Ultrafast Two-Dimensional Spectroscopy of Photosynthetic Systems

This chapter starts with a review of the theoretical foundation for understanding two-dimensional electronic spectroscopy (2DES) signals in molecular systems. We derive and motivate key properties of 2DES, demonstrating its ability to yield complex information about energy transfer processes and couplings within molecular assemblies, such as photosynthetic antennae. We continue with a discussion encompassing crucial aspects of experimental implementations of 2DES, with particular attention to polarization-controlled experiments. Through illustrative applications of 2DES in studies of light-harvesting functions in isolated complexes and an intact photosyntetic unit in green sulfur bacteria the chapter reveals the extensive insights into the photophysical functions of photosynthetic machinery that can be obtained. Emphasis is placed on identifying exciton coupling, delineating energy transfer pathways, and quantifying rates and efficiencies. The chapter concludes by anticipating future 2DES developments, e.g., the studies on intact photosynthetic units at physiological temperatures, that will contribute to a more holistic comprehension of primary photosynthetic functions, particularly in light harvesting and charge separation.