New approach to quantum mechanical transition-state theory

Abstract

Classical transition-state theory is based on the direct, short-time (actually, zero time) classical dynamics through a dividing surface that separates reactants and products. This paper defines a new quantum mechanical version of transition-state theory by using the reactive flux correlation function of Miller, Schwartz, and Tromp (J. Chem. Phys. 1983, 79, 4889) to identify the short-time quantum dynamics through the dividing surface. It is seen that short time quantum mechanically is not zero time, as it is classically, but rather a time of order Planck's constant..beta... This new quantum version of transition-state theory is also seen to have some of the variational character of the classical case. Finally, it is shown how the reactive flux correlation function of Miller, Schwartz, and Tromp can be generalized by choosing various forms of the projector onto reactants, and this is seen to have important consequences for the accuracy of this new quantum transition-state theory.