Computational Methods for Reactive Scattering

Two methods of obtaining unimodular sector transformation matrices required in quantum scattering calculations employing locally adiabatic basis sets are discussed, one being particularly useful for three-dimensional reactive scattering. These are shown to lead to improved unitarity and detailed balance in a computed S-matrix. New results arc presented for the H + D2, and F + H2 reactions, including total cross sections obtained within a J2-conserving approximation. In particular, evidence is presented which indicates that the strong n = 2 vibrational resonance appearing in collinear studies of the F + H2 reaction is drastically affected by rotational broadening, indicating that collinear studies of exoergic reactions may be of limited practical utility in predicting resonance widths.