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Structural dynamics by ultrafast electron crystallography

Citation

Chen, Songye (2007) Structural dynamics by ultrafast electron crystallography. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-01302007-102801

Abstract

Ultrafast electron crystallography (UEC), combining the ultrafast time resolution with femtosecond lasers and the atomic spacial resolution with electron crystallography, is developed and applied to elucidate the structural dynamics in solids, surfaces and macromolecular systems. The UEC experiments for surface studies were first demonstrated on semiconductor surfaces. Coherent nonthermal motions of atoms following ultrafast laser irradiation were shown with the timescales in picoseconds, and the amplitude of the motions was determined in picometer. Using Langmuir-Blodgett films, two-dimensional crystalline monolayer, bilayers and multilayers of fatty acids and phospholipids were also studied by UEC. The atomic structures under different preparation conditions were determined. The structural dynamics following a temperature jump induced by femtosecond laser on the substrates were obtained and compared to the equilibrium temperature dependence. It was observed that a coherent anisotropic expansion solely along the aliphatic chains happens at picosecond timescale, followed by nonequilibrium contraction and restructuring at longer times. The effects of different molecules, layer thickness and substrate on the dynamics were examined. Unlike monotonic disordering in the equilibrium heating, a transient structural ordering was revealed on the picosecond timescale.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:diffraction; fatty acid; Langmuir-Blodgett film; phospholipids; surfaces and interfaces
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Zewail, Ahmed H.
Thesis Committee:
  • Zewail, Ahmed H. (chair)
  • Scherer, Axel
  • Yeh, Nai-Chang
  • McKoy, Basil Vincent
Defense Date:30 November 2006
Author Email:songyech (AT) caltech.edu
Record Number:CaltechETD:etd-01302007-102801
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-01302007-102801
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:409
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:12 Feb 2007
Last Modified:26 Dec 2012 02:29

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