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Abstract— The fluorescence decay kinetics of photosynthetic mutants of Chlamydomonas reinhardii which lack photosystem II (PS II), photosystem I (PS I), and both PS II and PS I have been measured. The PS II mutant strain8–36C exhibits fluorescence decay lifetime components of 53, 424 and 2197 ps. The fluorescence decay of a PS I mutant strain12–7 contains two major fluorescence decay components with lifetimes of 152 and 424 ps. The fluorescence decay of mutant strain C2, which lacks both PS II and PS I, is nearly single exponential with a lifetime of 2561 ± 222 ps. In simulations in which it is assumed that wild‐type decays are a simple sum of the major decay components of the isolated parts of the photosynthetic unit as measured in the mutants, curves are obtained that fit the wild‐type C. reinhardii fluorescence decay data when the absorption cross‐sections of PS II and PS I are weighted approximately equally. The 89 ps lifetime component in the wild‐type is an average of 53 and 152 ps components arising from excitation transfer to and trapping in PS I and PS II. The single step transfer time in PS I is estimated to be between 100 and 700 fs depending on assumptions about array size. We find that between two and four visits to the PS I reaction center are required before final trapping.

Supporting InformationReagents. The organic azides were synthesized as reported in the literature and typical procedures are mentioned briefly below. Triphenyl phosphine, p-Nitroaniline and disperse orange 3 (all from Aldrich) were used without any further purification.Caution: Aromatic azides are usually stable compounds under reaction conditions. But all necessary precautions including use of safety glasses, gloves and handling/performing experiments in shatter-proof fume hoods should be followed. Syntheses. Preparation of 1-Azido-4-nitrobenzene.To a cooled suspension (0 °C) of the 4-Nitro-phenylamine (5g, 36mmol) in water (40 mL) was added concentrated HCl ( 35mL). To this mixture a solution of sodium nitrite (3.08, 47mmol) in water (15 mL) was added dropwise at -10 °C. The reaction mixture was stirred for 2 h. The red colored solution was filtered and cooled to 0 °C. Sodium azide (3.14 g, 47 mmol) in water (15 mL) was added slowly. The organic azide was separated out as a bright yellow solid with