HIGH TIME RESOLUTION ELECTRON-PARAMAGNETIC-RESONANCE OF LIGHT-INDUCEDRADICAL PAIRS IN PHOTOSYNTHETIC BACTERIAL REACTION CENTERS - OBSERVATION OF QUANTUM BEATS

Light-induced radical pairs in fully deuterated photosynthetic reactio n centers of purple bacteria Rhodobacter sphaeroides have been studied by high time resolution electron paramagnetic resonance. Quantum beat oscillations are detected at early times after laser excitation for n ative and iron-removed reaction center preparations. Due to their spin -correlated generation, the secondary radical pairs P+[QFe(2+)](-) and P(+)Q(-) are expected to start out in a coherent superposition of eig enstates, as observed experimentally. Analysis of the quantum beats as a function of the static magnetic field can ultimately provide detail ed information on the molecular structure of the short-lived intermedi ates in the primary steps of bacterial photosynthesis.