Fluorescence decay measurements using a mode-locked argon laser and single photon time-correlated detection, help us understand energy migration in photosynthesis. For intact spinach chloroplasts we find multiple exponential decays. There is some hint of a very fast component (<100 ps), but our data reveal little about it. We would expect this to be due to "photosystem I units." In addition we find two components at longer times, both of which lengthen as conditions are changed from "open" reaction centers (0.1 and 0.7 ns) to "closed" reac-tion centers (1 and 2 ns). This may reflect two kinds of organization for "photosystem II units."
Sylvia J. Berens,
Warren L. Butler,
"Picosecond Fluorescence In Spinach Chloroplasts", Proc. SPIE 0322, Picosecond Lasers and Applications, (23 April 1982); doi: 10.1117/12.933210; https://doi.org/10.1117/12.933210