Study of the H+O2 reaction by means of quantum mechanical and statistical approaches:: The dynamics on two different potential energy surfaces

The possible existence of a complex-forming pathway for the H+O-2 reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana , J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6 eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O-2(upsilon=0,j=1)-> OH(upsilon'=1,j')+O process reasonably well. (c) 2008 American Institute of Physics.