Colloquium - David Beratan (Duke) - Light Harvesting and Delivery at the Molecular Scale: Oscillator Strength Focusing and Dexter Coupling Pathways

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David Beratan
November 17, 2015
4:00PM - 5:00PM
Location
1080 Physics Research Building - Smith Seminar Room - reception at 3:45pm in the Atrium

Date Range
Add to Calendar 2015-11-17 16:00:00 2015-11-17 17:00:00 Colloquium - David Beratan (Duke) - Light Harvesting and Delivery at the Molecular Scale: Oscillator Strength Focusing and Dexter Coupling Pathways

Among the intrinsic physical constraints facing artificial photosynthesis are (1) the propensity for absorbing a photon and (2) the kinetics for delivering the electronic excitation energy to a reaction center.  My seminar focuses on understanding the underpinning constraints on light absorption by molecular species and on triplet energy transport kinetics through molecules.  We have established a theoretical framework to define and to assess molecular contributions to Dexter (exchange) coupling pathways for triplet energy transfer, allowing us to determine the significance of the charge-transfer (CT) mechanism proposed by Closs, Scholes and others.  The CT mechanism is viable at short distances but is  swamped by an explosion in the number of virtual bridge exciton pathways at moderate to longer distances.  We have also explored the distribution of oscillator strengths in molecules to understand why only a few percent of the integrated oscillator strength guaranteed by the Thomas-Reiche-Kuhn sum rule is available for solar energy harvesting.

1080 Physics Research Building - Smith Seminar Room - reception at 3:45pm in the Atrium Department of Physics physics@osu.edu America/New_York public
Description

Among the intrinsic physical constraints facing artificial photosynthesis are (1) the propensity for absorbing a photon and (2) the kinetics for delivering the electronic excitation energy to a reaction center.  My seminar focuses on understanding the underpinning constraints on light absorption by molecular species and on triplet energy transport kinetics through molecules.  We have established a theoretical framework to define and to assess molecular contributions to Dexter (exchange) coupling pathways for triplet energy transfer, allowing us to determine the significance of the charge-transfer (CT) mechanism proposed by Closs, Scholes and others.  The CT mechanism is viable at short distances but is  swamped by an explosion in the number of virtual bridge exciton pathways at moderate to longer distances.  We have also explored the distribution of oscillator strengths in molecules to understand why only a few percent of the integrated oscillator strength guaranteed by the Thomas-Reiche-Kuhn sum rule is available for solar energy harvesting.