The non-adiabatic dynamics of trans-butadiene excited to its optically bright state has been simulated using ab initio multiple spawning (AIMS). Parallelizing the AIMS algorithm has allowed us to treat the electronic structure of this system on-the-fly with a high-level method capable of describing both static and dynamic electron correlation effects (multi-state complete active space second order perturbation theory [MS-CASPT2]), which are shown to be important for a balanced description of the electronic states of this system. We find that a large fraction of the non-adiabatic transitions to the ground state are preceded by twisting and pyramidalization motions in a single terminal ethylene unit. These motions are accompanied by charge transfer, which localizes an electron pair on one of the carbons of the twisted ethylene. By simulating time resolved photoelectron spectra we compare directly to experiment, where good agreement is seen thus supporting our mechanism. Furthermore we propose possible experimental signatures of the observed charge transfer character in butadiene.

Charge-transfer states in the nonadiabatic dynamics of photoexcited trans-butadiene

244th National Meeting (2012)

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