Evaluation of thermal rate constants in the eigenbasis of a Hamiltonian with an optical potential

Journal Article · Thu Oct 15 04:00:00 EDT 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.463805· OSTI ID:7273724

Brown, D; Light, J C ^[1]

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1. The James Franck Institute and the Department of Chemistry, University of Chicag 60637 (United States)

Miller and co-workers (J. Chem. Phys. {bold 61}, 1823 (1974); {ital ibid}., {bold 79}, 4889 (1983)) have derived an exact quantum mechanical expression for reactive thermal rate constants in terms of the time integral of a flux autocorrelation function. The evaluation of this integral in a finite basis poses the problem that spurious oscillations in the correlation function due to recurrences can occur at long times, corrupting the result. To obviate this difficulty, we add to the Hamiltonian an optical potential in the asymptotic region, and evaluate eigenvalues and eigenvectors using the technique of successive truncation. These operations allow a diagonal (although nonorthogonal) representation of the propagator in which the eigenvalues are exponentially decaying functions of time, which damp the components of the propagated vectors before the spurious reflection back into the interaction region. In this manner, the infinite time limit of the integral may be evaluated properly. Furthermore, the results of a single diagonalization may be used to compute the thermal rate constant over a range of temperatures.

• DOE Contract Number: FG02-87ER13679
• OSTI ID: 7273724
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 97:8; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
661100 -- Classical & Quantum Mechanics-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ASYMPTOTIC SOLUTIONS
CHEMICAL REACTIONS
CORRELATION FUNCTIONS
EIGENVALUES
FUNCTIONS
HAMILTONIANS
INTEGRALS
MATHEMATICAL OPERATORS
MECHANICS
OPTICAL MODELS
POTENTIALS
PROPAGATOR
QUANTUM MECHANICS
QUANTUM OPERATORS