Ultrafast Electron Scattering: Femtosecond Electron Pulses in Materials Research

Combining ultrafast lasers and electron microscopes in novel ways makes it possible to directly ‘watch’ the time-evolving structure of condensed matter on the fastest timescales open to atomic motion. By combining such measurements with complementary (and more conventional) spectroscopic probes one can develop structure-property relationships for materials under even very far from equilibrium conditions and explore how light can be used to control material properties. Several examples of the remarkable new kinds of information that can be gleaned from ultrafast electron scattering will be given. For example, it is possible to make ‘molecular movies’ of atomic-level structural dynamics. It is also possible to directly probe the strength of the coupling between electrons and phonons in materials across the entire Brillouin zone and to probe nonequilibrium phonon dynamics (or relaxation) in exquisite detail. Femtosecond electron pulses are having broad impacts in materials research.