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MO: Fachverband Molekülphysik

MO 23: Femtosecond Spectroscopy VI

MO 23.6: Hauptvortrag

Donnerstag, 21. März 2013, 15:30–16:00, F 102

Noise-Induced Förster Resonant Energy Transfer between Orthogonal Dipoles in Photoexcited Molecules — •Peter Nalbach¹, Igor Pugliesi², Heinz Langhals³, and Michael Thorwart¹ — ¹I. Institut für Theoretische Physik, Universität Hamburg — ²II. Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München — ³Department of Chemistry, Ludwig-Maximilians-Universität München

Förster resonance energy transfer (FRET) has become a process of ubiquitous importance for proximity measurements of light absorbing and fluorescent structures. Recent experiments, however, in a perylene bisimide dyad, where donor and acceptor dipoles are perfectly orthogonal in equilibrium and, thus, FRET should vanish, show energy transfer with near unit quantum yield.

We show [1] that FRET in an orthogonally arranged donor-acceptor pair can be induced by environmental noise. Environmental fluctuations break the strict orthogonal dipole arrangement and cause effective fluctuating excitonic interactions. Using a scaling argument, we show that interaction fluctuations are coupled to those of the energy levels and are strong enough to induce large FRET rates. We discuss the temperature dependence and predict a modified distance dependence as compared to standard Förster theory. In summary, our findings show that the basic FRET theory has to be extended and we highlight the importance of environmental fluctuations for energy transfer processes.

[1] P. Nalbach, I. Pugliesi, H. Langhals, and M. Thorwart, Phys. Rev. Lett. 108, 218302 (2012).