Title

Barrier Resonances and Chemical Reactivity

Document Type

Article

Publication Date

1997

Publication Source

Multiparticle Quantum Scattering With Applications to Nuclear, Atomic and Molecular Physics

Volume

89

Inclusive pages

243-281

DOI

10.1007/978-1-4612-1870-8_9

ISBN/ISSN

Print: 978-1-4612-7318-9 , Online: 978-1-4612-1870-8 , ISSN: 0940-6573

Abstract

We survey the phenomenology of broad and overlapping resonances in the scattering theory of molecular collisions. We first discuss examples of resonances encountered in molecular collisions that are not described by the well known isolated narrow resonance formulae; nevertheless certain regularities are observed. We emphasize (i) the relationship between the total resonance width and the sum of the partial widths and (ii) the comparison of trapped-state resonances to barrier resonances, especially from the point of view of the change in background (direct) scattering over the width of the resonance. We then focus on quantal scattering by one-dimensional potential energy functions to provide further insight into the nature of barrier resonances, which are also called transition states. In studies of symmetric and unsymmetric potential functions, we show that reaction thresholds associated with barriers are associated with poles of the scattering matrix; i.e., chemical reaction thresholds are resonances. As the parameters of the potential function are varied, we follow the“trajectory” of the poles in the complex energy plane and examine the connection between barrier resonances and conventional resonances associated with wells between barriers. Resonances are further characterized by considering the relationship between the resonance width and the reactive delay time.

Keywords

chemical reactions poles of the scattering matrix resonances spectroscopy of the transition state

Disciplines

Chemistry

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