A Transition State Resonance Radically Reshapes Angular Distributions of the F + H2 → FH(vf = 3) + H Reaction in the 62–102 meV Energy Range

Reactive angular distributions of the benchmark F + H₂(v_i = 0) → FH(v_f = 3) + H reaction show unusual propensity toward small scattering angles, a subject of a long debate in the literature. We use Regge trajectories to quantify the resonance contributions to state-to-state differential cross sections. Conversion to complex energy poles allows us to attribute the effect almost exclusively to a transition state resonance, long known to exist in the F + H₂ system and its isotopic variant F + HD. For our detailed analysis of angular scattering we employ the package DCS_Regge, recently developed for the purpose [Akhmatskaya, E.; Sokolovski, D. Comput. Phys. Commun. 2022, 277, 108370].