Rice-Rampsberger-Kassel-Marcus RRKM Treatment

The activation energy predicted by the formulation of Hinshelwood differs from that predicted by simple collision theory 

In spite of the progress that the treatment of Hinshelwood has brought to the field, some difficulties remain. One that persisted was the reciprocal dependence of l/k versus the reciprocal of concentration, which as we have seen is not found at high pressures. However, there are other problems, such as the fact that the number of degrees of freedom required to reproduce experimental data is one-half of the total number of vibrational modes. Also, according to eq. (8.23), one would also expect a strong temperature dependence of the preexponential factor, especially for large values of s. There is no experimental evidence for this prediction. 

3 RICE-RAMPSBERGER-KASSEL-MARCUS (RRKM) TREATMENT 

The highly energised molecule A has a metastable nature due to reasons associated with the slowness of the internal energy flow or, with the insight provided by the RRKM theory, to an entropy barrier arising from the improbability of concentrating vibrational 

In the limit of high pressures, the theory RRK leads to the limiting high-pressure first-order rate constant of the conventional transition-state theory 

---

Rice-Rampsberger-Kassel-Marcus (RRKM) Treatment... 

---