Quantum mechanical and quasiclassical simulations of molecular beam experiments for the F+H2→HF+H reaction on two ab initio potential energy surfaces

Laboratory (LAB) angular distributions (AD) measured in molecular beam experiments by Lee and co-workers in 1985 and very recently by Keil and co-workers for the prototypic F+H-2 reaction have been simulated using new quantum mechanical (QM) and quasiclassical trajectory (QCT) state-resolved differential cross sections (DCS) calculated on the ab initio potential energy surfaces (PES) by Stark and Werner (SW) and by Hartke, Stark and Werner (HSW); the latter PES includes spin-orbit coupling corrections added to the entrance channel of the former. The simulations of the 1985 LAB ADs performed using the new QM calculations on the SW PES show a very good agreement with the experimental results for all final vibrational states of the HF product. The inclusion of spin-orbit coupling corrections in the ab initio HSW PES does not seem to improve the agreement between theoretical and experimental results. As for the simulation of the recent experiments of Keil and co-workers, the LAB ADs are very well reproduced by the QM and QCT results on both the SW and HSW PESs with the exception of the negative signal measured at LAB scattering angles of about -8 degrees, arising from HF scattering into the forward hemisphere for the v'=1, j'=5,6,7 states. This peak cannot be accounted for by either of the QM and QCT calculations on any of the two PESs. (C) 1998 American Institute of Physics.