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Bimolecular Reactive Collisions

1984; American Chemical Society; Linguagem: Inglês

10.1021/bk-1984-0263.ch020

1947-5918

Bruce C. Garrett, David W. Schwenke, Rex T. Skodje, Devarajan Thirumalai, Todd C. Thompson, Donald G. Truhlar,

Molecular Spectroscopy and Structure

Several approximate methods for calculating resonance energies and widths for atom-diatom reactive collisions are discussed. In particular, we present resonance energy calculations by semiclassical and quantal vibrationally adiabatic models based on minimum-energy and small-curvature paths, by the semiclassical SCF method, by quantal SCF and configuration-mixing methods, and by close coupling calculations. We also present total width calculations based on analytic continuation by polynomials and Padé approximants of configuration-mixing stabilization graphs, and we present total width and partial-width calculations based on close coupling calculations and on the Feshbach formalism in reaction-path coordinates with a small-curvature tunneling approximation for adiabatic decay and a reaction-path-curvature coupling operator for nonadiabatic decay. The model calculations are judged by their agreement with the accurate close coupling calculations, and we also compare the resonance energies and total widths to values obtained semiclassically from resonant periodic orbits. To illustrate the methods we consider the collinear reactions H + FH → HF + H and D + FD → DF + D on the low-barrier model potential of Muckerman, Schatz, and Kuppermann and the collinear and three-dimensional H + H2 reactions on Porter-Karplus surface number 2. Finally we use an accurate potential energy surface for the three-dimensional H + H2 reaction to predict the energies of several series of observable resonances for a real system.