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Laser and conventional flash photolysis have been used to obtain the triplet—triplet absorption spectra, triplet lifetimes, rates of oxygen quenching and quantum efficiencies of triplet formation of protoporphyrin IX as the dication, monocation and free base in several solvent systems. The results are rationalised in terms of protoporphyrin IX existing as a monomer in organic or detergent solvents and as an aggregated species in aqueous environments.
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Sinclair et al. (1980) studied this question.
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