Ultrafast Structural Dynamics in Metals

• Other Authors: Nie, Shouhua, 1981- (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Physics
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-2603

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. === A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. === Summer Semester, 2008. === June 12, 2008. === Coherent Phonon, Ultrafast Demagnetization, Femtosecond Electron Diffraction, Electronic Thermal Expansion === Includes bibliographical references. === Jianming Cao, Professor Directing Dissertation; Sanford Safron, Outside Committee Member; Peng Xiong, Committee Member; Nicholas Bonesteel, Committee Member; Mark A. Riley, Committee Member.