Context: The Members of the Royal Swedish Academy of Sciences announced the Nobel Prize winners in Physics for 2023 for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter.
Nobel Prize in Physics:
- France’s Pierre Agostini, Hungarian-Austrian Ferenc Krausz and French-Swedish Anne L’Huillier won the Nobel Prize in physics for experimental methods that generate pulses of light measured in the attosecond (10-18 seconds) that enable the study of electrons inside atoms and molecules using attosecond spectroscopy.
- Electron 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.
Basic background:
- Analogy: In our everyday lives, we are unable to observe the processes completely that happen fast. For example, when a bullet is fired at an apple, we see the outcome — a smashed apple — but are unable to capture the entire process which takes barely a few milliseconds. However, a camera having a very high shutter speed makes it possible to see every step of the bullet piercing the apple and coming out of it, destroying the apple in the process.
- Dynamics at Atomic scale: At atomic and subatomic levels, processes (movement of electrons, or energy dynamics) happen at an incredibly fast rate, i.e., they take just a few picoseconds (a trillionth of a second, or 10-12 seconds) or femtoseconds (10-15 seconds). To observe these processes, scientists use unimaginably short pulses of light, like using extremely high shutter-speed cameras. But then they hit a barrier.
Existing challenges at sub-atomic scale:
- To observe any process, measurement must be made at a pace quicker than the rate of change.
- Light pulses which are the only plausible tool to capture processes at the atomic level cannot be made indefinitely shorter.
- Light consists of waves or vibrations in an electromagnetic field. The shortest possible pulse would have to be at least one cycle long, equivalent to its wavelength.
- Attoseconds science:
- Femtosecond pulses have enabled scientists to observe the processes happening at the atomic or molecular level.
- But at the sub-atomic level, dynamics of sub-atomic particles happen even faster, at the level of attoseconds. Ex. Dynamics of electrons are 100 to 1,000 times faster than that of an atom. (Lower the inertia, faster the dynamics).
- These femtosecond pulses were longer than the sub-atomic motion that was happening in a matter of attoseconds and the production of shorter pulses of light, in the attosecond range, did not seem possible.
- So, Scientists were unable to glimpse the motion of electrons with existing technologies, as for a long time, femtosecond ‘photography’ was considered the limit.
Nobel-winning research:
- The works of Pierre Agostini, Ferenc Krausz and Anne L’Huillier made it possible to observe phenomena happening at the timescale of Attoseconds as they demonstrated a way to create extremely short pulses of light that can be used to measure the rapid processes at which electrons operate.
- Working independently, the scientists devised experimental methods by mixing lights of different wavelengths to produce attosecond pulses of light which can enable the exploration of electron-dynamics in matter.
- The observation of every step of a process is necessary to fully understand it.
- It has made it possible to examine the rapid moves or changes in sub-atomic scales and allows scientists to control the process by tweaking the intermediate steps and obtaining desired results.
Potential Applications:
Attosecond science has potential applications in a variety of areas, from electronics to medicine, across disciplines in physics, chemistry and biology.
- In Electronics:
- Help 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.
- Reconstruct how the distribution of electrons oscillates from side to side in molecules and materials, earlier the distribution of electrons could only be measured as an average.
- Test internal processes of matter and identify different events.
- Attosecond physics can enable us to understand and control how electrons behave in a material.
- Help in designing more efficient electronic gadgets.
- In Medicine:
- Attosecond pulses can be used to identify different molecules, such as in medical diagnostics. Study molecular-level changes in blood to identify diseases.
- Krausz group has developed a new in vitro diagnostic analytical technique to detect characteristic molecular traces of diseases in blood samples. This technique allows monitoring of many molecules at the same time and the radiation is non-ionising and therefore not harmful.
