Physicists have developed the world's fastest microscope, so fast it can spot electrons in motion.
The new device is a type of transmission electron microscope that takes images of electrons in flight by bombarding them with electron pulses lasting one-hundred trillionth of a second.
This is quite a feat: an electron travels at approximately 1,367 miles per second (2,200 kilometers per second), and can circle the Earth in just 18.4 seconds.
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By observing the particles under a microscope, the researchers hope to discover new insights into how they fly. They published their findings August 21 in the journal Science Advances.
“This transmission electron microscope is like the very powerful camera in your latest smartphone, able to take pictures of previously invisible things like electrons,” Mohammed Hassan, an associate professor of physics and optical sciences at the University of Arizona and lead author of the paper, said in a statement. “We hope this microscope will enable the scientific community to understand the quantum physics behind the behavior and movement of electrons.”
How electrons arrange and rearrange themselves inside atoms and molecules is an important question in both physics and chemistry, but it's incredibly difficult to study due to the energetic nature of these tiny particles.
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To create exposure times long enough to capture the electrons' movements, physicists in the early 2000s developed a way to generate pulses as short as attoseconds (1X10^-18 seconds), an advance that earned the scientists the 2023 Nobel Prize in Physics.
By shortening microscope exposure times to the scale of a few attoseconds (one attosecond is one second, the age of the universe), physicists have worked out how electrons carry charge, how they behave in semiconductors and liquid water, and how chemical bonds between atoms can be torn apart.
But even the scale of a few attoseconds is too large to capture the individual movements of electrons. To achieve this, the physicists in the new study tweaked their electron gun so that it could produce pulses that were just one attosecond long.
These pulses strike the “sample” being studied, and as the electrons pass through the sample they slow down, changing the shape of the electron beam's wavefront. The decelerated beam is then expanded by lenses, causing any fluorescent material it strikes to glow.
By combining an electron pulse with two carefully synchronized light pulses (which excite electrons in the material into motion and help generate the electron pulse, respectively), they were able to probe the ultrafast motion of electrons inside atoms.
“We've been able to achieve attosecond time resolution in electron transmission microscopy, which we've named 'ato-microscopy,'” Hassan says. “For the first time, we can see fragments of electrons in motion.”
