Finally, physicists have a way to ‘see’ inside short-lived nuclei 

Finally, physicists have a way to ‘see’ inside short-lived nuclei 

Subject: Science and technology

Section: Msc

Introduction

• Physicists in Japan have made a significant breakthrough by developing a novel technique that allows them to “see” inside short-lived atomic nuclei, addressing a long-standing problem in nuclear physics.
• This development utilizes electron scattering and a sophisticated apparatus known as SCRIT (Self-Confining Radioactive-isotope Ion Target).

Early Efforts in Nuclear Exploration

• In the 19th century, scientists like Ernest Rutherford, Hans Geiger, and Ernest Marsden conducted experiments with radiation and gold foil, leading to the discovery of the dense central core in atoms containing mass and positive charge.
• Seven decades ago, Robert Hofstadter’s team used high-energy electrons to probe atomic nuclei, shedding light on charge and magnetic field arrangements within nuclei.
• These earlier experiments focused on stable atoms and their nuclei, utilizing other particles to delve inside them.

The RIKEN Nishina Center Breakthrough

• Researchers at the RIKEN Nishina Center for Accelerator-Based Science in Japan have now succeeded in using electron scattering to explore unstable nuclei, including those not found naturally.
• Their novel approach involves the utilization of SCRIT, an apparatus that can hold caesium-137 nuclei and facilitate electron interactions, thus allowing the exploration of short-lived nuclei.

The Advantages of SCRIT

• The SCRIT system involves accelerating electrons in a particle accelerator and colliding them with a block of uranium carbide, generating a stream of caesium-137 ions.
• SCRIT employs electric attractive forces to trap target ions along the electron beam in three dimensions, ensuring a high probability of electron-ion collisions.
• This setup minimizes the number of required caesium-137 ions, reducing the need for a vast quantity, which would otherwise be necessary.

Quantum Mechanics in Action

• The electron-ion interaction is studied by using a magnetic spectrometer to record interference patterns generated when scattered electrons behave like waves.
• Interactions involving electrons are advantageous because they are more predictable and well-understood, simplifying data analysis.
• Fine-tuning electron energy allows researchers to avoid complex particle interactions, enhancing the clarity of results.

Probing Nuclear Structure

• The RIKEN setup involves producing ions, transferring them to SCRIT, and subsequently colliding them with accelerated electrons.
• Magnetic spectrometer readings confirmed that the internal structure of a caesium-137 nucleus aligns with previous studies and theoretical calculations.

The Emergence of the Femtoscope

• The RIKEN team’s accomplishment can be likened to the development of a “femtoscope“, a tool capable of probing the femtometer scale of atomic nuclei (10^-15 meters).
• This innovation is significant as it aids physicists in addressing the persistent challenge of elucidating the structure of atomic nuclei, for which no unified theory exists.

Exploring Nuclear Quirks

• Over time, physicists have encountered various nuclear properties, such as the “island of stability”, where certain isotopes defy the usual trend of decay rate increasing with nucleus heaviness.
• The “island of stability” is characterized by a clustering of nuclei with a proton number of 112, known as the “magic number“.
• The existence of such islands remains unexplained, and physicists hope that the femtoscope technology can help bridge the gap between expected and unexpected nuclear shapes.
• Unstable nuclei with non-uniform densities of protons and neutrons may offer valuable insights into nuclear structure through femtoscope exploration.

Key Terms:

1. Atomic Nucleus: The central core of an atom, consisting of protons and neutrons, where most of the atom’s mass and positive charge are concentrated.
2. Electron Scattering: A technique in which high-energy electrons are directed at a target, and the scattering of these electrons provides information about the internal structure of the target.
3. Particle Accelerator: A device used to accelerate charged particles, such as electrons or protons, to high energies for various scientific and practical applications.
4. Femtoscope: A specialized instrument designed to probe the femtometer scale (10^-15 meters) of atomic nuclei, allowing for the exploration of nuclear structures.