Spectral diffusion in orientationally disordered organic solids

The spectral diffusion within the inhomogeneous linewidth of the T1 from S0 transition is presented for an orientationally disordered organic solid under the condition when kT (approx. 3/cm) is much smaller than the inhomogeneous linewidth (approx. 83/cm). The rate of the transfer is found to increase as the site energy increases. This result is explained in terms of a phonon assisted undirectional (high to low) energy transfer process in which the increasing density of the low energy sites (acceptors) with an increase in the excitation energy plays an important role.