The use of picosecond time-resolved spectroscopic techniques to probe reaction dynamics provides valuable information about the initial steps of photochemical reactions. For accurate interpretation of data collected by means of these methods, it is imperative that the inherent limitations of the picosecond absorption and emission spectrometers are considered. Results obtained via picosecond spectroscopic methods are presented which increase our understanding of the photochemistry and photophysics of three classes of molecular systems. / From our investigations of a series of halosubstituted fluorenes in cyclohexane, it is shown that bond homolysis and intersystem crossing to the triplet manifold occur on a rapid ($<$20-40 ps) and competitive time scale in 9-halofluorenes. It is demonstrated through a discussion of possible dissociation modes which are consistent with the experimental data that photodissociation is best described as occurring exclusively from the excited singlet state, and that no dissociation pathways originating from the lowest excited triplet state are operative. / The results of transient absorption measurements on a series of substituted diphenylhexatrienes support assignments of the observed bands which are contradictory to previous reports. A critical discussion of the earlier interpretations based on instrumental artifacts and limitations is provided. The results of the effect of changing solvent polarizability, solvent polarity, substituents, and temperature are described and support the present assignments. The observed trends in the decay kinetics of the absorption bands with changing solvent and substituents are consistent with theoretical expectations. / The synthesis and spectroscopic characterization of a series of proton-transfer fluorophores derived from 3-hydroxyflavone are described. This investigation has led to the conclusion that these types of structural changes permit the tuning of the spectroscopic behavior of these dyes only within a narrow window, and that the classical tradeoffs expected between quantum efficiency, fluorescence lifetime, and extinction coefficient are observed. Assessment of the usefulness of the twenty-two compounds studied as secondary fluors in scintillating plastics leads to the identification four promising candidates. Positive factors in the assessment are a high extinction coefficient, high quantum yield for proton-transfer emission, and short proton-transfer fluorescence lifetime as compared to 3-hydroxyflavone. / Source: Dissertation Abstracts International, Volume: 56-11, Section: B, page: 6081. / Major Professor: Edwin F. Hilinski. / Thesis (Ph.D.)--The Florida State University, 1995.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77607 |
| Contributors | McGowan, William Michael., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 157 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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