A multi-exponential analysis is made of the fall in the intensity of delayed fluorescence produced by nanosecond light pulses from a nitrogen laser between the 40th and 550th μsec from the moment of switching off the exciting radiation at room temperature. The multi-component character of the disappearance of fluorescence is due to the different paths of transition of the reaction centre of the pigment of the second photochemical system of photosynthesis from the oxidized to the reduced state. A description is given of a laser phosphoroscope with a time resolution of 20 μsec. Delayed fluorescence in intact samples is characterized by two components with lifetimes in the excited state of 30 and 150 μsec. Treatment of the preparations with 3(3,4-dichlorophenyl)-1, 1-dimethylurea (DCU) causes quenching but does not change the kinetic characteristics of fluorescence. Hydroxylamine (NH2OH) in low concentrations increases the intensity of fluorescence while high ones lead to quenching; the component with a lifetime 150 μsec disappears. The findings confirm the model according to which delayed fluorescence in the microsecond range is due to the presence in the system of heterogeneous centres.
|Number of pages||7|
|Publication status||Published - Dec 1 1980|
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