Scientists Studying High-Speed Electrons With Lasers Win Nobel Prize in Physics

Pierre Agostini, Ferenc Krausz and Anne L’Huillier created pulses of light so short that they can be used to observe the behavior of electrons

An image on a projector screen with photos of the three recipients of the 2023 Nobel Prize in Physics
From left to right, pictures of the three winners of the 2023 Nobel Prize in Physics: Pierre Agostini, Ferenc Krausz and Anne L’Huillier. L’Huillier is just the fifth women to receive the physics prize since the award's inception in 1901.  Jonathan Nackstrand / AFP via Getty Images

Three scientists were awarded the 2023 Nobel Prize in Physics on Tuesday for conducting experiments that showed it was possible to measure the behavior of fast-moving electrons.

At the atomic and subatomic level, particles move very short distances at astoundingly high speeds, which scientists previously considered impossible to observe. But physicists Pierre Agostini, Ferenc Krausz and Anne L’Huillier demonstrated how to create extremely short flashes of light that can be used to study electrons.

Their research, conducted separately, has potential applications to the fields of electronics, biology and medical diagnostics, as well as a range of other areas, according to a statement from the Nobel Committee.

“The reason we care about the electron is all chemistry… is all about how electrons interact,” Robert Rosner, a theoretical physicist at the University of Chicago, tells the Washington Post’s Joel Achenbach. “All atoms are a nucleus surrounded by clouds of electrons, and it’s these clouds of electrons that interact with each other that allow you to make molecules, to assemble stuff.”

“Once you can control and understand electrons, you have taken a very big step forward,” Nobel Committee member Mats Larsson said at the prize announcement, per David Keyton, Seth Borenstein and John Leicester of the Associated Press (AP).

Electrons move and their energies shift at the miniscule timescale of attoseconds. In one-billionth of a second, one billion attoseconds pass. This unit of time is so short that there are about as many attoseconds in one second as there have been seconds since the dawn of the universe—which was 13.8 billion years ago.

“At this time scale, time stands still for everything except the electrons,” Olle Eriksson, a physicist at Uppsala University in Sweden, tells the Washington Post.

To be able to observe electrons, researchers needed to produce ultra-short pulses of light, a method akin to using a short shutter speed to pick up fast movements with a camera or the way a strobe light makes actions appear frozen in stop motion. Up until the 1980s, scientists weren’t able to produce pulses of light shorter than a femtosecond—or one thousand attoseconds.

Shorter pulses of light can be produced by combining short light waves of varying wavelengths, according to materials provided by the Nobel Committee. In a 1987 experiment, L’Huillier and her colleagues in France achieved this by shooting an infrared laser through a noble gas. As the light interacted with electrons in the gas, it caused them to release pulses of light of various, higher wavelengths, known as overtones. Combining overtones in the right way can produce short light pulses only a few hundred attoseconds long.

Building on L’Huillier’s research, in 2001, Agostini and his colleagues in France became the first to produce pulses of light at the scale of attoseconds, per Nature News’ Davide Castelvecchi and Katharine Sanderson. In their experiment, they split laser light into two beams, passed one beam through a gas to get a series of extremely short pulses and recombined this wave with the second laser beam. This method allowed them to measure the length of the pulses, at just 250 attoseconds each.

Also in 2001, Krausz and colleagues in Austria found a way to isolate a single pulse lasting 650 attoseconds.

The research of these scientists showed that pulses of such a short length could be measured and used in experiments. The techniques developed by Agostini and Krausz are what are used by scientists today, Larsson said at the prize announcement. The shortest pulses produced today are only a few dozen attoseconds long.

“The drive for this research was extremely fundamental—can we create short pulses and what can we do with it?” L’Huillier said at a press conference, per Nature News. “It takes time to arrive at a point where we start to see applications for medicine, the semiconductor industry and for chemistry.”

Now, though, these techniques have been used to study the photoelectric effect, which refers to the emission of electrons when light hits an atom, as well as quantum tunneling, or when electrons pass through a barrier that classical mechanics says they shouldn’t have enough energy to pass through, write Science News’ Emily Conover and James R. Riordon.

“The ability to generate attosecond pulses of light has opened the door on a tiny—extremely tiny—timescale,” Nobel Committee member Eva Olsson said at the announcement. “And it’s also opened the door to the world of electrons.”

Of the 224 people to have received the Nobel Prize in Physics, L’Huillier is just the fifth woman, and the third since 2018, per Nature News.

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