Vivek Tiwari: Photosynthetic Excitons Coupled Through Resonant Vibrational-Electronic Coupling – To what extent do the reduced basis set descriptions work?

Ultrafast internal conversion between excited states of photosynthetic pigments has been a subject of intense spectroscopic interest owing to its near unity quantum yield. Of particular interest is the possibility of strong non-adiabatic mixing between vibrational and electronic degrees of freedom caused by resonances between exciton energy gaps and dense low-frequency vibrational spectrum of photosynthetic pigments. Coherent superpositions between vibronically mixed states have recently been reported in several photosynthetic proteins, and quantum dynamical simulations of vibronic exciton models have further suggested a possible functional role for excited state vibronic coherences in enhancing the rates of energy and charge delocalization. A key question which arises in this context is -- what are the distinguishing properties of excitons coupled through resonant vibronic coupling, and whether these properties could be well approximated in basis sets with reduced vibrational dimensionality without over-simplifying the expected excited state dynamics? The above question will be the main theme of this talk.