Issue 21, 2014

The nature of coherences in the B820 bacteriochlorophyll dimer revealed by two-dimensional electronic spectroscopy

Abstract

Light-harvesting in photosynthesis is determined by the excitonic interactions in disordered antennae and the coupling of collective electronic excitations to fast nuclear motions, producing efficient energy transfer with a complicated interplay between exciton and vibrational coherences. Two-dimensional electronic spectroscopy (2DES) is a powerful tool to study the presence of these coherences in photosynthetic complexes. However, the unambiguous assignment of the nature of the observed coherences is still under debate. In this paper we apply 2DES to an excitonically coupled bacteriochlorophyll dimer, the B820 subunit of the light harvesting complex 1 (LH1-RC) of R. rubrum G9. Fourier analysis of the measured kinetics and modeling of the spectral responses in a complete basis of electronic and vibrational states allow us to distinguish between pure vibrational, mixed exciton-vibrational (vibronic), and predominantly exciton coherences. The mixed coherences have been found in a wide range of oscillation frequencies, whereas exciton coherences give the biggest contributions for the frequencies in the 400–550 cm−1 range, corresponding to the exciton splitting energy of the B820 dimer. Significant exciton coherences are also present at higher frequencies, i.e., up to 800 cm−1, which are determined by realizations of the disorder with a large energy gap between the two pigments (which increases the apparent value of the exciton splitting). Although the B820 dimer is a model system, the approach presented here represents a basis for further analyses of more complicated systems, providing a tool for studying the interplay between electronic and vibrational coherences in disordered photosynthetic antennae and reaction centres.

Graphical abstract: The nature of coherences in the B820 bacteriochlorophyll dimer revealed by two-dimensional electronic spectroscopy

Supplementary files

Article information

Article type
Paper
Submitted
01 nov. 2013
Accepted
16 dic. 2013
First published
18 dic. 2013

Phys. Chem. Chem. Phys., 2014,16, 9930-9939

The nature of coherences in the B820 bacteriochlorophyll dimer revealed by two-dimensional electronic spectroscopy

M. Ferretti, V. I. Novoderezhkin, E. Romero, R. Augulis, A. Pandit, D. Zigmantas and R. V. Grondelle, Phys. Chem. Chem. Phys., 2014, 16, 9930 DOI: 10.1039/C3CP54634A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements