Structural Dynamics of Complex Molecules by Ultrafast Electron Diffraction : Concepts, Methodology and Applications

Citation

Srinivasan, Ramesh (2005) Structural Dynamics of Complex Molecules by Ultrafast Electron Diffraction : Concepts, Methodology and Applications. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/DTG2-5932. https://resolver.caltech.edu/CaltechETD:etd-05122005-083103

Abstract

The central theme in ultrafast electron diffraction (UED) is the elucidation of the structural dynamics of transient molecular entities. With properly timed sequences of ultrafast electron pulses, it is now possible to image complex molecular structures in the four dimensions of space and time with resolutions approaching 0.01 [angstroms] and 1 ps, respectively. Reaching this spatiotemporal resolution on the atomic scale has been the driving force behind the development and application of the third generation UED instrument–-the subject of this dissertation. The current state-of-the-art in resolutions and sensitivity, together with theoretical advances, has made possible the direct determination of transient structures, leading to studies of diverse molecular phenomena hitherto not accessible to other techniques. By freezing structures on the ultrafast timescale, we are able to develop concepts that correlate structure with dynamics. Examples include structure-driven radiationless processes, dynamics-driven reaction stereochemistry, and non-equilibrium structures exhibiting negative temperature, bifurcation, or selective energy localization in bonds. These successes in the studies of complex molecular systems, even without heavy atoms, establish UED as a powerful method for mapping out temporally changing molecular structures in chemistry, and potentially, in biology.

Thesis Files