Shirin Faraji: Excited-state processes and quantum effects in complex environments

Light-triggered processes, which are ubiquitous in nature and technology, are inherently quantum. Phenomena such as photovoltaic effect, charge migration, and proton-coupled electron transfer require quantum mechanical description. Understanding and optimizing these processes is the key to novel technologies: bio-photovoltaics, optogenetics, photoelectrochemical cells, and clean energy devices. Mechanistic studies of these phenomena have motived the development of sophisticated time-resolved spectroscopies for real-time observation of photo-induced processes. Theoretical modeling is crucial for the interpretation of these experiments. By simulating excited-state dynamics and modeling relevant spectra, computer simulations can help to translate experimental observations into atomic-level mechanistic picture, providing detailed insight into the photochemical reactions. Theoretical modeling can also facilitate the computer-aided design of new biomolecules and novel materials with customized properties matching specific applications. The theoretical description of the excited electronic states in complex systems is one of the biggest challenges of theoretical chemistry. I will present two examples of light-induced processes in biological systems: photo-induced energy and electron transfer in DNA photo-damage repair by photolyases and competing excited-state processes in far-red fluorescent proteins. I will highlight the role of theory in developing mechanistic understanding of these important systems and outline the theoretical approaches used for this task with a particular emphasis on fundamental challenges in the field.