Two-Dimensional Electronic Spectroscopy Reveals the Spectral Dynamics of Förster Resonance Energy Transfer

Abstract

Two-dimensional electronic spectroscopy (2D ES) probes the energies of chromophores and their coupling, and therefore the technique is now widely used for studying excitation energy-transfer mechanisms. The ubiquity and importance ofFörster Resonance Energy Transfer (FRET) demand a thorough study of its signatures in 2D ES. Here, using principles from noisy-light spectroscopy to account for the spontaneous transfer event, we describe a model that explicitly includes the intramolecular vibrational modes necessary to activate FRET. Our laboratory measurements of carbocyanine dyes are consistent with three theoretical results regarding the location, shape, and spectral dynamics of the energy-transfer peak. The signatures derived from the vibronic FRET model serve as a benchmark for ongoing work on energy-transfer mechanisms.