For over a century, physicists have known that virtually every chemical reaction, biological process, electrical current, and solar-panel energy conversion in the universe is driven by the rapid movement of electrons jumping between atoms and across molecular bonds. Yet actually filming an electron in the act of moving inside matter seemed physically impossible. Because electrons zip through atoms at fractions of the speed of light, any camera shutter slower than a billionth of a billionth of a second produces nothing but a hopeless blur. Now, by upgrading a transmission electron microscope to fire pulses lasting just a single attosecond, physicists have built the world’s fastest “attomicroscope”—capturing real-time movies of electrons in motion.
How Fast Is an Attosecond?
To grasp the engineering breakthrough behind the attomicroscope—developed in 2024 by a team of physicists led by Associate Professor Mohammed Hassan at the University of Arizona—one must first comprehend the mind-bending brevity of an attosecond ($10^{-18}$ seconds):
- An attosecond is one quintillionth (a billionth of a billionth) of a single second.
- In a single standard second, a beam of light can travel roughly three hundred thousand kilometers—fast enough to circle the entire equator of planet Earth seven and a half times.
- In a single attosecond, that exact same beam of light barely has time to travel across the width of three water molecules (about 0.3 nanometers)!
- To put the scale in perspective: there are more attoseconds inside a single tick of your wristwatch than there have been seconds since the Big Bang created the universe 13.8 billion years ago.
From the 2023 Nobel Prize to the “Attomicroscope”
While regular scanning and transmission electron microscopes (TEMs) have long been able to take razor-sharp still photographs showing the arrangement of atoms inside a crystal—because high-energy electron beams have wavelengths thousands of times smaller than visible light—they lacked the shutter speed to capture what the electrons around those atoms were doing between frames. In 2023, the Nobel Prize in Physics was awarded to Pierre Agostini, Ferenc Krausz, and Anne L’Huillier for pioneering extreme-ultraviolet laser pulses measured in attoseconds.
Building directly upon that foundation, the University of Arizona researchers modified a transmission electron microscope to split a powerful laser into two ultra-fast synchronized beams paired with an electron beam:
- The Pump Laser Pulse: First, an ultra-fast optical laser pulse strikes the microscopic material sample (in the landmark experiment, a single-atom-thick sheet of carbon known as graphene), kicking the electrons inside the graphene atoms into active motion.
- The Gating Attosecond Electron Pulse: Next, by using polarized laser light as an optical “shutter” to slice a continuous beam of electrons into ultra-short packets lasting just one single attosecond (625 attoseconds down to 1 attosecond), the microscope fires these electron bullets straight through the sample like a camera flash.
- Stroboscopic Stop-Motion Film: By varying the delay between the first laser kick and the attosecond electron flash by tiny fractions of an attosecond and stitching the frames together—exactly like nineteenth-century pioneer Eadweard Muybridge used a row of tripwire cameras to prove all four hooves of a galloping horse leave the ground—the team produced the first direct movies of an electron cloud shifting and flowing across carbon bonds inside solid matter.
Why Watching Electrons Changes Everything
Being able to watch how an electron actually moves from point A to point B inside a molecule transforms quantum physics from theoretical equations on a chalkboard into an observational visual science:
- Next-Generation Electronics and Quantum Computing: Engineers can directly observe why electrons experience resistance or lose quantum coherence inside two-dimensional semiconductors and superconductors, allowing them to design computer chips that operate at light wave frequencies (petahertz speeds—a million times faster than today’s gigahertz processors).
- Clean Energy and Artificial Photosynthesis: Chemists can film the exact attosecond moment a photon of sunlight strikes a solar cell or a chlorophyll leaf molecule and knocks an electron loose, designing ultra-efficient solar fuels and targeted pharmaceuticals from the electron up.
