Quantum Beats as Probes of the Primary Events in Bacterial Photosynthesis

Abstract

Light-induced radical pairs in fully deuterated iron-containing bacterial reaction centers of Rhodobacter sphaeroides have been studied by transient EPR following pulsed laser excitation. Quantum beat oscillations are observed in the transverse magnetization at low temperatures. Due to its spin-correlated generation, the secondary radical pair P+ [QA Fe2+]- is expected to start out in a coherent superposition of eigenstates, as observed experimentally. Thorough investigation of light-induced nuclear coherences, detected in the transverse electron magnetization, can provide detailed information on the electronic structure of the primary donor, which is essential for a better understanding of the primary events of bacterial photosynthesis.