Tunneling in the F+H2 reaction and its isotopic variants: the effect of the Van der Waals potential

Cumulative reaction probabilities have been calculated for the F+H2, D2 and HD reactions using the three-dimensional quantum scattering method with an emphasis on the threshold behavior of the reaction probabilities. The accurate ab initio potential energy surface of Stark–Werner has been employed. We found small probability peaks just above the reaction threshold for the F+H2 and D2 reactions. These peaks are attributed to the quasi-bound resonance states localized in the reactant Van der Waals well. The results for F+HD also show that the Van der Waals potential plays an important role in reaction dynamics.