A Nobel Prize for One Quintillionth of a Second
The 2023 Nobel Prize in Physics has been awarded to three pioneering scientists - Pierre Agostini, Ferenc Krausz, and Anne L’Huillier - for generating the shortest flashes of light ever produced. Their work has enabled scientists to observe the motions of electrons in real time for the first time.
These researchers developed techniques to create pulses of light that last for just an attosecond. What’s an attosecond? It’s an incredibly short period of time - just a quintillionth of a second. To grasp how fast that is, a femtosecond (one quadrillionth of a second) seems long in comparison.
The Nobel Prize recognizes the groundbreaking achievements of Agostini, Krausz and L’Huillier in pushing the boundaries of time resolution. By developing the capability to generate ultrashort bursts of light lasting just an attosecond, they have enabled scientists to probe and essentially "freeze" the ultrafast motions of electrons within atoms, molecules and materials to study their dynamics.
This new capability opens up many exciting opportunities for discoveries in physics, chemistry, biology, and more by visualization ultrafast processes never directly seen before. The pioneering work of these 2023 Nobel Prize recipients has brought the once-distant dream of observing electron motions in real time into reality.
In this post, we’ll explain the science behind how these incredible attosecond light pulses are generated and how they enable new observations that are revolutionizing our comprehension of the quantum world. Join us on a journey to grasp the feats of engineering and ingenuity behind one quintillionth of a second!
The Journey to Attosecond Science Began with the Photoelectric Effect
The field of attosecond physics owes its origins to early 20th century experiments on the photoelectric effect. Upon shining light on a material, scientists like Hertz, Lenard, and Hallwachs discovered that electrons were emitted.
Albert Einstein provided the explanation in 1905, recognizing that light energy is absorbed and transferred to electrons in quantized packets of energy called photons. By absorbing enough photon energy to overcome its binding, an electron can be ejected from an atom or material.
This began the recognition that light and electrons interact in the quantum realm. However, the early 20th century view was that this light-electron interaction occurred essentially instantaneously.
A new frontier emerged: determining just how quickly does this light-triggered electron emission happen? What is the actual timescale of the photoelectric effect?
Probing this required light pulses shorter than the femtosecond resolution possible in the 1980s and 90s. Generating attosecond pulses finally provided the capability to resolve the ultrafast dynamics governing the interaction between light and matter.
With the work of Agostini, Krausz, L’Huillier and others, the dream of directly accessing the microcosm of electron motions initiated by the quantum revolution could become a reality. Their pioneering achievements pushed open the door to the new vista of attosecond science.
Theoretical Foundations for Resolving Electron Timescales
Before the possibility of generating attosecond pulses experimentally, some key theoretical work helped motivate the pursuit of ever shorter light pulses.
In the early 1980s, for example, theoretical physicist T.W. Hänsch proposed that the broad spectral bandwidth needed for ultrashort pulses could be obtained by combining several laser beams with different colors.
Around the same time, Gy. Farkas and Cs. Tóth predicted that ultrashort extreme UV pulses could be produced by high harmonic generation. This theoretical proposal was validated later in experiments.
So while the technical achievement of actually generating isolated attosecond pulses experimentally was groundbreaking, important theoretical work on ideas like utilizing high harmonic generation had planted seeds for resolving electron timescales using ultrafast light pulses.
Building on these foundations, pioneering experimental work like that of Nobel laureates Pierre Agostini, Ferenc Krausz, and Anne L'Huillier opened the door to attosecond science by realizing and measuring pulses on these scales for the first time in the lab.
Their work marrying theory and ingenious experimental implementation represents the major leap that enabled studying ultrafast electron motions that were previously hidden from view. More work remains to fully understand and harness attosecond pulses, but the landscape is now transformed by what their innovations have made experimentally real.
Pioneering Attosecond Pulse Generation
As the scientific background describes, Anne L’Huillier played a key role in theoretically explaining the process of high harmonic generation (HHG). This refers to when an intense laser pulse applied to a gas generates very high frequency light at odd harmonics of the original laser frequency.
In 1991, L'Huillier helped explain that HHG results from electrons released by the intense laser field, accelerating, and then recombining with their parent ions. This recollision converts the electron energy into a burst of extreme UV photons - an insight that became known as the rescattering model.
L’Huillier recognized that the plateau seen in HHG spectra where intensity stays high over many harmonics provided the broad bandwidth needed for extraordinarily short pulse generation.
Meanwhile, Ferenc Krausz’s group experimentally demonstrated very high harmonic cutoffs and broadband spectra by using few-cycle laser pulses in gases. This provided the large continuum of frequencies necessary.
In 2001, Krausz’s team then combined few cycle pulses with spectral filtering to isolate a single attosecond burst for the first time. This groundbreaking advance generated a reproducible isolated 650 attosecond pulse of extreme UV light.
On a parallel track, Pierre Agostini’s group developed the RABBIT technique in the 1990s to enable measurements of pulses in attosecond ranges by photoionizing gases with a synchronized combination of XUV and laser light.
Building on this, Agostini’s team combined RABBIT with HHG to generate and characterize a regular train of 250 attosecond pulses, another pioneering milestone.
Together, these advances realized reproducible attosecond pulse generation. By solving key problems like isolation and metrology, the laureates enabled the new frontier of attosecond science - direct access to electron timescales.
Revolutionary Applications of Attosecond Pulses
The reproducible isolation of attosecond light bursts has opened up many new explorations of ultrafast electron motion. Some highlights:
- Delayed photoemission - Attosecond pulses revealed delays between electron emissions from different atomic orbitals, showing dynamics affect this quantum process.
- Gas vs liquid differences - Attosecond probes measured time delays in electron release between gas phase and liquid water molecules, exposing environmental impacts.
- Pump-probe experiments - Precisely timed attosecond pulses act as pump and probe allowing causality in light-matter interactions to be mapped.
- Materials science - Solid state dynamics like differences between localized and delocalized electrons in metals are being studied on their natural femto-attosecond timescales.
- Biological frontiers - Attosecond techniques may enable studying electron dynamics in proteins and other biomolecules by resolving charge migration.
The unprecedented temporal clarity of attosecond pulses is revolutionizing our perception across physics, chemistry, biology, and materials science. Many strange quantum processes in the microcosm can now be freeze-framed and filmed like never before. The future horizons opened up by attosecond science are tremendously exciting.
The Lasting Impact of Attosecond Science
The pioneering work honored by the Nobel Prize is redefining the landscape of ultrafast science. For the first time, the motions of electrons can be tracked in real time.
This new capability for direct observation allows fundamental processes involving electron dynamics to be visualized and studied in detail across many fields:
- Chemistry - The making and breaking of chemical bonds can be filmed as electron densities shift. Reactions with transition states lasting just femtoseconds are now resolvable.
- Physics - Interactions between light and matter at quantum scales can be explored like never before. New vistas in areas from condensed matter to quantum electrodynamics are opening.
- Materials Science - The interplay between electrons in complex solids can be measured down to femtosecond and attosecond timescales to better understand exotic material properties.
- Technology - Pushing the engineering limits of ultrafast laser pulses and measurement techniques has tangible technological benefits for lasers, optics, and electronics.
For decades, the ~5-10 femtosecond barrier persisted as the shortest resolvable timescale. Generation of isolated attosecond bursts has smashed through this limitation, opening up the new landscape of attosecond science.
The implications for fundamental knowledge and technical innovation promise to be far-reaching thanks to the pioneering work recognized by the 2023 Nobel Prize in Physics.
Conclusion
Exploring Attoseconds: The Journey Continues
The groundbreaking achievements recognized by this year’s Nobel Prize have opened a portal into the world of ultrafast electron motion on its natural attosecond timescales. While we have taken first steps into this new vista, many strange quantum processes remain to be explored in full detail.
The future horizons of attosecond science promise many surprising discoveries that will reshape our comprehension of physics, chemistry, biology, and materials science at their most fundamental levels. Pushing technology to its very limits of precision control has expanded our capability to observe the natural world.
As we continue to illuminate the crucial dynamics that occur on the timescale of electron motions, new knowledge and innovations will certainly arise thanks to the lasting legacy of Agostini, Krausz, L’Huillier and their pioneering work recognized with the 2023 Nobel Prize in Physics. Their achievements have launched a new epoch for probing and harnessing the microcosm of ultrafast science.