The resolution of electron-based imaging techniques can be increased with the development of ultra-short, ultra-cold electron beam generation techniques.
Short beams of electrons are used in imaging processes such as ultrafast electron diffraction and ultrafast electron microscopy to study the motions of atoms in materials. The use of ultracold and subpicosecond-length beams can improve the resolution of these techniques, but the researchers struggled to create beams with these two properties. The current situation has changed with a new approach developed by Tim de Raadt et al. of Eindhoven University of Technology in the Netherlands. According to the researchers, the method they developed will make it possible to visualize protein structures at the atomic level in a single shot.
The team's method involves creating a cloud of cold rubidium atoms in a magneto-optical trap where four laser beams intersect. Two more laser beams are used to excite and ionize these atoms. By releasing electrons at a temperature of about 20 K and accelerating them through a small hole in the trap wall, this process, called photoionization, creates electron beams. As the distance from the hole increases, these ultra-cold beams shorten in duration and almost disappear at the point of self-compression.
The properties of beams at the self-compression point were studied by De Raadt et al. They measured band lengths as short as 25 ps, compared to the previous best value of 0,735 ps. They argue that the photoionization time slot determines the minimum beam duration by comparing the observed temporal structure of the beams with simulations of the photoionization process. According to the researchers, a modified setup would enable electron beams with lower temperatures than those seen in this experiment, resulting in ultrafast diffraction and even better resolution for microscopy.
Source: https://physics.aps.org/articles/v16/s68
Günceleme: 21/05/2023 16:40