ATTOSECOND

ATTOSECOND

CONTEXT:

• Recently the 2023 Nobel Prize for physics was awarded to Anne L’Huillier, Pierre Agostini, and Ferenc Krausz “for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter”.

WHAT IS ATTOSECOND ?

• An attosecond is an astonishingly short unit of time, equivalent to one quintillionth of a second, or 10 to the power of 18 seconds.
• This is the timescale at which the properties of an electron change.
• So, to truly understand electrons, it should be possible to study them at these timescales.
• This is what the work of the Nobel laureates made possible.
• Attosecond science, including attosecond physics, or attophysics, deals with the production of extremely short light pulses and using them to study superfast processes

CHARACTERSTICS OF ATTOSECOND PHYSICS :

The main interests of attosecond physics are:

• Atomic physics: investigation electron correlation effects, photo-emission delay and ionization tunneling.
• Molecular physics and molecular chemistry: role of electronic motion in molecular excited states (e.g. charge-transfer processes), light-induced photo-fragmentation, and light-induced electron transfer
• Solid-state physics: investigation of exciton dynamics in advanced 2D materials, petahertz charge carrier motion in solids, spin dynamics in ferromagnecti materials.
• The 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, according to the Nobel Prize Committee.
• For example, attosecond pulses can be used to push molecules, which emit a measurable signal.

ABOUT ATTOSECOND PULSE :

• The concepts underlying the production of attosecond pulses come from wave mechanics.
• In 1988, Anne L’Huillier and her colleagues in Paris passed a beam of infrared light through a noble gas.
• They found that the gas emitted light whose frequency was a high multiple of the beam’s frequency for example, if the beam frequency was 10 arbitrary units, the emitted light had frequencies of 50 units, 60 units, 70 units, etc.
• This phenomenon is called high ­harmonic generation, and the emitted waves are said to be overtones of the original.
• The researchers also found a way to describe this process using the equations of quantum mechanics.
• These equations also explained why the intensity of the re­emitted light plateaued as the beam frequency was increased.

HOW ATTOSECOND PULSE IS PRODUCED ?

• When the infrared beam strikes the noble gas atoms, it produces multiple overtones.
• If the peak of one overtone merges with the peak of another, they undergo constructive interference (like in the double­slit experiment) and produce a larger peak.
• When the peak of one overtone merges with the trough of another, however, they undergo destructive interference, ‘cancelling’ themselves out.
• By combining a large number of overtones in this way, physicists could fine ­tune a setup to produce light pulses for a few hundred attoseconds due to constructive interference and then stop, due to destructive interference.
• These pulses are produced only when the beam’s frequency is within the plateau range.

APPLICATIONS OF ATTOPHYSICS :

• One of the primary areas where attoseconds have revolutionised our understanding is in the realm of atmic and moleculat physics.
• One of the primary goals of attosecond science is to provide advanced insights into the quantum dynamics of electrons in atoms, molecules and solids with the long-term challenge of achieving real-time control of the electron motion in matter.

• At this timescale, researchers can now capture the dynamics of electrons within atoms and molecules, allowing them to witness the incredibly fast processes that govern chemical reactions and electronic behavior.
• The devices used to produce attosecond pulses cost crores of rupees, great skill to operate, and are bulky.
• But miniaturisation has been an important form of technological progress in the last century and, someday, we may have pocket­ sized gizmos to study electrons.
• The important thing is we know how to achieve it.
• Science has had its own variety of miniaturisation microbiology, femtochemistry, attophysics facilitated by devices that could see smaller and smaller things.
• When atoms interact with strong laser fields, high-order harmonics are generated.
• In the time domain, this radiation consists of ultrashort “attosecond” light pulses with central photon energy in the extreme ultraviolet (XUV) energy domain and duration of the order of 100 as.
• Attosecond science consists in generating attosecond pulses and in using them to study ultrafast dynamics.
• The time scale is that of the electron motion in atoms, molecules or more complex systems.
• Temporal information can be obtained either by pump probe techniques or by phase and amplitude measurements over a large spectral range.

WAY FORWARD:

• The fundamental significance of attoseconds in physics lies in their ability to shed light on phenomena that were previously hidden from our view.
• As researchers continue to improve their ability to produce attosecond light pulses, they’ll gain a deeper understanding of the basic particles that make up matter.

SYLLABUS: MAINS, GS-3, SCIENCE AND TECHNOLOGY

SOURCE: THE HINDU