Mapping the Evolution of Spatial Exciton Coherence through Time-Resolved Fluorescence.

Area of Science:

• Quantum mechanics
• Spectroscopy
• Biophysics

Background:

• Quantum coherence is theorized to enhance excitation energy transfer efficiency in photosynthetic aggregates and conjugated polymers.
• The precise role and significance of quantum coherence in these molecular systems remain largely uncharacterized.

Purpose of the Study:

• To propose and validate a novel experimental approach for monitoring quantum coherence between distant molecular sites.
• To establish a quantifiable relationship between a spectroscopic observable and the spatial extent of coherence.

Main Methods:

• Utilizing time-resolved fluorescence spectroscopy.
• Performing numerical calculations to correlate vibronic peak ratios with coherence range.
• Developing a method to monitor coherent evolution and dephasing over time.

Main Results:

• Demonstrated that the 0-0 to 0-1 vibronic peak ratio in time-resolved fluorescence spectroscopy directly scales with the spatial range of quantum coherence.
• Showcased the ability of this observable to track the initial large coherence length post-excitation and subsequent dephasing.

Conclusions:

• The proposed spectroscopic observable provides a direct experimental handle to quantify and monitor spatial quantum coherence in molecular systems.
• This method offers insights into the dynamics of excited states and their coherence evolution, relevant for energy transfer processes.