Electron–phonon and vibronic couplings in the FMO bacteriochlorophyll a antenna complex studied by difference fluorescence line narrowing

Rätsep, Margus; Freiberg, Arvi

doi:10.1016/j.jlumin.2007.02.053

Cited by 135 publications

(196 citation statements)

References 24 publications

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“…For FMO, several Franck-Condon active vibrations are found with frequencies in the range of 0 to 350 cm −1 [11,19]. Similar low-frequency phonons contribute to the observed dynamics of retinal proteins involved in vision [20,21].…”

Section: Introductionmentioning

confidence: 72%

Laser-Limited Signatures of Quantum Coherence

et al. 2015

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The observation of persistent oscillatory signals in multidimensional spectra of proteinpigment complexes has spurred a debate on the role of coherence-assisted electronic energy transfer as a key operating principle in photosynthesis. Vibronic coupling has recently been proposed as an explanation for the long lifetime of the observed spectral beatings. However, photosynthetic systems are inherently complicated, and tractable studies on simple molecular compounds are in demand to fully understand the underlying physics. In this work, we present measurements and calculations on a solvated molecular homodimer with clearly resolvable oscillations in the corresponding twodimensional spectra. Through analysis of the various contributions to the nonlinear response, we succeed in isolating the signal due to inter-exciton coherence. We find that while calculations predict a prolongation of this coherence due to vibronic coupling, the combination of dynamic disorder and vibrational relaxation leads to a coherence decay on a timescale comparable to the electronic dephasing time.

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Section: Introductionmentioning

confidence: 72%

Laser-Limited Signatures of Quantum Coherence

et al. 2015

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“…13 modes were combined between frequencies 1.31 × 10 14 Hz and 1.47 × 10 14 Hz to form the single bath mode modelled by the Hamiltonians in Eqs. (37) and (38). The frequency of the effective mode is given by the mean frequency and the Huang-Rhys factor is given by the sum of the Huang-Rhys factors of the selected modes (this commonly used approach 34,37,67 conserves the average number of quanta excited in the bath).…”

Section: Structured Spectral Densitymentioning

confidence: 96%

“…11,[27][28][29][30][31][32][33] In some pigment-protein complexes, these modes show significant coupling to the excitons. [34][35][36][37] This has led to theoretical studies that provide evidence for the important role they may play in assisting energy transport and in producing the long-lived coherences seen in 2D spectroscopy experiments. [27][28][29][30][31][32][33] The phenomenon whereby these underdamped molecular vibrations induce long-lived coherences and drive transitions between excitonic eigenstates has been demonstrated using a semi-classical treatment of the intra-molecular mode, 28 which it was claimed demonstrates that the fundamental mechanism is not dependent upon non-Markovian dynamics.…”

Section: Introductionmentioning

confidence: 99%

How Markovian is exciton dynamics in purple bacteria?

Vaughan

Linden

Manby

2017

The Journal of Chemical Physics

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We investigate the extent to which the dynamics of excitons in the light-harvesting complex LH2 of purple bacteria can be described using a Markovian approximation. To analyse the degree of non-Markovianity in these systems, we introduce a measure based on fitting Lindblad dynamics, as well as employing a recently introduced trace-distance measure. We apply these measures to a chromophore-dimer model of exciton dynamics and use the hierarchical equation-of-motion method to take into account the broad, low-frequency phonon bath. With a smooth phonon bath, small amounts of non-Markovianity are present according to the trace-distance measure, but the dynamics is poorly described by a Lindblad master equation unless the excitonic dimer coupling strength is modified. Inclusion of underdamped, high-frequency modes leads to significant deviations from Markovian evolution in both measures. In particular, we find that modes that are nearly resonant with gaps in the excitonic spectrum produce dynamics that deviate most strongly from the Lindblad approximation, despite the trace distance measuring larger amounts of non-Markovianity for higher frequency modes. Overall we find that the detailed structure in the high-frequency region of the spectral density has a significant impact on the nature of the dynamics of excitons.

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“…19, along with many later works [7][8][9][10][11][12][13][14][15][16][17][18] ). Although such a profile does provide a reasonable approximation to the true form of l R (ω) at low temperatures when the Gaussian and Lorentzian components have similar widths, the approximation breaks down quite seriously when Γ G is much different from √ RΓ L (see below).…”

Section: Derivation Of Lineshape Formulasmentioning

confidence: 97%

Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

Reppert

Kell

Pruitt

et al. 2015

The Journal of Chemical Physics

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The vibrational spectral density is an important physical parameter needed to describe both linear and non-linear spectra of multi-chromophore systems such as photosynthetic complexes. Low-temperature techniques such as hole burning (HB) and fluorescence line narrowing are commonly used to extract the spectral density for a given electronic transition from experimental data. We report here that the lineshape function formula reported by Hayes et al. [J. Phys. Chem. 98, 7337 (1994)] in the mean-phonon approximation and frequently applied to analyzing HB data contains inconsistencies in notation, leading to essentially incorrect expressions in cases of moderate and strong electron-phonon (el-ph) coupling strengths. A corrected lineshape function L(ω) is given that retains the computational and intuitive advantages of the expression of Hayes et al. [J. Phys. Chem. 98, 7337 (1994)]. Although the corrected lineshape function could be used in modeling studies of various optical spectra, we suggest that it is better to calculate the lineshape function numerically, without introducing the mean-phonon approximation. New theoretical fits of the P870 and P960 absorption bands and frequency-dependent resonant HB spectra of Rb. sphaeroides and Rps. viridis reaction centers are provided as examples to demonstrate the importance of correct lineshape expressions. Comparison with the previously determined el-ph coupling parameters [Johnson et al., J. Phys. Chem. 94, 5849 (1990); Lyle et al., ibid. 97, 6924 (1993); Reddy et al., ibid. 97, 6934 (1993)] is also provided. The new fits lead to modified el-ph coupling strengths and different frequencies of the special pair marker mode, ωsp, for Rb. sphaeroides that could be used in the future for more advanced calculations of absorption and HB spectra obtained for various bacterial reaction centers.

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Electron–phonon and vibronic couplings in the FMO bacteriochlorophyll a antenna complex studied by difference fluorescence line narrowing

Cited by 135 publications

References 24 publications

Laser-Limited Signatures of Quantum Coherence

Laser-Limited Signatures of Quantum Coherence

How Markovian is exciton dynamics in purple bacteria?

Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

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