The Next-Generation Camera for Molecular Movies

Electron beam technology has come a long way since German electrical engineer Ernst Ruska invented the electron microscope in 1931. Today, pulsed electron beams of extremely short durations are used to light up loci and trajectories of atoms and molecules for determining structure-function relationships in a variety of materials under ultrafast electron diffraction microscopy.

Siddiqui et al. expanded the pallet of measurable systems by developing a new, advanced electron source. Their High Repetition-rate Electron Scattering apparatus, or HiRES, can deliver high flux, high brightness, relativistic electron pulses at very high repetition rates.

“Relativistic electron pulses are typically produced by low duty-cycle, radio frequency accelerators, which at best can deliver a few hundred shots per second due to prohibitive heat loads. This limits their scope for demanding experiments that require high average flux,” said author Daniele Filippetto. “HiRES, on the other hand, is based on a new concept of electron gun design, which overcomes current limitations and enables much higher frequency operation.”

Indeed, in addition to standard “pump-probe” experiments, the researchers demonstrated novel capabilities for ultrafast electron diffraction, from nanoscale diffraction via extreme beam shrinking to the recording of high signal-to-noise ratio (SNR) gas phase patterns in seconds instead of minutes.

“The radical reduction in acquisition times with proportional SNR gains will be a game-changer for gas/liquid phase ultrafast electron diffraction studies,” said Filippetto. “The next big milestone for HiRES is to get below 100 femtoseconds, enabling direct access to the fastest photochemical changes, which would help unleash the full potential of HiRES as the next generation camera for molecular movies.”

Source: “Relativistic ultrafast electron diffraction at high repetition rates,” by K. M. Siddiqui, D. B. Durham, F. Cropp, F. Ji, S. Paiagua, C. Ophus, N. C. Andresen, L. Jin, J. Wu, S. Wang, X. Zhang, W. You, M. Murnane, M. Centurion, X. Wang, D. S. Slaughter, R. A. Kaindl, P. Musumeci, A. M. Minor, and D. Filippetto, Structural Dynamics (2023). The article can be accessed at http://doi.org/10.1063/4.0000203 .

This paper is part of the Enabling Methods in Ultrafast Electron Diffraction, Scattering and Imaging Collection, learn more here .