Abstract
Weintroduce fluorescence-detected pump-probe microscopyby combining a wavelength-tunable ultrafast laser with a confocalscanning fluorescence microscope, enabling access to the femtosecondtime scale on the micrometer spatial scale. In addition, we obtainspectral information from Fourier transformation over excitation pulse-pairtime delays.
We demonstrate this new approach on a model system ofa terrylene bisimide (TBI) dye embedded in a PMMA matrix and acquirethe linear excitation spectrum as well as time-dependent pump-probespectra simultaneously. We then push the technique toward single TBImolecules and analyze the statistical distribution of their excitationspectra.
Furthermore, we demonstrate the ultrafast transient evolutionof several individual molecules, highlighting their different behaviorin contrast to the ensemble due to their individual local environment.By correlating the linear and nonlinear spectra, we assess the effectof the molecular environment on the excited-state energy.