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Orientation and Energy Transfer in Chlorophyll Monolayers Diluted with Hexadecane. Fluorescence and Sensitized Fluorescence
Author(s) -
Gonen Oded,
Leva Haim,
Patterson L. K.
Publication year - 1981
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198100050
Subject(s) - chemistry , monolayer , hexadecane , fluorescence , photochemistry , molecule , excited state , aqueous solution , chlorophyll a , analytical chemistry (journal) , chlorophyll , luminescence , quantum yield , atomic physics , organic chemistry , optics , biochemistry , physics
The fluorescence and force‐area behavior of chlorophyll a (Chl a ) monomolecular films diluted with hydrocarbon on an aqueous subphase is reported. It is found that the diluent hexadecane, instead of conventional fatty alcohols, results in a substantial increase in the fluorescence yield of Chl a . The luminescence intensity varies nonmonotonically with respect to the intermólecular distance. A model for the mutual orientation of the chlorophyll pigments and the consequent energy transfer processes in terms of a Förster mechanism is proposed. For a random distribution of the Chl a molecules in the monolayer ( k 2 = 2/3) an average value of 43° is calculated for the angle between the molecular planes and the water surface. This model yields a value of 23 Å for the Förster R 0 . Also, a value of 58° is derived for the angle between the Q‐band transition moment and the line of intersection between the molecular plane and water surface. When a mixture of Chl a and Chl b in the monolayers is being excited at the absorption band of the latter pigment, typical fluorescence of Chl a is being detected. This sensitization process can also be interpreted in terms of the orientational model of the Chl molecules as presented in this work.