Nonadiabatic semiclassical scattering: Atom--diatom collisions in self-consistent matrix propagator formalism
The self-consistent matrix propagator method of Laing and Freed is extended to treat semiclassical nonadiabatic scattering in the collinear atom--diatom system. Applications are made to a model system in which diabatic surfaces are parallel, so the nonadiabatic transitions are not well localized in space, thereby introducing difficulties in some previous nonadiabatic semiclassical methods. In the self-consistent matrix propagator method nonadiabatic transitions occur at the boundaries of Magnus regions, and the relative phases, associated with trajectories undergoing transitions at different boundaries, must accurately be determined. This necessitates the determination of the absolute phases of the uniformized classical S matrix, a phase which is unnecessary in single potential surface semiclassical scattering. Semiclassical calculations are compared with full close coupled quantum calculations of Schmalz. The agreement is very good even at relatively low energies. The largest errors enter, as anticipated, for highly classically forbidden transitions whose overall probabilities are, however, rather small. The self-consistent matrix propagator method becomes simpler to apply and more accurate as the total energy increases, i.e., as the fully quantum calculations become prohibitively large. The method has the physical appeal that the self-consistent trajectories follow essentially adiabatic surfaces in strongly interacting regions and diabatic surfaces in weakly interacting regions, with a self-consistent interpolation between these regions.
- Research Organization:
- Department of Chemistry and Quantum Theory Group, Tulane University, New Orleans, Louisiana 70118
- OSTI ID:
- 6238731
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 78:10
- Country of Publication:
- United States
- Language:
- English
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