On the rate of triplet excitation transfer in the diffusive limit

✍ Scribed by Maria A. Davidovich; Robert S. Knox

• Publisher: Elsevier Science
• Year: 1979
• Tongue: English
• Weight: 378 KB
• Volume: 68
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(79)87223-1

✦ Synopsis

The useftdness of spectral data in estim;tting intermolecuhr triplet eacitation transfer mtes is found to be rather limited and to depend explicitly on the mechanisms which allow the optical transitions_ Necessar& conditions for the validiry of such use of spectra are given, and the othen\ise required correction factors are discussed and estimated. Dexter's expression [I] for the rate of triplet exciton transfer in the diffusive limit has been used in cakulations of transport quantities in organic crystals [Z-5]. It relates the rate of transfer of triplet excitation from molecule A to B, wAB, to the exchange interaction ener,T /3 between the molecules and to the normalized phosphorescence spectrum fA and triplet absorption spectrum FB of donor A and acceptor B as follows: (1) The connection with the spectra follows from the identification of the vibrational factors involved in the transfer with those occurring in the spectra of the moIecules_ A similar expression had been derived by Fikster [6] for the rate of transfer of singlet excitons with dipole allowed transitions, in which case the matrix eiements involved in the transfer and in the radiative transition of the molecules are the same. nameIy, those of a dipole interaction. However, in the case of triplet excitons, when the transfer is mediated by an exchange interaction the connection * Research supported in part by NSF grant PCM-77-20230_ Dr_ Davidovich acknowledges partial support by the Brazilian agency Conselho National de Pesquisas. * Based on part of a Ph.D_ thesis submitted to the University of Rochester.