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Pump-probe spectroscopy and the exciton delocalization length in molecular aggregates

Article Abstract:

Numerical simulations were performed to examine the feasibility of the pump-probe spectrum as a tool to measure the exciton delocalization length in molecular J aggregates with static disorder of different strengths. Results suggested that the typical delocalization length can be accurately measured with the pump-probe spectrum, but not the energy dependence within the J band. It was also observed that a smaller slope results with the increasing width of the probe pulse. However, the slope stays close to unity when the probe pulse is narrower that the J band.

Molecular dynamics

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Exciton coupling in the photosystem I reaction center

Article Abstract:

Research was conducted to examine the electronic structure of the photosynthetic reaction center (RC) of photosystem I (PSI) based on the x-ray structure of Synechococcus elongatus. By generating the MO's of the Chl, Chl+ and Chl- molecules, the absorption spectrum of the PSI RC was estimated in three oxidation states. Results indicate that the state giving rise to the absorption of the special pair is partly extended over the other molecules in the R C but will be localized by disorder.

Electronic structure, Atomic structure

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Approaches to calculation of exciton interaction energies for a molecular dimer

Article Abstract:

The sum over Coulombic interactions between atomic transition charges is compared to the point-dipole and extended-dipole approximations and to the direct evaluation of the Coulomb interaction integral over transition charge densities, for a range of dimer configurations. Further, the relation of interaction energies to the calculated supermolecular approach is discussed.

Science & research, Electrostatic interactions, Coulomb excitation

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