Excitons in Chains of Dimers

Abstract

Excitons in circular aggregates of dimers are discussed with the aim to understand the possible spectral and energy transfer properties of the ringlike peripheral complexes of photosynthetic bacteria. The system is explicitly heterogeneous (i.e., the difference in transition energies of the molecules within the dimer as, well as the difference in the intra-and interdimer resonance interactions, is accounted for). It is demonstrated that the energy spectrum of such a system exhibits many of the features as observed in spectrally inhomogeneous circular aggregates. The model is used to illustrate the changes in absorption and circular dichroism spectra that take place upon incorporating a dimer into a circular chain. The exciton dynamics in the aggregate is considered in the Haken-Strobl-Reineker approach. When terms are neglected describing the phase relaxation between nonnearest neighbors, the equations for the diagonal density matrix elements are obtained containing both coherent exciton motion within the dimersthe building block of the aggregatesand an incoherent hopping of the excitation between dimers. It is demonstrated that these equations contain a wavelike soliton solution (if dephasing is absent) as well as a diffusion-like solution (for large dephasing rates).

Local and Nonlocal Contributions to the Linear Spectroscopy of Light-Harvesting Antenna Systems

“…For the unperturbed ring of pigments we would get for the amplitude of F 11,12 (ω)/F 11,11 (ω) at frequency ω k using the results of the Appendix This cosine-type behavior is still clearly visible in Figure 4b; only the amplitude was reduced from 1 to a lower value of approximately 0.7. Similar considerations hold for the other curves.…”

“…It can therefore be viewed as a ring of dimers. 12 However, in this paper we will develop a description in which the B850 ring can best be considered as a dimer of rings. The coupling between the rings can be expressed analytically in the coupling between all monomers, not just nearest neighbors.…”

Exciton (De)Localization in the LH2 Antenna of Rhodobacter sphaeroides As Revealed by Relative Difference Absorption Measurements of the LH2 Antenna and the B820 Subunit

“…We also performed calculations using alternative choices for the interaction energies: M 12 ) 300 and 500 cm -1 instead of M 12 ) 400 cm -1 , used in Figure 1. For both these alterations of M 12 we performed a corresponding scaling of M 23 , M 13 , and M 14 . Taking these interaction energies, it was possible to reproduce the ratio of the bleaching amplitudes of the LH2 antenna and the B820 dimeric subunit using approximately the same σ/M 12 value, i.e., taking σ ) 340 and 550 cm -1 for M 12 ) 300 and 500 cm -1 , respectively.…”

Polarized optical spectroscopy applied to investigate two poly(phenylene-vinylene) polymers with different side chain structures

“…28 In addition, experimental spectra have been analyzed using a framework of exciton theory, resulting in a detailed understanding of the optical properties of these systems. 29,30 CD spectroscopy on LEPs has also been used in a few cases. These studies have indicated strong interactions and exciton delocalization, mainly in the solid state ͑films͒.…”