ABSTRACT: We derived a convenient expression of the rate constant for
nonadiabatic transitions, with the intention of making it possible and practical to
calculate the rate constant. For this derivation, we first assume that the seam, at which
the adiabatic potential energy surfaces of reactant and product electronic states exhibit
an avoided crossing, corresponds to the dividing surface of the nonadiabatic transition.
Second, we use the probability that a nonadiabatic transition occurs in the seam. Third,
the partition function in the seam is described by the local profile of the adiabatic
potential energy surfaces of both the reactant and product electronic states. The rate
constant expression thus derived not only gives significant insight into understanding
nonadiabatic transitions, but also makes it possible to obtain a rough estimate of the
rate constant. ©2004 Wiley Periodicals,Inc.Int J Quantum Chem 102: 8-18, 2005
Key words: nonadiabatic transition; rate constant; transition state theory; excitation
energy transfer; parphyrin wire