Femtosecond mega-electron-volt electron microdiffraction

TL;DR

This paper demonstrates a novel femtosecond mega-electron-volt electron microdiffraction technique with 5 μm spatial and 100 fs temporal resolution, enabling detailed study of ultrafast structural dynamics in materials.

Contribution

The authors experimentally demonstrate time-resolved mega-electron-volt electron microdiffraction with high spatial and temporal resolution, advancing ultrafast structural analysis capabilities.

Findings

Achieved 5 μm spatial resolution and 100 fs temporal resolution.

Obtained high-quality diffraction from a 10 μm paraffin crystal.

Time-resolved observation of phonon softening in polycrystalline bismuth.

Abstract

Instruments to visualize transient structural changes of inhomogeneous materials on the nanometer scale with atomic spatial and temporal resolution are demanded to advance materials science, bioscience, and fusion sciences. One such technique is femtosecond electron microdiffraction, in which a short pulse of electrons with femtosecond-scale duration is focused into a micron-scale spot and used to obtain diffraction images to resolve ultrafast structural dynamics over localized crystalline domain. In this letter, we report the experimental demonstration of time-resolved mega-electron-volt electron microdiffraction which achieves a 5 {\mu}m root-mean-square (rms) beam size on the sample and a 100 fs rms temporal resolution. Using pulses of 10k electrons at 4.2 MeV energy with a normalized emittance 3 nm-rad, we obtained high quality diffraction from a single 10 {\mu}m paraffin (C_44 H_90) crystal. The phonon softening mode in optical-pumped polycrystalline Bi was also time-resolved, demonstrating the temporal resolution limits of our instrument design. This new characterization capability will open many research opportunities in material and biological sciences.