section 10.4.4. That is, the QRRK theory of chemical activation reactions is developed here. This theory for bimolecular reactions was set out by Dean and coworkers [93,428],... 

Multifrequency Quantum Rice-Ramsperger-Kassel (QRRK) is a method used to predict temperature and pressure-dependent rate coefficients for complex bimolecular chemical activation and unimolecular dissociation reactions. Both the forward and reverse paths are included for adducts, but product formation is not reversible in the analysis. A three-frequency version of QRRK theory is developed coupled with a Master Equation model to account for collisional deactivation (fall-off). The QRRK/Master Equation analysis is described thoroughly by Chang et al. [62, 63]. 

For reactions that are unimolecular in one or both directions, the reaction rate is expected to be pressure dependent, as discussed in detail in an earlier chapter of this text. In the high-pressure limit, conventional transition state theory as described in the previous section can be applied to estimate the rate constant. The only change in equation (20) is that only a single reactant partition function appears in the denominator. The pressure dependence can then be described at various levels of sophistication, from QRRK theory to RRKM theory, to full master equation treatments using microcanonical rate constants from RRKM theory, as described in the chapter by Carstensen and Dean. Because these approaches have been described in detail there, they are not treated in the present chapter. 

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