Dynamical Formulation of Transition State Theory: Variational Transition States and Semiclassical Tunneling

Abstract

This paper is an introduction to recent research in generalized transition state theory. We derive the theory by considering the equilibrium flux through a surface dividing reactants from products, and we show its equivalence to the quasi-thermodynamic formulation of transition state theory. We show that conventional transition state theory is obtained from the generalized theory with a specific choice of dividing surface, but we stress that in many cases the variational identification of the transition state provides significant improvement. We discuss methods for including quantum effects, with special attention to the semiclassical treatment of tunneling. We briefly review tests of the theory and applications to gas-phase, condensed-phase, and interface reactions. Finally we discuss the importance of nonsubstantial contributions to quasi-thermodynamic quantities.