An adiabatic analysis of the reactive infinite order sudden approximation

Abstract

A vibrationally adiabatic infinite order sudden approximation (IOSA) is formulated in terms of angle dependent adiabatic barriers. These barriers are determined by half-integer action periodic orbits. We show that in the F+HH reaction, the adiabatic theory describes quantitatively the exact IOSA total reactive cross section over a relatively large range of translational energies. A detailed analysis points out why in many cases transition state theory becomes more accurate as one goes from the collinear to the 3D world. Inversion of the quasiclassical IOSA provides a good estimate of the angular dependence of the adiabatic barrier parameters.