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

Rotational and vibrational distributions of zero-temperature collisional rate coefficients for atom-diatom scattering are used together with effective range theory to obtain lifetimes for predissociation. High-order indirect potential coupling in the quantum-mechanical calculation is interpreted using a simple classical picture that describes the quasiresonant dynamics of atom-diatom collisions by the conservation of classical action. The importance of closed channel thresholds in determining the structure of the distributions and the balance between momentum gap and near-resonant effects is discussed.