"Transformative Impacts of Neutron Migration: Advancing the Frontier in Nuclear Fusion"

Nuclear fusion reactions at low energies are impacted by nucleon migration and isospin compositions of nuclei. Studies highlight the role of nuclear shape and isospin dynamics in lowering the fusion barrier, which could advance nuclear physics and energy solutions. Credit: SciTechDaily.com

Low-energy nuclear fusion reactions are influenced by the migration of neutrons and protons between fusing nuclei and their isospin compositions. Research conducted using high-performance computational models has shown the importance of isospin dynamics and nuclear shapes, particularly in asymmetric, neutron-rich systems, revealing significant implications for nuclear physics and potential energy applications.

Low-energy nuclear fusion reactions can potentially provide clean energy. In stars, low-energy fusion reactions during the stages of carbon and oxygen burning are critical to stellar evolution. These reactions also offer valuable insights into the exotic processes occurring in the inner crust of neutron stars as they accumulate matter. However, scientists do not fully understand the underlying dynamics governing these reactions.

The key to unlocking the fusion process is understanding how nucleons move between the two fusing nuclei. As the nuclei draw close enough for the nuclear forces to become effective, neutrons and protons can migrate from one nucleus to another. This movement potentially eases the fusion process.

Shaded outlines of calcium-40 and ytterbium-176 nuclei (40Ca+176Yb) as they collide, leading to fusion, with nucleon currents for neutrons in blue and protons in red. The net neutron flow is from 176Yb to 40Ca and the proton flow is the opposite. Credit: Sait Umar

This study explored the influence on low-energy fusion processes of isospin composition. This is a key nuclear property that differentiates protons from neutrons. The researchers used computational techniques and theoretical modeling to investigate the fusion of different nuclei with varying isospin configurations. The results show that the isospin composition of the nuclei in a fusion reaction plays a crucial role in understanding the reaction.

The findings provide insights into the processes that govern low-energy fusion reactions. This could enhance scientific research on astrophysical processes such as nucleosynthesis, which is critical to our understanding of the universe as a whole.

In this study, researchers at Fisk University and Vanderbilt University used high-performance computational and theoretical modeling techniques to conduct a detailed many-body method study of how the dynamics of isospin influence nuclear fusion at low energies across a series of isotopes.

The study also examined how the shape of the nuclei involved affect these dynamics. In systems where the nuclei are not symmetrical, the dynamics of isospin become particularly important, often leading to a lowered fusion barrier, especially in systems rich in neutrons. This phenomenon can be explored using facilities that specialize in the generation of beams composed of exotic, unstable nuclei.

The findings provide critical knowledge regarding the fundamental nuclear processes governing these reactions, which have broad implications for fields such as nuclear physics, astrophysics, and, perhaps someday, fusion-based energy.

Reference: “Role of isospin composition in low-energy nuclear fusion” by Richard Gumbel, Christian Ross and A. S. Umar, 14 November 2023, Physical Review C. DOI: 10.1103/PhysRevC.108.L051602

This research was supported by the Department of Energy Office of Science, Office of Nuclear Physics.