Statistical quantum studies on insertion atom–diatom reactions

Abstract

The study of insertion atom–diatom reactions is usually complicated by the existence of deep potential wells between reactants and products. The large number of bound and resonance states to be properly described makes exact quantum mechanical calculations extremely demanding in terms of numerical effort. In this type of collision, the process proceeds via the formation of an intermediate complex of finite lifetime. The application of statistical quantum methods provides a valid alternative to investigate the dynamics of the reaction. In this work, studies performed with a statistical quantum method recently developed by Rackham et al. on a variety of different reactions are extensively reviewed. The overall dynamics of the processes selected to test this statistical model range from complex-forming mechanisms to a competition between insertion and direct abstraction reaction pathways. This review includes studies of X + H₂ reactions, where X is one of the following electronically excited non-metallic atoms: C(¹ D), N(² D), O(¹ D) or S(¹ D). An ion–diatom collision, the H system (with its isotope variants), is also investigated. Finally, results of the statistical study of the H + O₂ reaction are discussed. In all cases, comparison with both exact quantum mechanical calculations and experimental measurements shows that the method provides valid and rigorous information about the underlying dynamics of the reactions under study.