Professor Jessica M. Anna


Department Seminar
Professor Jessica M. Anna
Department of Chemistry
University of Pennsylvania
Host: Professor Aaron Massari


Ultrafast Dynamics of Natural Light Harvesting Complexes and Model Systems

Photosynthetic organisms have developed the molecular level machinery to efficiently and effectively harvest solar energy. To accomplish this, they use natural multichromophoric assemblies called light harvesting complexes to absorb a photon and transfer the excitation energy to a reaction center where charge separation takes place with a high quantum efficiency. Elucidating the mechanism of energy transfer and electron transfer in these complexes is essential to (1) understanding their high quantum efficiencies and subsequently (2) incorporating this information into design principles for artificial photosynthetic systems, photocatalysts, and organic photovoltaic materials. However, despite much experimental and theoretical effort, there are still unanswered questions regarding energy and electron transfer in natural light harvesting complexes, and multichromophoric assemblies in general. 

In this talk, I will discuss our recent studies in this area where we apply ultrafast pump-probe and multidimensional spectroscopies in the visible and mid-IR spectral regions to the natural light harvesting complex, photosystem I (PSI), and structurally simpler model systems that mimic specific properties of light harvesting complexes, including artificial light harvesting chromophores, isolated cofactors, and host-guest complexes. From our studies, we gain insight into pathways of energy equilibration among different electronic states, information on solvation dynamics, and insight into how non-covalent interactions act to alter the properties and dynamics of cofactors. 


Professor Anna's group uses ultrafast nonlinear spectroscopy to understand photoinitiated processes and dynamics. In order to explore these processes we employ multidimensional spectroscopic methods in both the visible and infrared spectral regions. The major benefit of employing multidimensional spectroscopic techniques is that the resulting spectrum is a frequency-frequency correlation map where each excitation frequency is correlated to each detection frequency. This enables for direct information on couplings, mechanistic pathways and system-bath interactions to be obtained.

Departmental Seminar
Start date
Tuesday, Dec. 1, 2020, 9:45 a.m.
End date
Tuesday, Dec. 1, 2020, 11 a.m.