Electronic energy transfer in impure solids: I. Two molecules embedded in a lattice

In the present paper we consider the transfer of electronic excitation energy between two molecules embedded in a host lattice. We use a simple model for the electron phonon coupling and solve for the density matrix of the electronic system in the absence of radiative decay. We find, in the weak coupling limit, that the approach to equilibrium is in general complex but for large transfer rates becomes a simple exponential.