Context- The 2023 Nobel Prize for Physics was shared by three scientists—Pierre Agostini,
Ferenc Krausz and Anne L’Huillier—for their “experimental methods that generate attosecond
pulses for the study of electron dynamics in matter.”
- An attosecond (symbol as) is a unit of time in the International System of Units (SI) equal
to 1×1018of a second (one quintillionth of a second).
- For comparison, an attosecond is to a second what a second is to about 31.71 billion
- An attosecond is equal to 1000 zeptoseconds, or 1⁄1000 of a femtosecond.
- Attosecond physics, also known as attophysics, is a branch of physics that deals with
light-matter interaction phenomena wherein attosecond (1018 s) photon pulses are used
to unravel dynamical processes in matter with unprecedented time resolution.
- Attosecond physics gives us the opportunity to understand mechanisms that are
governed by electrons.
- Their experiments have allowed scientists to produce ultra-short pulses of light, with
which they can finally ‘see’ directly into the super-fast world of electrons.
Why electrons weren’t ‘seen’ before
- Electrons which are negatively charged particles of an atom, move very fast in the
nucleus of an atom. To see the sharper and clear movement of electrons we need a
camera with exposure time to the order of attoseconds.
How fast is electron dynamics?
- The movement of an atom in a molecule can be studied with the very shortest pulses
produced by a laser. These movements and changes in the atoms occur on the order of
femtoseconds—a millionth of a billionth of a second. But electrons are lighter and
interact faster, in the attosecond realm.
- All light consists of waves of electric and magnetic energy. Each wave has a sinusoidal
shape—starting from a point, going up to a peak, dipping into a trough, and finally
getting back to the same level as the starting point.
- By the 1980s scientists produced light pulses whose duration was a few femtoseconds.
But seeing electrons required an even shorter flash of light and scientists were unable to
produce a pulse of light shorter than a femtosecond.
How can even shorter pulse be created?
- In 1987, Anne L’Huillier and her colleagues noticed the ‘overtones’ (waves of light whose
wavelength was an integer fraction of the beam) after passing an infrared laser beam
through a noble gas.
How is an attosecond pulse created?
- Physicists found that the overtones emitted were in the form of ultraviolet light. As
multiple overtones were created in the gas, they began to interact with each other.
- When the peak of one overtone merges with the peak of another, they produce an
overtone of greater intensity, through constructive interference. But when the peak of
an overtone merges with the trough of another, they cancel each other out, in
- Scientists realized that it should be possible to create intense pulses of light each a few
attoseconds long (due to constructive interference), with destructive interference
ensuring that they didn’t last for longer.
- In 2001,Pierre Agostini and his research group in France successfully produced and
investigated a series of 250-attosecond light pulses, or a pulse train.
- In the same year, Ferenc Krausz and his team in Austria developed a technique to
separate an individual 650-attosecond pulse from a pulse train.
- Using that, the researchers were able to measure the energy of some electrons released
by some krypton atoms.
What are the applications of attosecond physics?
- It allows scientists to capture ‘images’ of activities that happen in incredibly short time
- Scientists can use such pulses to explore short-lived atomic and molecular processes
implicated in fields like materials science, electronics, and catalysis.
- For medical diagnostics,attosecond pulses can be used to check for the presence of
certain molecules based on their fleeting signatures.
- These pulses could also be used to develop faster electronic devices, and better
telecommunications, imaging, and spectroscopy.