Mohammed Hassan, associate professor of physics and optical sciences, led a group of researchers to develop the first transmission electron microscope powerful enough to take images of electrons in motion. Photo by Ame Henning
Imagine having a camera powerful enough to capture still images of moving electrons. Electrons are traveling so fast they could circle the Earth multiple times in a matter of seconds. Researchers at the University of Arizona have developed the world's fastest electron microscope, which can do just that.
They believe their research will lead to breakthroughs in fields such as physics, chemistry, bioengineering and materials science.
“When you buy the newest smartphones, they have better cameras,” said Mohammed Hassan, an associate professor of physics and optical sciences.
“This transmission electron microscope is like the incredibly powerful camera in your latest smartphone. It can take pictures of previously invisible things, like electrons. We hope that this microscope will help the scientific community understand the quantum physics behind the behaviour and movement of electrons.”
Hassan led a team of researchers from the Department of Physics and Optical Sciences who published the research paper, “Attosecond Electron Microscopy and Diffraction,” in the journal Science Advances.
Hassan conducted the research with Nikolai Golubev, assistant professor of physics; co-first author Dandan Hui, a former optics and physics researcher now at the Xi'an Institute of Optics and Fine Mechanics, Chinese Academy of Sciences; co-first author Hussein Al-Qattan, a University of Alberta graduate and assistant professor of physics at Kuwait University; and Mohammed Senaly, a graduate student studying optics and physics.
A transmission electron microscope is a tool used by scientists and researchers to magnify objects up to millions of times their actual size in order to observe details too tiny to detect with traditional light microscopes.
Instead of using visible light, a transmission electron microscope shines a beam of electrons onto the sample being studied. The interaction of the electrons with the sample is captured by a lens and detected by a camera sensor to produce a detailed image of the sample.
These principles are exploited in ultrafast electron microscopes, which were first developed in the 2000s and use a laser to generate a pulsed beam of electrons. This technique dramatically improves the microscope's time resolution – its ability to measure and observe changes in a sample over time.
In these ultrafast microscopes, image quality is not determined by the camera shutter speed, but rather the resolution of a transmission electron microscope is determined by the duration of the electron pulse.
The faster the pulse, the better the image.
Ultrafast electron microscopes have previously worked by firing off trains of electron pulses at speeds of a few attoseconds – an attosecond is one hundred trillionth of a second. Pulses this fast create a series of images, like frames in a movie, but scientists have still missed the reactions and changes in electrons that occur between these frames as they evolve in real time.
To freeze and observe electrons in place, University of Alberta researchers have, for the first time, generated single attosecond electron pulses as fast as the electrons are traveling, thereby increasing the time resolution of the microscope — like a high-speed camera that captures movements that are normally invisible to the naked eye.
Hassan and his colleagues build on the Nobel Prize-winning work of Pierre Agostini, Ferenc Krauss and Anne Lhuillier, who were awarded the Nobel Prize in Physics in 2023 for being the first to generate pulses of extreme ultraviolet light short enough to be measured in attoseconds.
Building on that work, researchers at the University of Alberta have developed a microscope that splits a powerful laser into two parts: a very fast pulse of electrons and two ultrashort pulses of light. The first pulse of light, called the pump pulse, delivers energy to the sample, causing electrons to move and other rapid changes to occur.
The second light pulse, also known as the “optical gating pulse,” acts like a gate by creating a short time window during which a single, gated attosecond electron pulse is produced. The speed of the gating pulse therefore determines the resolution of the image. By carefully synchronizing the two pulses, researchers can control when the electron pulse probes the sample, allowing them to observe ultrafast processes at the atomic level.
“Improvements to time resolution in electron microscopes have been anticipated for a long time and are of interest to many research groups, because we all want to see electrons moving,” Hassan said.
“These movements happen in attoseconds. But now, for the first time, we can achieve attosecond time resolution in an electron transmission microscope, which we call 'ato-microscopy'. For the first time, we can see fragments of electrons in motion.”
Further information: Dandan Hui et al., Attosecond Electron Microscopy and Diffraction, Science Advances (2024). DOI: 10.1126/sciadv.adp5805. www.science.org/doi/10.1126/sciadv.adp5805
Provided by University of Arizona
Source: Freeze Frame: Researchers develop world's fastest microscope to observe electrons in motion (August 21, 2024) Retrieved August 21, 2024 from https://phys.org/news/2024-08-world-fastest-microscope-electrons-motion.html
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