Electron microscopy has existed for nearly a century, but a record-breaking modern iteration finally achieved what physicists have waited decades to see—for the first time, a transmission electron microscope is capturing an electron with such clarity they can see its individual components. Researchers believe they have unlocked an entirely new realm of optical science they are now calling “attomicroscopy” that will influence the worlds of quantum physics, biology, and chemistry.
The breakthrough comes from a team led by experts at the University of Arizona and is detailed in a new study published August 21 in Science Advances. Mohammed Hassan, a UA associate professor of physics and optical sciences, likens transmission electron microscopes to a smartphone’s camera.
“When you get the latest version of a smartphone, it comes with a better camera,” Hassan said in an accompanying university statement on Wednesday. “… With this microscope, we hope the scientific community can understand the quantum physics behind how an electron behaves and how an electron moves.”
[Related: Winners of the 2023 Nobel Prize in physics measured electrons by the attosecond.]
While the original electron microscope arrived in the early 1930’s (there’s still a controversy to this day over who invented the very first one), scientists have relied on what are known as transmission electron microscopes since the 2000s. In these devices, objects are magnified millions of times their size far beyond what light microscopes can accomplish. This is due to their reliance on pulses of electron laser beams fired at a target. From there, extremely precise camera sensors and lenses image these atomic particles as they pass through the sample. The changes observed in a subject between these images is what is called a microscope’s temporal resolution. To increase the resolution, researchers have turned to speeding up those laser bursts down to attoseconds lasting just quintillionths of a second.
But even here, the problem is “attoseconds,” plural. If physicists ever hoped to capture a single electron frozen in place and detail its incomprehensibly fast subatomic reactions and interactions, they would need a transmission electron microscope capable of firing a single attosecond pulse. To make this a reality, researchers turned to the work pioneered by 2023’s winners of the Nobel Prize in Physics, who generated the first extreme ultraviolet radiation pulse, also measured in attoseconds. With that foundation, the team finally achieved that one-attosecond benchmark.
To do so, researchers developed and built a new microscope that splits its laser into a single electron pulse and two pulses of ultrashort light. The first light pulse, called a pump pulse, energizes a sample’s electrons. Next, what’s known as an optical gating pulse initiates, allowing an infinitesimal timeframe for a one-attosecond electron pulse to then emit from the microscope. Once the two ultrashort light pulses are properly synchronized, operators time the electron pulses to help capture atomic events at an attosecond-level temporal resolution.
“The improvement of the temporal resolution inside of electron microscopes has long been anticipated and the focus of many research groups,” Hassan said on Wednesday. “… For the first time, we can see pieces of the electron in motion.”
According to the study’s abstract, the attosecond microscope will allow physicists, optical scientists, and other experts to study electron motion in unprecedented detail and “directly connect it to the structural dynamics of matter in real-time and space domains.” This, they say, will hopefully pave the way for “real-life attosecond science applications in quantum physics, chemistry, and biology.”
