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Direct observation and understanding of atomic-level structural dynamics are important frontiers in scientific research and applications. Femtosecond electron diffraction (FED), a technique that combines time-resolved pump-probe and electron diffraction concepts, holds a great promise to reveal the dynamical processes of ultrafast phenomena in biology, chemistry and solid-state physics at the atomic time and length scales. This thesis presents the development of a tabletop femtosecond electron diffractometer and its applications to study the ultrafast structural dynamics of thin metal films. Using a delicate instrument design and careful experimental configuration, sub-picosecond temporal and sub-milli-°angstr¨om spatial resolutions are maintained simultaneously in the diffractometer. Using this diffractometer, we have studied the dynamics of coherent and random thermal lattice motions initiated by femtosecond laser pulses in ultrathin metal films, and particularly, the mechanism of coherent acoustic phonon generation. We also introduce a new approach to measure the electronic Gr¨uneisen parameter in metals using FED at and above room temperature. Finally, we study the ultrafast demagnetization process in ferromagnetic transition metal Ni by monitoring the transient lattice dynamics with FED.
Coherent Phonon, Ultrafast Demagnetization, Femtosecond Electron Diffraction, Electronic Thermal Expansion
Date of Defense
June 12, 2008.
Submitted Note
A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Bibliography Note
Includes bibliographical references.
Advisory Committee
Jianming Cao, Professor Directing Dissertation; Sanford Safron, Outside Committee Member; Peng Xiong, Committee Member; Nicholas Bonesteel, Committee Member; Mark A. Riley, Committee Member.
Publisher
Florida State University
Identifier
FSU_migr_etd-2603
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