Ultrafast excited state structural dynamics of carotenoids.

摘要

This dissertation describes the development and implementation of a visible/near infrared pump/mid-infrared probe apparatus.;Chapter 1 describes the background and motivation of investigating optically induced structural dynamics of carotenoids, paying specific attention to one and two photon excitation and vibrational spectroscopy.;Chapter 2 describes the alignment and optimization of the regenerative amplifier utilized for the research in Chapters 5 and 6.;Chapter 3 will discuss the investigation of DCM, a laser dye with a fluorescence signal resulting from a charge transfer state. By studying the dynamics of DCM and of its methyl deuterated isotopomer (an otherwise identical molecule), we are able to investigate the origins of the charge transfer state and provide evidence that it is of the controversial twisted intramolecular (TICT) type.;Chapter 4 presents an investigation of the excited state dynamics of peridinin, the carotenoid responsible for the light harvesting of dinoflagellates. This investigation allows for a more detailed understanding of the importance of structural dynamics of carotenoids in light harvesting.;Chapter 5 introduces the use of two-photon excitation to the S1 state, combined with one-photon excitation to the S2 state of the carotenoid beta-apo-8'-carotenal. These investigations show evidence for the formation of solitons, previously unobserved in molecular systems and found in conducting polymers.;Chapter 6 presents further proof of the conclusion of Chapter 5 that method of excitation affects the final ground state position due to a complicated S1 state potential energy surface in many carotenoids.