Development of efficient light-harvesting technologies hinges on our understanding of the fundamental physics of light-harvesting in both natural and artificial systems. This work addresses the following topics, i.) the mechanism underlying the remarkably efficient electronic energy transfer in natural light harvesting antennas, ii.) a femtosecond time-resolved photonumeric technique to quantitatively characterize transient chemical species.
A non-adiabatic model for photosynthetic energy transfer in light harvesting antennas is proposed. Light harvesting antennas use a set of closely spaced pigment molecules held in a controlled relative geometry by a protein. It is shown that in the Fenna-Matthews-Olson (FMO) antenna protein, the antenna found in green sulfur bacteria, the excited state electronic energy gaps are resonant with a quantum of vibrational energy on its pigment, bacteriochlorophyll a. Through a dimer model loosely based on FMO, it is shown that such a resonance leads to an unavoidable nested non-adiabatic energy funnel on the excited states of photosynthetic antennas. The non-adiabatic model presented here leads to enhanced vibrational oscillations on the ground electronic state of these antennas, the 2D spectroscopic signatures and oscillation frequencies of which are consistent with all the reported 2D signatures of long-lived oscillations, including the ones that are not explained by prior models of excited state electronic energy transfer. Extensions that account for both resonant and near-resonant pigment vibrations suggest that photosynthetic energy transfer presents a novel design in which electronic energy transfer proceeds non-adiabatically through clusters of vibrations with frequencies distributed around electronic energy gaps.
The latter part of the thesis presents absolute measurements of femtosecond pump-probe signal strength. The experiments demonstrate quantitative time-resolved measurement of absolute number of excited state molecules. Based on these measurements, an all-optical technique that simultaneously determines concentration and extinction coefficient of an unknown sample is presented. Unlike prior such analytical techniques, the present photonumeric method does not require any sample isolation, physical handling or in situ calibrant. In principle, the experimental and theoretical framework developed allows extensions towards characterization of transient chemical species.
|Advisor:||Jonas, David M.|
|Commitee:||Cundiff, Steven T., Damrauer, Niels H., Eaves, Joel D., Parson, Robert P.|
|School:||University of Colorado at Boulder|
|School Location:||United States -- Colorado|
|Source:||DAI-B 75/09(E), Dissertation Abstracts International|
|Subjects:||Analytical chemistry, Physical chemistry|
|Keywords:||2 dimensional spectroscopy, Absolute pump-probe, Exciton, Forster resonance energy transfer, Photonumeric, Transient chemical species|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be