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Coupling to Charge Transfer States is the Key to Modulate the Optical Bands for Efficient Light Harvesting in Purple Bacteria

Authors :
Stefano Caprasecca
Frank Müh
Lorenzo Cupellini
Thomas Renger
Ciro A. Guido
Benedetta Mennucci
Source :
The Journal of Physical Chemistry Letters. 9:6892-6899
Publication Year :
2018
Publisher :
American Chemical Society (ACS), 2018.

Abstract

The photosynthetic apparatus of purple bacteria uses exciton delocalization and static disorder to modulate the position and broadening of its absorption bands, leading to efficient light harvesting. Its main antenna complex, LH2, contains two rings of identical bacteriochlorophyll pigments, B800 and B850, absorbing at 800 and 850 nm, respectively. It has been an unsolved problem why static disorder of the strongly coupled B850 ring is several times larger than that of the B800 ring. Here we show that mixing between excitons and charge transfer states in the B850 ring is responsible for the effect. The linear absorption spectrum of the LH2 system is simulated by using a multiscale approach with an exciton Hamiltonian generalized to include the charge transfer states that involve adjacent pigment pairs, with static disorder modeled microscopically by molecular dynamics simulations. Our results show that sufficient inhomogeneous broadening of the B850 band, needed for efficient light harvesting, is only obtained by utilizing static disorder in the coupling between local excited and interpigment charge transfer states.

Details

ISSN :
19487185
Volume :
9
Database :
OpenAIRE
Journal :
The Journal of Physical Chemistry Letters
Accession number :
edsair.doi.dedup.....43204966707c1c9afaee1c6515a03a68
Full Text :
https://doi.org/10.1021/acs.jpclett.8b03233