Broadband 2D Electronic Spectroscopy Reveals a Carotenoid Dark State in Purple Bacteria

Abstract

A Light in the Dark Carotenoids enhance the efficiency of photosynthesis by absorbing light at wavelengths inaccessible to chlorophyll. However, the mechanism underlying transfer of the absorbed energy from these pigments to the site of chemical catalysis is unclear. Studies have debated the involvement of a “dark” state in the carotenoid electronic structure—a state inaccessible by direct absorption populated by partial relaxation of the initial excited state. Ostroumov et al. (p. 52 ) used two-dimensional electronic spectroscopy to provide evidence of this state.