Journal article
Sensitized Triplet Formation of Chlorophyll-A and beta-Carotene
The naphthalene-sensitized formation of triplet excited chlorophyll-a (Chl-a) and all-transß-carotene has been studied by pulse radiolysis. The rate constants for transfer of triplet energy from naphthalene to Chl-a and all-transß-carotene in benzene at 25°C are (3.6 ± 0.6)·109M-1 s-1 and (10.7 ± 1.2)·109M-1 s-1, respectively.
The decays of the excited triplet states of naphthalene, Chl-a and all-transß-carotene all follow a mixed first-and second-order mechanism. The first-order rate constant for triplet decay is strongly dose dependent for naphthalene but only slightly dependent and independent of dose for Chl-a and all-transß-carotene, respectively.
The rate constants for triplet-triplet annihilation are (1.4 ± 0.3)·109M-1 s-1 for Chl-a and (3.6 ± 0.4)·109M-1 s-1 for all-transß carotene. The nearly constant ratio k(ß-carotene)/k(Chl-a) for the bimolecular triplet energy transfer rate constants is discussed in terms of the molecular shapes of the two molecules.
The energetics of the triplet-triplet annihilation of all-transß-carotene are discussed, and it is proposed that production of the excited 1AB state may be a major route in the annihilation process.
Language: | English |
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Year: | 1980 |
Pages: | 719-725 |
ISSN: | 17511097 and 00318655 |
Types: | Journal article |
DOI: | 10.1111/j.1751-1097.1980.tb04048.x |