The world of atomic nuclei is hard to image because it's not only incredibly tiny, but also incredibly fast. Now physicists at the University of Arizona have developed the world's fastest electron microscope, able to capture events that take place in just a trillionth of a second.
A high-end camera with a shutter speed measured in milliseconds might be able to take a clear photo of someone running, but the world's fastest “camera,” a transmission electron microscope, can capture events measured in attoseconds, such as photographs of electrons running. An attosecond is one-thousandth of a second, and a millisecond (one-thousandth of a second) feels like an eternity.
If you expand that, there are the same number of attoseconds in one second as there are seconds in 31.7 billion years – more than twice as long as the universe has existed. Some truly incredible numbers here.
Either way, previous efforts to capture events on such timescales had gotten it down to 43 attoseconds, which researchers at the time called “the shortest controlled event ever produced by mankind.” And now, a team from the University of Alberta has gone even further, freezing time at just 1 attosecond.
The new research builds on the work of Pierre Agostini, Ferenc Krauss and Anne Lhuilliere, who were the first to generate pulses of light short enough to be measured in attoseconds – work that has earned the team the Nobel Prize in Physics in 2023.
For this new study, the researchers developed a device they call an “ato microscope.” First, a pulse of ultraviolet light is shone on a photocathode, which releases ultrafast electrons inside the atto microscope. The laser pulse is then split into two beams and directed at the electrons traveling inside the microscope. One of the beams is polarized and arrives at slightly different times, creating a “gated” pulse of electrons that can be used to image the sample (graphene, in this case).
Diagram of the attomicroscope. A UV laser (pink) generates ultrafast electron pulses (green) inside the attomicroscope. The laser pulse is then split into two beams (orange) that hit the sample at slightly different times, generating a one-attosecond electron pulse to image the sample.
Using this technique, the team was able to generate electron pulses lasting just one attosecond, allowing them to observe ultrafast electron motions that are normally invisible — a breakthrough that the researchers say could have applications in quantum physics, chemistry and biology.
“Improved time resolution in electron microscopes has been a long-awaited goal and a focus of many research groups, because we all want to see electrons moving,” said study author Mohammed Hassan. “These movements happen on the attosecond time scale. But now, for the first time, we've been able to achieve attosecond time resolution in our electron transmission microscope, which we've named 'ato-microscopy'. For the first time, we can see electrons moving.”
The research was published in the journal Science Advances.
Source: University of Arizona
