Delayed fluorescence as a probe of radiationless transitions in anthracene and algae
Stacy, William Turlay
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https://hdl.handle.net/2142/25841
Description
Title
Delayed fluorescence as a probe of radiationless transitions in anthracene and algae
Author(s)
Stacy, William Turlay
Issue Date
1970
Doctoral Committee Chair(s)
Brown, Frederick C.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
delayed fluorescence
radiationless transitions
anthracene
algae
chlorophyll
Language
en
Abstract
The delayed fluorescence emitted by both crystalline anthracene
and chlorophyll a in algae is studied. In the case of crystalline
anthracene, the blue light-excited delayed fluorescence is used to study
the temperature dependence of monomolecular intersystem crossing. The
associated rate constant k is found to obey an equation of the form
[equation] where E = 900 ± 100 cm and k2/k1 = 800 + 200. A calculation of the
relevant Franck-Condon factors using the method developed by Siebrand
yields good agreement with the experimental value of k2/k1 . At temperatures
below 90 o K, the temperature dependence of the delayed fluorescence
intensity exhibits a pronounced maximum which is qualitatively explained
in terms of triplet exciton traps.
The delayed fluorescence emitted by algae is explained in terms of
a triplet exciton fusion model in which the production of triplets is
mediated by a photochemical reaction center (photosystem II). The evidence
for this model is based on an extensive study of the time dependence of
the luminescence decay and the observation that, at low light levels,
the delayed fluorescence' intensity is proportional to the square of the
excitation intensity. Direct proof in the form of a magnetic field effect
on the delayed fluorescence was not obtained.
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