Dr. Brett Barwick
Physical Biology Center for Ultrafast Science & Technology
California Institute of Technology
Monday, February 1, 2010
4:30 p.m.
Cardwell 102
Imaging at the nm and fs scales with ultrafast electron microscopy (UEM)
Investigating ultrafast phenomena with femtosecond (10-15 s) and attosecond (10-18 s) temporal resolution is pivotal to understanding the dynamic processes that atomic, molecular and condensed matter systems undergo. The time scale for dynamics, at the atomic length scale, ranges from picoseconds to attoseconds for processes such as the heating of a thin metallic crystal and the motion of plasmons in metals. In this talk I will describe ultrafast imaging using “single-electron” packets as applied to several different nanoscale ultrafast processes. In particular, I will describe a new imaging method that exploits the fact that “free” electrons (when near a third body) can absorb and emit multiple photons. The physics describing the absorption and emission of photon quanta by free electrons is well known in AMO physics as a “free-free” transition and is manifested in the laser assisted photoemission effect. We form images by using only electrons that have absorbed photons; allowing us to observe the evanescent electric field created by plasmons that have been excited by an intense ultrafast optical pulse. In describing this imaging technique dubbed, photon-induced near-field electron microscopy (PINEM), I will also discuss future plans to extend the temporal resolution to tens of femtoseconds and possibly even the attosecond regime.
