Time-dependent quantum mechanical calculations on H+O-2 for total angular momentum J > 0: Comparing different dynamical approximations

The H + O-2 --> OH + O reaction has been studied with a time-dependent wave packet method for total angular momentum J > 0 using three different appro ximations: the J-shifting approximation, the helicity conserving approximat ion, and the truncated basis approximation. Both reaction probabilities and reaction cross sections are calculated and compared to recent rigorous clo se coupling calculations (E. M. Goldfield and A. J. H. M. Meijer, J. Chem. Phys., 2000, 113, 11055). Our results show significant deviations from the close coupling reaction probabilities for all approximations studied. As a result the approximate cross sections do not agree very well with the close coupling cross sections. We also compare our results to an approximate J-s hifting type method due to Varandas (A. J. C. Varandas, Mol. Phys., 1995, 8 5, 1159). Our comparisons show the deficiencies of the different approximat e methods for this reaction and emphasize the need to perform rigorous calc ulations.