Beyond Forster Resonance Energy Transfer in Linear Nanoscale Systems

The line dipole approximation is used to investigate analytical corrections to the Forster energy transfer rate, k, derived via the point dipole approximation. It is shown that that for molecules whose conjugation length, L, is much larger than the separation, R, between molecules the line dipole approximation predicts k similar to (RL)(-2) similar to (RN)(-2) (where N is the number of conjugated monomer units). This is in contrast to the point dipole approximation, which predicts k similar to (LR-6)-R-2 similar to (NR-6)-R-2.