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Reverse Intersystem Crossing in Rose Bengal. II. Fluence Dependence of Fluorescence Following 532 nm Laser Excitation ¶
Author(s) -
Larkin John M.,
Donaldson William R.,
Knox Robert S.,
Foster Thomas H.
Publication year - 2002
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2002)0750221ricirb2.0.co2
Subject(s) - intersystem crossing , fluorescence , chemistry , rose bengal , quantum yield , triplet state , photochemistry , singlet state , atomic physics , physics , optics , excited state , molecule , organic chemistry
A fluence‐dependent fluorescence technique was used to observe reverse intersystem crossing from a certain higher‐lying triplet state of rose bengal populated by a single pulse of 532 nm light. The quantum yield of reverse intersystem crossing from this state was determined to be 0.12 ± 0.02 for rose bengal in phosphate‐buffered saline. The importance of including molecular rotation effects in the analysis of fluorescence resulting from reverse intersystem crossing is discussed. Differences in the photochemical reactivity of upper triplet states in biological systems have been previously hypothesized to result from photophysical differences, particularly substantial differences in their reverse intersystem crossing yields. In this work this hypothesis is analyzed quantitatively, using numerical models of the population dynamics. These models suggest that reverse intersystem crossing alone cannot adequately explain the differences in biological response.