Simulating Fluorescence-Detected Two-Dimensional Electronic Spectroscopy of Multichromophoric Systems

Abstract

We present a theory for modeling fluorescence-detected two-dimensional electronic spectroscopy of multichromophoric systems. The theory is tested by comparison of the predicted spectra of the light-harvesting complex LH2 with experimental data. A qualitative explanation of the strong cross-peaks as compared to conventional two-dimensional electronic spectra is given. The strong cross-peaks are attributed to the clean ground-state signal that is revealed when the annihilation of exciton pairs created on the same LH2 complex cancels oppositely signed signals from the doubly excited state. This annihilation process occurs much faster than the nonradiative relaxation. Furthermore, the line shape difference is attributed to slow dynamics, exciton delocalization within the bands, and intraband exciton–exciton annihilation. This is in line with existing theories presented for model systems. We further propose the use of time-resolved fluorescence-detected two-dimensional spectroscopy to study state-resolved exciton–exciton annihilation.

Before Förster. Initial excitation in photosynthetic light harvesting

“…The argumentation is analogous to earlier work31–33 and follows the analyses of the third order optical response and the corresponding Liouville pathways represented here as double-sided Feynman diagrams 34. The different pathways of the rephasing and nonrephasing signals can be classified as ground state bleach (GSB), stimulated emission (SE) and excited state absorption (ESA).…”

Observation of Ultrafast Coherence Transfer and Degenerate States with Polarization-Controlled Two-Dimensional Electronic Spectroscopy

“…These parameters are slightly adjusted for better agreement with the linear absorption as compared to the values used previously. 36 The coupling was obtained by using the transition dipole coupling model. In this way, a 600 ps long trajectory of the Hamiltonian is created where the off-diagonal elements are constant as the location and orientation of the chromophores are fixed as defined by the pdb structure.…”

“… 2 , 41 The calculations were performed by using the same setting as in our previous study of F-2DES and 2DES with parallel polarization. 36 The most important simulation details are summarized in the following. The coherence times ( t 1 and t 3 ) were varied from 0 to 192 fs in 3 fs steps.…”

Interpreting Fluorescence Detected Two-Dimensional Electronic Spectroscopy

“…11 Even though 2DES and F-2DES are analogous coherent techniques providing detailed information on ultrafast dynamics in two spectral dimensions, the methods have important differences and the measured spectra do not look the same. 12,13,14,15 While the "anatomy" of the 2DES has been studied in numerous articles 16,17,18 and is quite well understood, interpretation of the F-2DES spectra 19,20,21,22,23 has not reached similar maturity and is currently being debated in literature. In this Viewpoint we briefly summarize the various approaches to interpreting the F-2DES and present our view with the intension to resolve at least some of the existing controversial issues.…”

“…13,36 On the other hand, the ESA2 -ESA1 cancellation (which reveals the cross peaks) takes place due to the exciton-exciton annihilation and thereby the cross peaks can be taken as signatures of the annihilation. 20,21 In case of individual LH2s where perfect annihilation is a well-established fact, the latter aspect is less of interest while the potential of the method for evaluating delocalization is more relevant. However, connectivity in large antenna complexes 48 can be possibly investigated via existence of annihilation witnessed by the F-2DES cross peaks.Finally, we point out that our considerations here may be relevant for the discussion of the twoparticle DQC signal observed in dilute gases.…”