Coupled channel distorted wave calculations for the three-dimensional H+H/sub 2/ reaction

Journal Article · Sun Jul 01 04:00:00 EDT 1984 · J. Chem. Phys.; (United States)

OSTI ID:6672670

Schatz, G C; Hubbard, L M; Dardi, P S; Miller, W H

A method for determining cross sections and other dynamical information based on the use of accurate coupled channel nonreactive wave functions in an evaluation of the distorted wave reactive scattering amplitude is developed for three-dimensional atom--diatom reactive collisions and applied to the H+H/sub 2/ reaction. The nonreactive wave functions are obtained by using a truncated expansion in asymptotic vibration/rotation states to generate coupled channel equations in terms of the full Hamiltonian. Explicit reduction of the distorted wave scattering matrix expression to a real valued three-dimensional integral is given and methods for simplifying the calculation through the use of parity decoupling, even/odd decoupling, and the coupled states approximation are introduced. The application to H+H/sub 2/ considers the Porter--Karplus potential surface. Comparison of reaction probabilities, opacity functions, differential and integral cross sections with corresponding results from exact quantum calculations indicates that the coupled channel distorted wave method is an excellent approximation as long as the total reaction probability for each partial wave is less than 0.1. This upper limit occurs at 0.60 eV total energy for H+H/sub 2/. Above that energy, convergence with basis set size is oscillatory after an initial plateau. The coupled states distorted wave method is also found to be an excellent approximation, with results which are indistinguishable in accuracy from coupled channel distorted wave results. Extension of these approaches to a nonperturbative evaluation of the scattering matrix elements is discussed.

• Research Organization: Department of Chemistry, Northwestern University, Evanston, Illinois 60201
• OSTI ID: 6672670
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 81:1; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
AMPLITUDES
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
CHEMICAL REACTIONS
COLLISIONS
COUPLED CHANNEL THEORY
CROSS SECTIONS
DISTORTED WAVE THEORY
ELEMENTS
FUNCTIONS
HYDROGEN
MATRIX ELEMENTS
MOLECULE COLLISIONS
NONMETALS
SCATTERING AMPLITUDES
WAVE FUNCTIONS