Spectral diffusion in orientationally disordered organic solids

The spectral diffusion within the inhomogeneous line width of the T₁ ← S₀ transition is presented for an orientationally disordered organic solid under the condition when kT (∼3 cm^-1) is much smaller than the inhomogeneous line width (∼83 cm^-1). The rate of the transfer is found to increase as the site energy increases. This result is explained in terms of a phonon-assisted unidirectional (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.