FLUORESCENCE OF AGGREGATED FORMS OF CHL A IN VARIOUS MEDIA

The fluorescence lifetimes in the picosecond time range of various aggregated forms of chlorophyll a (Chi a) in different media (wet n-hexane, adsorbed layers and polymer films) were measured. Photographs of Chl a and Chl b poly(vinyl alcohol) (PVA) samples containing pigment oligomers are compared and discussed on the basis of previous and present spectral data concerning chlorophyll aggregation. In the investigated samples, the aggregated forms of Chl a can be divided into three groups: ''dry monomer'' (isolated from interaction with water), hydrated dimers and oligomers built from such dimers. These three forms have different emission lifetimes and, from photoacoustic spectra, yields of thermal deactivation. The excitation energy transfer from dry monomers to aggregated forms is rather ineffective.