Wait a minute…

Gabriel Makhoul

 … and sixty quintillion attoseconds pass. That is a number approximately equal to sixty times the number of seconds that have passed since the beginning of the universe.  

 While this may just seem like a “fun” (not really) fact with big words that is ultimately unimportant to anyone, attoseconds were key to the 2023 Nobel Prize in Physics, awarded to physicists Pierre Agostini, Ferenc Krausz and Anne L’Huillier "for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter," and because they "have given humanity new tools for exploring the world of electrons inside atoms.” In this article we will discuss a) what this means and what the three physicists have done to warrant the Nobel and b) ways their discoveries could be impactful in the future, even in “everyday life”.

Image: Comparison of an attosecond, second and approximate age of the universe, Arstechnica.com

However, before we get to actually covering these two topics, we need to define an attosecond, as it is key to understanding the whole subject. An attosecond is a unit of time equal to 1×10-18 seconds, that is, in daily language, one quintillionth of a second. That means one billion billion attoseconds pass every second. Why is this even a thing? Because it’s the timescale at which electrons (hopefully we don’t need to define what they are) and other subatomic particles work. For example, it takes an electron about 320 attoseconds to jump from one atom to another, or about 150 attoseconds to move around the nucleus of a hydrogen atom. As such, attoseconds are quite useful as a measure of these very quick and small processes happening everywhere all the time.

Image: Ferenc Krausz, Anne L’Huillier, Pierre Agostini (left to right), Nature.com

 With this definition in mind, we can return to the 2023 Nobel Prize in Physics. As stated before, it was awarded "for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter.” Knowing what an attosecond is, this description starts making more sense. Their research made it possible for us to observe the behavior of electrons, which was impossible before. This is because they were able to experimentally come up with pulses of light so short they exist at the attosecond level, so we can now study electrons from up close by observing their interactions with the light. Since electrons are everywhere and are a fundamental particle that is responsible for things like chemical bonds, this could have a profound impact in the future.

This all began with Anne L’Huillier’s research in the late eighties, where she transmitted infrared laser waves through noble gasses. The infrared light passing through the gas produced much higher frequencies due to how the photons in the light interacted with the electrons of the gas. In the nineties a theoretical framework for this was worked out, but it wasn’t until later that the other two physicists’ contributions came.

In 2001, Pierre Agostini managed to succeed in turning Anne L’Huillier’s discovery into attosecond-short pulses experimentally, also developing a technique to measure how long the pulses last and to confirm that they indeed exist in the attosecond range. In the same year, Krausz worked on developing individual short pulses, as they originally only came in quick succession and were thus useless for any measurements. Moreover, using his laser technology, he managed to create a pulse that only lasted 650 attoseconds, being the first person to create one that lasted less than 1000 attoseconds.

In the following years, Krausz applied his discoveries to studying various phenomena related to electron interactions much closer, which, as stated already, had been impossible before. For example, he measured the speed of the photoelectric effect, which is the process of light ripping electrons off an atom.

While this all may still seem far removed from daily life, the implications are potentially profound. These methods could be very useful in medicine, for example, used to excite molecules in blood in order to detect very small changes and diagnose diseases such as cancer at a very early stage depending on the infrared light they emit. There are also applications in chemistry and biology, where attosecond pulses of light could be used to investigate processes involved in photosynthesis, etc. on a very small scale.

Pitruzzello, G. “A Bright Future for Attosecond Physics,” Nature.com, https://www.nature.com/articles/s41566-022-01031-w

Krausz, F., Corkum, P. “Attosecond Science,” Nature.com, 

https://www.nature.com/articles/nphys620

Lawler, D. “What Are Attoseconds? Nobel-winning Physics Explained.” Phys.org, https://phys.org/news/2023-10-attoseconds-nobel-winning-physics.html

Davis, N. “Nobel Prize in Physics Awarded to Three Scientists for Work on Electrons,” The Guardian, https://www.theguardian.com/science/2023/oct/03/nobel-prize-in-physics-awarded-to-three-scientists-for-work-on-electrons

Ouellette, J. “A New Time Window: Meet the Winners of the 2023 Nobel Prize in Physics,” Arstechnica.org, https://arstechnica.com/science/2023/10/nobel-prize-in-physics-honors-attosecond-pulses-to-study-electrons/

Castelvecchi D. “Physicists Who Built Fast “attosecond” Lasers win Nobel Prize,” Nature.com, https://www.nature.com/articles/d41586-023-03047-w