Nobel Prize in Physics 2023
In 1905, Albert Einstein published the first explanation of the photoelectric effect, but at the time, it was impossible to resolve the timescales that were relevant for this effect. For a long time, physicists assumed the effect was instantaneous.
Einstein was eventually awarded the 1921 Nobel Prize in Physics “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect.” Parenthetically, when he gave his Nobel Prize lecture, it was not in Stockholm in December 1922 (Einstein was in Japan at that time), but in the middle of the summer of 1923, in Gothenburg – a unique event in the history of the Nobel Prize. His talk did not concern the photoelectric effect but the theory of relativity, the theory for which he was never awarded a Nobel Prize.
The fundamental question that this year’s physics laureates made it possible to pose was “what is the timescale for the photoelectric effect?” When an atom or a surface absorbs sufficient energy from incoming light, it can transfer that energy to an electron, which is then emitted with a kinetic energy equal to the photon energy minus the binding energy of the electron. The complex dynamics of atomic photoemission results in a small time delay, and the question is how small this time delay is. Before the window to attosecond science was opened, one could assume that the process occurred instantaneously, and so the research focus was on the energetics. This is the foundation of photoelectron spectroscopy.
The 2023 Nobel Prize in Physics has been awarded to 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.”
The 2023 physics laureates Pierre Agostini and Ferenc Krausz demonstrated ways to create shorter pulses of light than were previously possible.
Pierre Agostini and his research group in France succeeded in producing and investigating a series of consecutive light pulses, like a train with carriages. They used a special trick, putting the “pulse train” together with a delayed part of the original laser pulse, to see how the overtones were in phase with each other. This procedure also gave them a measurement for the duration of the pulses in the train, and they could see that each pulse lasted just 250 attoseconds.
At the same time, Ferenc Krausz and his research group in Austria were working on a technique that could select a single pulse – like a carriage being uncoupled from a train and switched to another track. The pulse they succeeded in isolating lasted 650 attoseconds and the group used it to track and study a process in which electrons were pulled away from their atoms.
These experiments demonstrated that attosecond pulses could be observed and measured, and that they could also be used in new experiments.
Now that the attosecond world has become accessible, these short bursts of light can be used to study the movements of electrons. It is now possible to produce pulses down to just a few dozen attoseconds, and this technology is developing all the time.
What is Attosecond?
An attosecond is an incredibly short unit of time equal to one quintillionth (10^-18) of a second. At this timescale, we can observe and manipulate extremely fast processes at the atomic and subatomic level.
The relationship between attoseconds and the photoelectric effect lies in the photoemission process, where photons (particles of light) strike a material's surface and release electrons from it. Understanding attoseconds is crucial because they allow scientists to investigate and control the ultrafast dynamics of the photoelectric effect, which was one of the key experiments that confirmed the quantum nature of light.
Attosecond pulses of light can be ugsed to study the precise timing and energy distribution of electrons ejected during photoemission. By using attosecond techniques, researchers can observe how electrons are liberated from atoms or solids in near real-time, gaining insights into the quantum mechanical interactions involved in the photoelectric effect. This knowledge is vital for applications in fields like ultrafast optics, materials science, and even for developing advanced technologies like attosecond X-ray sources for imaging atomic and molecular structures.
Relation Ship Between Attosecond and Photoelectric Effect
1. Photoelectric Effect Basics: The photoelectric effect is a phenomenon where electrons are emitted from a material's surface when it is exposed to light (photons). When a photon with sufficient energy strikes the material, it can transfer its energy to an electron, allowing it to escape from the material.
2. Time Scales: The photoelectric effect occurs extremely quickly, on the order of femtoseconds (10^-15 seconds) or even attoseconds (10^-18 seconds). At this timescale, understanding the precise dynamics of electron emission becomes crucial.
3. Attosecond Pulses: Scientists have developed techniques to generate attosecond pulses of light, which are incredibly short bursts of laser light on the attosecond timescale. These pulses are like "camera flashes" that allow researchers to capture snapshots of what happens during the photoelectric effect with extreme temporal precision.
4. Ultrafast Observations: Attosecond pulses enable scientists to observe the following aspects of the photoelectric effect in great detail:
- Ejection Timing: They can precisely measure the time it takes for an electron to be emitted after a photon's interaction with the material.
- Energy Distribution: Attosecond spectroscopy can reveal the energy distribution of the emitted electrons, providing insights into the quantum states involved.
- Quantum Effects: Attosecond studies help researchers understand the quantum nature of electron behavior during photoemission, such as tunneling and wave-particle duality.
5. Applications: The ability to study the photoelectric effect at attosecond timescales has practical applications. For example:
- In materials science, it aids in understanding and controlling processes like ultrafast electronic switching in semiconductors.
- In chemistry, it can shed light on chemical reactions happening on ultrafast timescales.
- In physics, it helps advance our understanding of quantum mechanics in action.
The Nobel Prize in Physics 2023 has been awarded for experiments with light that capture the shortest of moments.
This year’s physics laureates Pierre Agostini, Ferenc Krausz and Anne L’Huillier have conducted experiments that demonstrate a method for producing pulses of light that are brief enough to capture images of processes inside atoms and molecules.
Electrons’ movements in atoms and molecules are so rapid that they are measured in attoseconds. An attosecond is to one second as one second is to the age of the universe.
Attosecond pulses make it possible to measure the time it takes for an electron to be tugged away from an atom, and to examine how the time this takes depends on how tightly the electron is bound to the atom’s nucleus. It is possible to reconstruct how the distribution of electrons oscillates from side to side or place to place in molecules and materials; previously their position could only be measured as an average.
Attosecond pulses can be used to test the internal processes of matter, and to identify different events. These pulses have been used to explore the detailed physics of atoms and molecules, and they have potential applications in areas from electronics to medicine.
For example, attosecond pulses can be used to push molecules, which emit a measurable signal. The signal from the molecules has a special structure, a type of fingerprint that reveals what molecule it is, and the possible applications of this include medical diagnostics.
Now that the attosecond world has become accessible, these short bursts of light can be used to study the movements of electrons. It is now possible to produce pulses down to just a few dozen attoseconds, and this technology is developing all the time.
The 2023 Nobel Prize in Physics has been awarded to 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.”
