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Saturday, December 2, 2023
Dr. Brown: Tracking electrons: The Nobel Prize in physics
Physicist Anne L’Huillier was part of the team that won the Nobel Prize in physics in 2023, for creating ultra-short wavelength light beams. WIKIPEDIA

In 2018, Canadian physicist Donna Strickland received the Nobel Prize for physics, alongside French scientist Gérard Mourou, her doctoral supervisor.

Her contribution was related to successfully increasing the power of brief pulses of laser light without destroying the laser in the process.

To do so, she stretched the wavelength of the laser beam and increased its amplitude (energy) before shortening the beam to its original wavelength.

In a sentence, it all sounds so easy, but as with most scientific and engineering ventures, the devil was in getting the details right.

Almost a hundred years earlier, Werner Heisenberg was awarded a Nobel for his uncertainty principle as a fundamental property in quantum mechanics.

He showed it was impossible to determine both the position and momentum of an electron at the same time because the energy of any illuminating beam designed to determine those properties would destroy the electron.

Since 1927, Heisenberg’s uncertainty principle has been widely accepted as one of the core properties of quantum mechanics.

His theorem was at the heart of last year’s Nobel in physics. It was awarded to John Clauser, Alain Aspect and Anton Zeilinger for their work that proved entangled particles, such as electrons, remain entangled, whatever the distance between them.

This marked the triumph of quantum mechanics over Albert Einstein’s challenge to this field of study: more than five decades prior, Einstein made his strongest claim that uncertainty and other weird properties of quantum mechanics made no sense, even if the practical applications of quantum mechanics worked brilliantly.

This year’s Nobel might well challenge Heisenberg’s uncertainty principle, for if single electrons can be tracked in atoms and molecules, what was uncertain might prove to be certain.

But that’s not why this year’s laureates launched their studies.

Their goal was to develop illuminating beams with wavelengths short enough to identify and understand the behaviour of electrons, and hence the bonding properties, which bind atoms together to form molecules.

Until their studies, that goal seemed impossible.

The 2023 Nobel in physics was awarded to Anne L’Huillier, Pierre Agostini and Ferenc Krausz for creating ultra-short wavelength light beams, brief enough to illuminate electrons in atoms and molecules.

Success came first with L’Huillier’s discovery in 1983 that an infrared laser light illuminating a noble gas, excited electrons in the gas, generating short wavelengths, which corresponded to harmonic frequencies of the laser light’s fundamental frequency.

The trick was to combine those harmonic frequencies in such a way that wavelengths as short as several hundred attoseconds in length were created – short enough to study electrons.

That goal was reached independently by Pierre Agostini and Ferenc Krausz, with similar results.

(One attosecond is a millionth of a trillionth of a second in duration – the number of them in one second is the same as the number of seconds since the universe began – staggering and numbing numbers.)

Summing up the reasons for this prize, the Nobel committee stated that L’Huillier, Agostini and Krausz demonstrated a way to create extremely short pulses of light that can be used to measure the rapid processes in which electrons move or change energy.”

“L’Huillier discovered a new effect from laser light’s interaction with atoms in a gas. Agostini and Krausz demonstrated that this effect can be used to create shorter pulses of light than previously were thought possible,” the committee concluded.

The committee was less forthcoming about what practical results might come from these discoveries, except to measure the “tightness” of bonds in molecules.

Beyond the official comments on the achievements of the laureates is the potential to study, what for almost a century, was considered uncertain by Heisenberg.

That, for me, is the big but unstated story with this prize.

Will frame-by-frame resolution at the subatomic level ever reach a level at which two or more properties of electrons can be studied?

If that happens in the future – and the tools are getting better and better – perhaps what was uncertain may become certain with much better tools for observing electrons in real-time.

The seventh annual review of the Nobel Prizes began Nov. 1 with the physics prize. Chemistry, medicine, economics, peace and literature will follow.

Sign up with Debbie Krause (dkrause@notlpl.org) at the Niagara-on-the-Lake Public Library.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.  

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