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Development of Femtosecond Electron Diffraction for Direct Measurements of Ultrafast Atomic Motions

Title: The Development of Femtosecond Electron Diffraction for Direct Measurements of Ultrafast Atomic Motions.
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Name(s): Park, Hyuk, author
Cao, Jianming, professor directing dissertation
Safron, Sanford A., outside committee member
Bonesteel, Nicholas, committee member
Piekarewicz, Jorge, committee member
Xiong, Peng, committee member
Department of Physics, degree granting department
Florida State University, degree granting institution
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2006
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: The evolution of material structures is governed by the making and breaking of chemical bonds and the rearrangement of atoms, which occurs on the time scale of an atomic vibrational period, hundreds of femtoseconds. Atomic motion on this time scale ultimately determines the course of phase transitions in solids, the kinetic pathways of chemical reactions, and even the function of biological processes. Direct observation and understanding these ultrafast structural dynamics at the time and length scales of atomic motions represent an important frontier in scientific research and applications. We have developed a femtosecond electron diffraction system (FED) capable of directly measuring the atomic motions in sub-picosecond temporal resolution and sub-milli-angstrom spatial resolution. In the path of the development of FED various technical challenges have been overcome and an unprecedented capability has been achieved. These advancements allow us to study a range of ultrafast structural dynamics directly on the fundamental level of atomic motions for the first time. With FED we measured laser-induced ultrafast structural dynamics in a 20-nm Al film by taking real-time snapshots of transmission electron patterns. The damped single-mode breathing motion of the Al film along the surface normal was recorded as coherent and in-phase oscillations of all the Bragg peak positions. The concurrent lattice heating was measured by tracking the associated Bragg peak intensity attenuation. This acoustic phonon can be well fitted with a classical harmonic oscillator model using a driving force which includes both electronic and lattice contribution. The pressure of the free electrons contributes significantly in driving the coherent acoustic phonons under nonequilibrium conditions when electrons and phonons are not thermalized. In addition, by using a pair of optical excitation pulses and varying their time delay and relative pulse intensities, we demonstrated successful control of coherent lattice motions.
Identifier: FSU_migr_etd-2265 (IID)
Submitted Note: A Dissertation Submitted to the Department of Physics in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy.
Degree Awarded: Spring Semester, 2006.
Date of Defense: December 7, 2005.
Keywords: Femtosecond Electron Diffraction, Time-Resolved Diffraction, Ultrafast Structural Dynamics, Femtochemistry
Bibliography Note: Includes bibliographical references.
Advisory Committee: Jianming Cao, Professor Directing Dissertation; Sanford A. Safron, Outside Committee Member; Nicholas Bonesteel, Committee Member; Jorge Piekarewicz, Committee Member; Peng Xiong, Committee Member.
Subject(s): Physics
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_migr_etd-2265
Owner Institution: FSU

Choose the citation style.
Park, H. (2006). The Development of Femtosecond Electron Diffraction for Direct Measurements of Ultrafast Atomic Motions. Retrieved from http://purl.flvc.org/fsu/fd/FSU_migr_etd-2265