Effect of quasiresonant dynamics on the predissociation of van der Waals molecules

A case was considered where the rotational period is short compared to the time required for the fragments to separate. For the most weakly bound state of the van der Waals complex, it was found that the process of predissociation is controlled by the same classical dynamical quasiresonant transfer of energy that is found in ultracold atom-diatom collisions. This finding was demonstrated by calculating zero-temperature quenching rate coefficients for He collisions with H₂ using the general purpose scattering program MOLSCAT and the potential energy surface of Muchnick and Russek. The rate coefficients were related to the predissociation lifetimes using the effective range theory. Threshold behavior was explained using a perturbative description of the scattering matrix elements.