Fluorescence-detected two-dimensional electronic spectroscopy: A coarse-grained simulation approach.

Area of Science:

• Physical Chemistry
• Spectroscopy
• Photosynthesis Research

Background:

• Fluorescence-detected two-dimensional electronic spectroscopy (F-2DES) offers higher sensitivity than traditional coherent two-dimensional electronic spectroscopy (2DES).
• Theoretical modeling is crucial for interpreting F-2DES spectra, particularly for complex multi-chromophoric systems.
• Conventional 2DES faces computational challenges for large molecular assemblies, limiting its application in excitation energy transfer studies.

Purpose of the Study:

• To extend a coarse-grained method for simulating F-2DES spectra.
• To incorporate the effects of exciton-exciton annihilation on F-2DES cross-peak intensities.
• To apply the enhanced simulation method to the light-harvesting II complex of purple bacteria.

Main Methods:

• Extension of a coarse-grained computational method for 2DES simulations.
• Inclusion of exciton-exciton annihilation signatures within the F-2DES simulation framework.
• Application and validation of the method using experimental data from the light-harvesting II complex.

Main Results:

• The F-2DES simulations successfully reproduced experimental cross-peaks at zero and early waiting times for the light-harvesting II complex.
• Disabling exciton-exciton annihilation in simulations yielded results identical to standard 2DES, confirming annihilation's role in observed cross-peaks.
• The study validates the hypothesis that exciton-exciton annihilation significantly impacts F-2DES cross-peak intensities.

Conclusions:

• The developed coarse-grained method enables accurate theoretical modeling of F-2DES spectra, including annihilation effects.
• This approach facilitates the interpretation of complex spectroscopic data from photosynthetic systems.
• The method paves the way for predicting F-2DES spectra and exploring waiting-time dynamics in larger and more complex systems.