Greg Engel

Tracking Ultrafast Dynamics and Transport at the Mesoscale: From Photosynthesis to Optical Resonance Imaging

Control of excited state dynamics at the nanometer to micron scale remains a grand challenge for material science, chemistry, and engineering.  Ultrafast spectroscopies to probe femtosecond dynamics, and we can use these signals to intuit excitonic transport from the spectral signals.  Recently, we have developed new multidimensional spectroscopies to show that the complex interplay between the chlorophyll molecules and their environment within the protein represents an entirely different approach to dictating energy transfer from what we create chemically in a beaker.  We are particularly interested in how the electronic excitation couples to local molecular vibrations and how these vibrations can steer electronic dynamics.  To gain more direct spatial information, we implemented chiral nonlinear spectroscopy to track wavefunction collapse after excitation to reveal how biology exploits dephasing to efficiently absorb light while systematically frustrating re-emission.  Finally, I will discuss ongoing work to create an Optical Resonance Imaging system (ORI) to permit visualization of femtosecond dynamics below the diffraction limit.  This approach will permit direct imaging of dynamics at the mesoscale.