title: The flux-flux correlation function for anharmonic barriers.
abstract: The flux-flux correlation function formalism is a standard and widely used approach for the computation of reaction rates. In this paper we introduce a method to compute the classical and quantum flux-flux correlation functions for anharmonic barriers essentially analytically through the use of the classical and quantum normal forms. In the quantum case we show that for a general f degree-of-freedom system having an index one saddle the quantum normal form reduces the computation of the flux-flux correlation function to that of an effective one-dimensional anharmonic barrier. The example of the computation of the quantum flux-flux correlation function for a fourth order anharmonic barrier is worked out in detail, and we present an analytical expression for the quantum mechanical microcanonical flux-flux correlation function. We then give a discussion of the short-time and harmonic limits.
authors.affiliation: School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW, United Kingdom.
authors.forename: Arseni
authors.initials: A
authors.lastname: Goussev
authors.forename: Roman
authors.initials: R
authors.lastname: Schubert
authors.forename: Holger
authors.initials: H
authors.lastname: Waalkens
authors.forename: Stephen
authors.initials: S
authors.lastname: Wiggins