Mapping Atomic Motions with Ultrabright Electrons: Fundamental Space-Time Limits to Imaging Chemistry and Biological Processes

One of the dream experiments in science has been to watch atomic motions on the primary timescales of chemistry. This experiment has been referred to as "making the molecular movie" with respect to observing net rms atomic motions during structural changes. With the development of ultrabright electron capable of literally lighting up atomic motions, this experiment was first realized (Siwick et al Science 2003) and efforts accelerated with the onset of XFELs (Miller, Science 2014). We now are beginning to see the underlying physics for the generalized reaction mechanisms that have been empirically discovered over time. The “magic of chemistry” is this enormous reduction in dimensionality in the barrier crossing region that ultimately makes chemical concepts transferrable. New approaches based on the principles used for femtosecond electron diffraction, both in terms of source technology and image reconstruction, hold promise for real space studies of single biomolecules.