Coherent control of molecular dynamics in complex systems

The use of light to control the outcome of a reaction is one of the most exciting prospects in chemistry. Coherent control aims to steer a molecular system toward a desired outcome by exploiting quantum interference effects. Here we propose to develop adaptive femtosecond laser pulse shaping for coherent control of complex biological and synthetic biomimetic systems. In a closed-loop experiment combining molecular feedback, adaptive femtosecond pulse shaping, and a genetic learning algorithm, systems considered intractable on an ab initio quantum-mechanical level may be explored. This approach works on the Hamiltonian of the molecular system, iteratively refining the driving optical field to achieve a chosen target objective, i.e. enhancement of a specific reaction product pathway. We recently used this technique to demonstrate coherent control of a biological function. The applicability of this approach to biomolecules has opened new access for spectroscopic studies that will provide insight into how nature designs systems for optimal performance. We will explore the pathways, efficiencies, and underlying factors that govern ultrafast biological reaction dynamics in relation to their function, in studies of both native and model systems designed for energy and charge transfer. Of particular interest is the role of vibrational coherence in biological reaction dynamics and function. We will apply optimal control fields to prepare and manipulate vibrational wavepackets in relation to motions that enable or restrict pathways of energy or charge transfer reactions.