Fluorescence lifetimes of pure chlorophyll a monolayers were determined by single-photon counting and by picosecond spectroscopy. Neither technique could resolve its very fast decay rate, attributed to a high aggregate concentration and rapid intermolecular energy transfer. The same experiments were performed on monolayers of chlorophyll a diluted with phospholipids at a molar ratio of 1 to 100. From the single-photon counting decay curves, two fluorescence lifetimes were deconvoluted, i.e. 4.9 and 2.3 ns, indicating the presence of monomeric and aggregated chlorophyll a, respectively. They differ somewhat from the picosecond spectroscopic result where only one lifetime at 3.3 ns was calculated. This is indicative of an exciton annihilation process since it is smaller than the average of the single-photon counting lifetimes. Fluorescence spectroscopy was also used to better understand the photophysics of the chlorophyll a monolayer.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry