Unified approach to the quantum-Kramers reaction rate

The quantum analog of Kramers rate theory is derived from a unique many-body rate approach (Miller formula), being valid at all temperatures. In contrast to the imaginary free energy method (‘‘bounce’’ method) for a dissipative system we do not have to invoke a different prescription of the rate formula for temperatures below the crossover temperature T0 to tunneling dominated escape. Miller’s many-body quantum transition state theory is shown to produce the results of the imaginary free energy technique; in particular it also describes correctly the subtle regime near crossover T∼T0.