The subatomic world is difficult to image because it is not only incredibly small, but also super-fast. Now physicists at the University of Arizona have developed the world's fastest electron microscope to capture events that last just one quintillionth of a second.
A good camera with a shutter speed measured in milliseconds can take a clear photo of a person running. But the fastest “cameras” in the world—transmission electron microscopes—can capture events on the attosecond scale, such as photographs of electrons running. An attosecond is one quintillionth of a second, which makes a millisecond (one thousandth of a second) seem like an eternity.
To scale that up, there are as many attoseconds in one second as there are seconds in 31.7 billion years—more than twice the length of time the universe has existed. There are some truly mind-boggling numbers here.
Anyway, previous efforts to capture events on such timescales had gotten as short as 43 attoseconds—what researchers at the time called “the shortest controlled event ever created by humanity.” And now, the University A team has gone even shorter, freezing time to just one attosecond.
The new work builds on research by Pierre Agostini, Ferenc Krausz and Anne L'Huilliere, who produced the first pulses of light short enough to be measured in attoseconds, which earned the team the Nobel Prize in Physics in 2023.
For the new study, the researchers developed something they call an “attomicroscope.” First, a pulse of ultraviolet light is fired at a photocathode, which releases ultrafast electrons inside the attomicroscope. Then, a laser pulse is split into two beams, both of which are sent into the microscope at moving electrons. One of these beams is polarized and arrives at slightly different times, producing a “gated” pulse of electrons that can image a sample (in this case, graphene).
Using this technique, the team was able to produce electron pulses that lasted just a single attosecond, allowing them to observe ultrafast electron motion that is not normally visible. The researchers say the breakthrough could have applications in quantum physics, chemistry and biology.
“Improving the temporal resolution inside electron microscopes has been long awaited and has been the focus of many research groups, because we all want to see electron motion,” said Mohammed Hassan, one of the authors of the study. “These motions occur in attoseconds. But now, for the first time, we can achieve attosecond temporal resolution with electron transmission microscopy – and we call this 'attomicroscopy'. For the first time, we can see parts of the electron in motion.”
The research was published in the journal Science Advances.
Source: University of Arizona