A test of the semiclassical Wigner method for the reaction F + H2 → H + HF Original Research Article

We compute the vibrationally resolved integral cross sections σR(ν′), differential cross sections, and opacity functions for the reaction F + H2(ν = 0, j = 0, 1) → H + HF(ν′, j′) on the 6SEC potential energy surface by the quasiclassical trajectory technique as well as the Wigner method. In both cases, the Langer correction of the initial H2 rotational energy is implemented. The results are compared with the recent quasiclassical trajectory calculations on the same surface without the Langer correction and quantum mechanical calculations. It is shown that use of the Wigner phase space functions to describe the H2 and HF vibrational degrees of freedom reduces the total integral cross sections, smooths the selective HF(ν′ = 3) forward peak in the HF center-of-mass angular distributions, and dramatically increases the σR(ν′ = 3)/σR(ν′ = 2) vibrational branching ratio. These results indicate that the disagreements between the quasiclassical trajectory cross sections and the quantum mechanical ones observed in the previous works cannot be minimized by just a proper choice and weighting of the initial conditions in the quasiclassical trajectory calculations.