Vibrational energy relaxation rate constants from linear response theory

Abstract

A new approach for the calculation of vibrational energy relaxation rate constants is introduced. The new approach is based on linear response theory, and is shown to have several distinct advantages over the standard Landau–Teller formula, which is based on the Bloch–Redfield theory, namely: (1) weak system–bath coupling is not assumed; (2) selectivity in choosing the vibrational energy relaxation pathway, including non-Landau–Teller pathways, is possible; (3) the validity of rate kinetics can be explicitly verified; (4) direct extraction of the high-frequency tail of the force–force correlation function is avoided. A detailed analysis of the conditions under which the new expression reduces into the Landau–Teller formula, and an application in the case of bilinear coupling to a harmonic bath are provided.