Cross sections and rate constants for triatomic and tetraatomic reactions: Three-dimensional quantum mechanical calculations

We are presenting a short review on our recent quantum mechanical calculations of reactive cross sections and rate constants. Seven different cases are considered: The two triatom systems, namely F + H₂ and F + D₂, were treated twice employing two different potential energy surfaces. The calculations were carried out within the coupled states approximation. Two atom-triatom reactions were considered: the O + O₃ reaction, for which the calculations were done employing the quasi-breathing-sphere approximation, and the H + H₂O reaction for which the calculations were done employing the (cruder) infinite-order-sudden-approximation. One diatom-diatom system, namely H₂ + OH, was considered. For this system the calculations were carried out twice: once employing the infinite-order-sudden-approximation and once employing a mixed version of the coupled states approximation (with regard to the "reactive angle") and the infinite order sudden approximation (with regard to the other two angles). All calculations were carried out in the reagents' arrangement channel employing negative imaginary arrangement-decoupling potentials. In general very encouraging agreement with experiment was obtained.