van der Waals resonances in cumulative reaction probabilities for the F+H2, D2, and HD reactions

We present accurate quantum cumulative reaction probabilities for the F+H-2, D-2, and HD reactions with a special emphasis on resonances associated with quasibound states localized in the reactant van der Waals region of the potential energy surface. The accurate ab initio potential surface of Stark and Werner and the less accurate 5SEC-W surface developed by Truhlar and co-workers have been employed. The van der Waals resonance states which occur in the tunneling region can dissociate into the product channel, while the van der Waals resonance states at the classical region dissociate into the reactant channel. This indicates that prereaction effectively occurs in the tunneling region. It has been found that the van der Waals resonance states can be accurately assigned with the eigenvalues calculated with one-dimensional adiabatic potential energy curves. (C) 1998 American Institute of Physics. [S0021-9606(98)00244-X].