Isolating Pure Donor and Acceptor Signals by Polarization-Controlled Transient Absorption Spectroscopy

The optical spectra of moleculesare often highly congested, inhibitingdefinite assignment of features and dynamics. In this work, we demonstrateand apply a polarization-based strategy for the decomposition of time-resolvedoptical spectra to analyze the electronic structure and energy transferin a molecular donor-acceptor (D-A) dyad. We choosea dyad with orthogonal transition dipole moments for D and A and highfluorescence quantum yield to show that polarization-controlled ultrafasttransient absorption spectra can isolate the pure D and A parts ofthe total signal. This provides a strategy to greatly reduce spectralcongestion in complex systems and thus allows for detailed studiesof electronic structure and electronic energy transfer.