Comment on 'On the high pressure rate constants for the H/Mu + O_2 addition reactions' by J. M. C. Marques and A. J. C. Varandas, Phys. Chem. Chem. Phys., 2001, 3, 505

摘要

In a recent Communication, Marques and Varandas report classical trajectory (CT) calculations for the high pressure addition reactions H + O_2 → HO_2 and muonium + O_2 → MuO_2 using the double many-body expansion (DMBE IV) potential from ref. 2. Part of the motivation for this study came from the observation in our own work that the DMBE IV and our ab initio potential differ in regions relevant for the capture dynamics such that different high pressure rate coefficients k_(rec,∞) should be expected. Investigating this suggestion, Marques and Varandas show that their CT results using the DMBE IV potential for the H + O_2 reaction at T = 400-2000 K within ±10% agree with our results based on the ab initio potential. On the other hand, their results fall markedly below our results at lower temperatures, being about a factor of 2 lower at T → 30 K. On the basis of these results and the available experimental data they conclude that the global DMBE IV potential is accurate enough to study H + O_2 and Mu + O_2 capture rates. In addition they suggest that our results for low temperatures "should be seen with caution" because, in contrast to their fully dimensional potential, we used a "2D potential", i.e. a potential with a rigid rotor O_2 molecule.