Central Idea

In the world of atomic and nuclear physics, the quest to understand the inner workings of matter has been a constant journey of discovery.
Scientists have long sought ways to unravel the mysteries hidden within atomic nuclei, and recent breakthroughs in experimental techniques have taken us one step closer to achieving this goal.

Historical Milestones

150 years ago, scientists like Ernest Rutherford, Hans Geiger, and Ernest Marsden conducted experiments exposing a thin gold foil to radiation.
These experiments revealed that every atom has a dense central nucleus where mass and positive charge are concentrated.
Seven decades ago, physicist Robert Hofstadter led a team that bombarded thin foils with high-energy electrons, allowing scientists to probe atomic nuclei’s inner structure.

Researchers at the RIKEN Nishina Center for Accelerator-Based Science in Japan have demonstrated a setup using electron scattering to investigate unstable nuclei.
This advancement opens new avenues for understanding the fundamental building blocks of matter.

The SCRIT (Self-Confining Radioactive-isotope Ion Target) setup is more sophisticated than previous experiments using thin foils.
SCRIT can hold caesium-137 atom nuclei in place and facilitate electron interactions, a critical innovation.

Electrons are accelerated in a particle accelerator to energize them.
These energized electrons are directed at a block of uranium carbide, resulting in a stream of caesium-137 ions (atoms stripped of electrons).
The ions are transported to the SCRIT system, which traps target ions along the electron beam path using electric attractive forces.
This “overlap” ensures a high probability of electron-ion collisions.

Understanding the experimental setup’s probe into nuclear structure requires exploring interference patterns.
When light passes through a small hole, it creates concentric circles of light and dark patches due to interference.
Similarly, when an electron scatters off an atomic nucleus, it behaves like a wave during the interaction, resulting in interference patterns.
A magnetic spectrometer is used to record these interference patterns, offering advantages in clean and fine-tuned interactions.

The experimental results confirm the internal structure of the caesium-137 nucleus, aligning with previous studies and theoretical calculations.
The real significance lies in the development of the “femtoscope,” which can probe the femtometer scale (10^-15 meters) of atomic nuclei, unlocking new possibilities in nuclear physics.

The challenge in nuclear physics is the absence of a unified theory explaining atomic nuclei’s structure, despite various existing models.
Scientists encounter intriguing properties, such as the “island of stability,” where heavier nuclei of unstable elements defy the trend of faster decay via radioactivity.
This phenomenon raises questions about nuclear structure and the existence of stable clusters.

Researchers aim to use femtoscopes to explore nuclei with irregular shapes, bridging the gap between expected and unexpected nuclear structures.
This promises to illuminate the fundamental nature of atomic nuclei and advance our understanding of the universe at its most basic level.