Exciton-migration and three-pulse femtosecond optical spectroscopies of photosynthetic antenna complexes

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Abstract
Exactly, whereas the phonon-dependence of the off-diagonal coupling ~which is responsible for exciton hopping! has been neglected. This approximation may be used in the calculation of two-pulse four-wave-mixing signals which are not sensi- tive to exciton migration. In this paper we extend the theory of Ref. 21~a! to in- clude exciton transfer. The effect of strong exciton-phonon coupling is described using an exciton-hopping superopera- tor calculated perturbatively in the off-diagonal exciton- phonon coupling. Since the diagonal exciton-phonon cou- pling is treated nonperturbatively, polaron formation and the nuclear reorganization energies are properly incorporated, in full analogy with Marcus electron transfer theory. 22 The sig- natures of exciton population dynamics in three-pulse echo and pump-probe measurements in light-harvesting antenna complexes are then explored using this theory. The paper is organized as follows: In Section II we