ENERGY RELAXATION AND TRANSFER IN TRIMER

Abstract

We consider the relaxation and transfer in a symmetric trimer coupled to a phonon bath. The energy transfer within the trimer occurs via resonance interactions and coupling between the trimer and the bath occurs via modulation of the monomer energies by phonons. We compare the model introduced by Čápek with the Redfield model used commonly with secular approximation. We discuss two initial conditions: a) The highest eigenstate of the trimer is initially excited, and b) the initial excitation is local. We find that the occupation probabilities in the representation of eigenstates are the same in both models. But it is not so for off-diagonal density matrix elements. Only if the off-diagonal elements vanish initially (initial conidtion a), they vanish at arbitrary time in both models. If the initial excitation is local, off-diagonal elements differ essentially even in the long time limit.