Evidence for coherent energy transfer in allophycocyanin trimers
- Vanderbilt Univ., Nashville, TN (United States)
We have performed two-color femtosecond pump-probe anisotropy experiments on allophycocyanin trimers, a photosynthetic light-harvesting system located at the core of the phycobilisome of cyanobacteria. The anisotropy decays in a multiexponential manner from an initial maximum in the 0.58-0.7 range, with components exhibiting time constants of 10-30 fs, 280 fs, and 1 ps. The observation that the initial anisotropy is significantly larger than 0.4 evidences the initial presence of coherently excited molecular dimers in allophycocyanin trimers. The 10-30-fs anisotropy component reports the time scale for interexciton state relaxation, while the slower components report the time scale for localization of excitation on one of the dimer chromophores; the rate constant for localization is expected to be comparable with that estimated for Foerster energy transfer between the two chromophores in a dimer. We suggest that the initial presence and decay of dimer electronic coherence might play a role in enhancing the energy-transfer function of allophycocyanin in the phycobilisome. 76 refs., 3 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 159720
- Journal Information:
- Journal of Physical Chemistry, Vol. 99, Issue 43; Other Information: PBD: 26 Oct 1995
- Country of Publication:
- United States
- Language:
- English
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