Analytic continuation of real-time correlation functions to obtain thermal rate constants for chemical reaction

It is shown how a particular correlation function, computed quantum mechanically or semiclassically as a function of real-time, can be analytically continued to obtain thermal rate constants (or other thermally averaged quantities) over a wide range of temperature. The correlation function is first evaluated at a reference temperature, and then analytically continued to obtain information at other desired temperatures. The method is applied to the calculation of the thermal rate constant for the Cl + H-2 --> HCl + H (J = 0) reaction using the flux correlation function formalism, and it is seen to be capable of obtaining accurate rate constants over a broad temperature range. (C) 1999 Elsevier Science B.V. All rights reserved.