Physics Colloquium, Dwayne Miller

Femtosecond Electron Diffraction: Atomic Level Movies

Dwayne Miller

University of Toronto

The picosecond barrier to high brightness electron pulses has been broken. Femtosecond Electron Diffraction harbours great potential for providing atomic resolution to structural changes as they occur, essentially watching atoms move in real time --- directly observe transition states. This experiment has been referred to as "making the molecular movie" and has been previously discussed in the context of a gedanken experiment. With the recent development of femtosecond electron pulses with sufficient number density to execute nearly single shot structure determinations, this experiment has been finally realized. A new concept in electron wavepacket generation was developed based on an exact solution to the N-body electron progation problem involving up to 10,000 interacting electrons. This study derived the conditions for a new generation of extremely bright electron pulsed sources for molecular imaging. This development represents a significant advance that has taken a gedanken experiment to reality. It is now possible to atomically resolve transition state processes. In this context, an atomic level view of melting has been obtained under strongly driven conditions for Al in which the process can be described within a thermally accessed barrier crossing. Subsequent studies of Au have helped further ellucidate the mechanism for the melt zone propagation. In addition to this line of study, applications to specific molecular systems will be discussed in the context of directly imaging reaction dynamics.

3.30 p.m., Smith Laboratory, Room 1005

Refreshments served in Smith 1094 at 3:00 p.m.