Ultrafast single-molecule photonics: Excited state dynamics in coherently coupled complexes

We present a single-molecule study on femtosecond dynamics in multichromophoric systems, combining fs pump–probe, emission-spectra and fluorescence-lifetime analysis. The ultrafast fs approach gives direct information on the initial exciton dynamics after excitation. The lifetime data show superradiance, a direct measure for the extent of the coherent coupling and static disorder. The spectra finally reveal the role of exciton–phonon coupling. At the single-molecule level a wide range of exciton delocalization lengths and energy redistribution times is revealed.