Researchers from the Institute of Theoretical Physics at the Chinese Academy of Sciences have published a study in the journal Physical Review Letters that delves into the properties of atomic nuclei, specifically the neutron skin thickness in heavy, man-made elements known as transuranium elements. The team, comprising Peng Wang, Zi-Dan Huang, Shuang-Quan Zhang, and Ting-Ting Sun, has employed advanced theoretical models to better understand the behavior of neutrons in these complex nuclei.
The study focuses on the neutron skin thickness, a measure of how much the neutron distribution extends beyond the proton distribution in an atomic nucleus. This property is crucial for understanding the nuclear symmetry energy, which describes how the energy of a nucleus changes with the difference between the number of neutrons and protons. The researchers used the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) to systematically investigate the neutron skin thickness in the berkelium isotopic chain, which includes nuclei with the same number of protons but varying numbers of neutrons.
The results reveal that the neutron skin thickness generally increases with the number of neutrons, but exhibits notable decreases at specific points known as shell closures, where the nuclear shell structure is particularly stable. By breaking down the neutron skin thickness into volume and surface contributions, the researchers found that the volume term accounts for the majority of the neutron skin thickness in most nuclei, while the surface term becomes more significant near the proton drip line, where nuclei become unstable due to an excess of protons.
The study also examines the role of nuclear deformation, which slightly reduces the central radius of the nucleus but significantly enhances the surface diffuseness, leading to an increase in the neutron skin thickness driven largely by the surface term. Additionally, the researchers explored the anisotropy of the neutron skin thickness, finding that in prolate deformed nuclei, which are elongated along the symmetry axis, the neutron skin thickness is substantially larger in the perpendicular direction. This anisotropy is primarily attributed to the volume term, which remains the dominant contribution in most nuclei regardless of direction.
The findings provide new insights into the interplay between deformation, shell structure, and the neutron skin in finite nuclei, which could have implications for understanding the properties of neutron-rich matter and the behavior of matter under extreme conditions. While the direct practical applications to the energy sector may not be immediately apparent, a deeper understanding of nuclear structure and the behavior of neutrons can contribute to advancements in nuclear energy, including the development of more efficient and safer nuclear reactors, as well as the potential for new types of nuclear fuel.
This article is based on research available at arXiv.