Abstract: The primary reaction kinetics of the photosystem Ⅱ particles isolated from spinach (Spinacia oleracea Mill. ) have been studied using the subpicosecond transient absorption technique. Three lifetime components, (0.76±0.50) ps, (8.70±2.00) ps and (138.00±20.00) ps, were obtained by the multi-exponential curval fitting. When the samples were exposed to strong light for one hour, only one component, 133 ps, was found. It was proposed that the 760 fs component was most probably attributed to the energy transfer from light-harvesting system to the reaction center.

Key words: Photosystem Ⅱ, Light-harvesting system, Energy transfer, Time-resolved absorption spectroscopy