For the singlet-singlet annihilation process S1S1S2S0, an expression is derived for the electronic coupling matrix element involved in electronic excitation energy transfer (EET) between two equivalent chromophores. Allowance is made for vibronic coupling to occur between the S1 and S2 states of the chromophores, for each of which the S1←S0 and S2←S0 excitations are, respectively, electric-dipole forbidden and allowed. Attention is also given to aspects of the theory for singlet-singlet (πDπD*) (nAnA)→(πDπD) (nAπA*) EET with vibronic coupling. The theory for S1S1→S2S0 is illustrated via the results of some model calculations for two CS chromophores. For each chromophore, the calculations treat explicitly the valence-shell pπ atomic orbitals and a sulphur lone-pair atomic orbital. The results of the calculations highlight the nature of the primary contributors to the vibronic coupling component of the electronic EET matrix element, namely Coulombic-type terms. The theory also shows that a Coulombic term is the primary contributor to the vibronic coupling component for singlet-singlet (πDπD*) (nAnA)→(πDπD) (nAπA*) EET.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry