Monopole effects on electronic excitation interactions between large molecules. I. Application to energy transfer in chlorophylls

The transition monopole theory of electronic excitation interaction is described and applied to the theory of resonance transfer for chlorophyll molecules. It is then compared with analogous results based on transition dipole theory. The correction to the Förster theory of resonance transfer is evaluated in various geometries for the case of short range transfer. The enhancement or reduction factor for the transfer rate in various chlorophylls is of the order of two to one tenth for the range that we are interested in, i.e., 12–30 Å, and anisotropy of the transfer rate is greatly increased. A possible enhancement of the transfer rates in the case of forbidden transitions in porphin is discussed.