Effects of anharmonicity and electronic coupling on photoinduced electron transfer in mixed valence compounds

Daren M. Lockwood, Mark A. Ratner, Ronnie Kosloff
2002 Journal of Chemical Physics  
We develop a semigroup model of electron transfer ͑ET͒ dynamics in mixed valence compounds. This model is useful for investigating the effects of anharmonicity in inner sphere nuclear modes, as well as the dependence of the electronic dynamics on the nature of the electronic coupling. Two effective "subsystem" nuclear vibrations are treated explicitly in the model, to account for the rapid electronic energy gap fluctuations induced by the inner sphere vibrations. The essentially Markovian
more » ... lly Markovian effects of the remaining "bath" modes are approximated by semigroups. We find that including the anharmonicity in inner sphere vibrations leads to a very small increase in the rate of ET. This effect is due to the change in reactant and product vibronic states when anharmonicity is included, as well as the rapid electronic dephasing induced by the bath. An assumption of strong electronic coupling is found to be sufficient to explain experimentally observed ET rates, but the possible role of conical intersections in ultrafast ET reactions is also noted. The Hamiltonian governing ET in compounds such as (NH 3 ͒ 5 RuNCRu͑CN͒ 5 Ϫ can be written as Ĥ ϭJ͉͑A͗͘D͉ϩ͉D͗͘A͉͒ϩ͉D͘H D ͗D͉ϩ͉A͘H A ͗A͉, ͑1͒ a͒ Electronic
doi:10.1063/1.1519258 fatcat:ahic2yqaznb5xpdgri6w43zun4