Simplification of the transition state concept in reactive island theory: Application to the HCNrlarr2;CNH isomerization

摘要

The reactive island (RI) theory of chemical reaction rates is modified so that a precise knowledge of the transition state is not required. This revised form of the theory is applied to a realistic two (J=0) and three degree of freedom model (Jne;0) of the isomerization HCNrlarr2;CNH. The detailed reaction dynamics is examined and understood in terms of the cylindrical manifolds embedded in the molecular phase space. Of special interest we find a Thyphen;shaped conformer in addition to the HCN and CNH moieties atJ=0. Rates of unimolecular decay are examined by numerical simulation and theory. Good agreement is found between theory and simulation except for a case where a substantial amount of phase space is consumed by regular motion. In all cases studied, the theory is a significant improvement over the Ricendash;Ramspergerndash;Kasselndash;Marcus (RRKM) theory, which is up to three orders of magnitude too large. thinsp;