three nucleon force nuclear stability heavy elements study

New Study Unveils Overlooked Nuclear Force That Stabilizes Matter

Kyushu University Researchers Discover  Three-Nucleon Force's Role in Nuclear Stability

Researchers at Kyushu University, have uncovered how the three-nucleon force within an atom's nucleus influences nuclear stability. Their study in Physics Letter B sheds light on why certain nuclei are more stable and offers insights into astrophysical processes, such as the formation of heavy elements in stars.

The Nucleus: The Heart of Atomic Matter

Atoms, the fundamental constituents of matter, serve as the building blocks of the universe. The majority of an atom's mass is concentrated in its minuscule nucleus, which consists of protons and neutrons, collectively termed nucleons. For over a century, a key focus in nuclear physics has been understanding the interactions between these nucleons that ensure nuclear stability and maintain a low-energy state.

The Two-Nucleon Force: The Strongest Nuclear Interaction

The strongest nuclear interactions is the two-nucleon force, which acts as an attractive force at long range, drawing two nucleons together, while repelling them at short range to prevent excessive proximity.

The Complexity of the Three-Nucleon Force

"Researchers have gained a solid understanding of the two-nucleon force and its influence on nuclear stability," say Tokuro Fukui, Assistant Professor at Kyushu University's Faculty of Arts and Science. "However, the three-nucleon force, involving interactions among three nucleons at once, remains far more complex and not yet fully understood."

Illustrating the Nuclear Forces with a Game of Catch

Fukui illustrates nuclear forces by comparing them to a game of catch. In the case of the two-nucleon force, two nucleons interact by tossing a ball, which represents a subatomic particle called a meson. The meson's mass varies, with the pion, the lightest meson, being responsible for the long-range attraction between nucleons.

The Three-Nucleon Force: A More Complex Interaction

In the case of the three-nucleon force, three nucleons interact, passing mesons or balls between them. Simultaneously, while tossing and catching the mesons, the nucleons also spin and orbit within the nucleus.

Recent Research Highlights the Importance of the Three-Nucleon Force

While the three-nucleon force has traditionally been regarded as less significant than the two-nucleon force, recent research is increasingly recognizing its importance. This new study elucidates the mechanism by which the three-nucleon force contributes to nuclear stability, showing that its influence strengthens as the nucleus increases in size.

Advanced Research Methods: Supercomputer Simulations and Nuclear Theory

Through their research, Fukui and his team used advanced nuclear theory and supercomputer simulations to analyze the exchange of pions between three nucleons. They identified that two pions exchanged between nucleons result in restricted movement and spin, leaving only four potential combinations. Their calculations revealed that the "rank-1 component" among these combinations is vital for nuclear stability.

Spin-Orbit Splitting and Nuclear Stability

Fukui explains that the increased stability arises from the enhancement of a phenomenon known as spin-orbit splitting. When nucleons spin and orbit in the same direction, their alignment lowers the system's energy. However, when they spin and orbit in opposite directions, the nucleons occupy a higher energy state. This results in nucleons "splitting" into distinct energy levels, contributing to the stability of the nucleus.

Simulations Show the Greater Impact on Nucleons with Opposing Spins

According to Fukui, their supercomputer simulations indicated that the three-nucleon force increases the energy of nucleons with aligned spins and orbits, but has an even greater effect on nucleons with opposing spins and orbits. This results in a broader energy gap between shells, further stabilizing the nucleus.

Implications for Heavier Elements and Fusion Processes

This effects is particularly notable in heavier nuclei with a higher number of nucleons. In carbon-12, the heaviest element studied with 12 nucleons, the three-nucleon force led to a 2.5-fold expansion of the energy gap.

Fukui states, "The effect is so pronounced that it almost equals the influence of the two-nucleon force. We foresee a stronger impact in heavier elements beyond carbon-12, which we aim to study in our upcoming research."

The Role of Three-Nucleon Force in Element Formation in Stars

The three-nucleon force may be crucial in explaining how heavy elements emerge from the fusion of lighter elements in stars. As this force intensifies in heavier nuclei, it enhances their stability by widening the energy gaps between nuclear shells.

Enhanced Stability and Its Impact on Neutron Capture

This enhanced stability makes it harder for the nucleus to capture additional neutrons, a critical step in forming heavier elements. When the nucleus contains a "magic number" of protons or neutrons that completely fill its shells, it becomes exceptionally stable, further obstructing the fusion process.

Predicting Heavy Element Formation: The Importance of Energy Gaps

"For scientists trying to predict how heavy elements form, knowing the energy gap between unclear shells is critical—something that cannot be done without understanding the three-nucleon force." explains Fukui. "For magic number nuclei, this may require generating immense energy."

Quantum Entanglement of Nucleons: A Surprising Discovery

In their final discovery, the researchers identified another unexpected impact of the three-nucleon force on nucleon spins. With just the two-nucleon force, the spin states of each nucleon can be measured separately. However, the three-nucleon force induces quantum entanglement, where the spins of two of the three nucleons exist in both states simultaneously until observe.

Quantum Entanglement and Its Implications for Quantum Computing

"Similar to electrons, nucleons can exhibit quantum entanglement, although the greater mass of nucleons introduces distinct challenges. These variations could significant implications for future research, particularly in advancing technologies like quantum computing," concludes Fukui.

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