TIME-RESOLVED DELAYED LUMINESCENCE OF CHLOROPHYLL-ALPHA IN ANHYDROUS POLYMER SYSTEMS

Absorption, fluorescence and time-resolved delayed luminescence spectr a of chlorophyll a in thin anhydrous polymer matrices of polyvinyl alc ohol and nitrocellulose have been measured. Delayed luninescence spect ra were measured in the microsecond time range in the 600-800 nm regio n at different temperatures (8-300 K). Delayed luminescence kinetics f or the following chlorophyll a species: monomeric form, chlorophyll-ch lorophyll dimer and chlorophyll-nitrocellulose complex, have been obta ined and decay times are evaluated (9-17 mu s). Decay times are found to be independent of temperature. The possible mechanisms responsible for delay luminescence are discussed. It is found that the delayed lum inescence intensity slowly and linearly increases with decreasing temp erature. Thermal repopulation of the singlet excited state of chloroph yll a from the triplet state together with annihilation processes have been excluded as mechanisms for generation delayed luminescence. Char ge separation and ion recombination are discussed as more likely mecha nisms of delayed luminescence. Delayed luminescence results are compar ed to those reported in the literature chlorophyll a under a variety o f conditions.