Research Center for Nuclear Physics, Osaka University, Osaka, 567-0047, Japan.
Institute of Physics, Vietnam Academy of Science and Technology, Hanoi, 10000, Vietnam.
Nat Commun. 2018 Apr 23;9(1):1594. doi: 10.1038/s41467-018-04024-y.
The nuclear shell structure, which originates in the nearly independent motion of nucleons in an average potential, provides an important guide for our understanding of nuclear structure and the underlying nuclear forces. Its most remarkable fingerprint is the existence of the so-called magic numbers of protons and neutrons associated with extra stability. Although the introduction of a phenomenological spin-orbit (SO) coupling force in 1949 helped in explaining the magic numbers, its origins are still open questions. Here, we present experimental evidence for the smallest SO-originated magic number (subshell closure) at the proton number six in C obtained from systematic analysis of point-proton distribution radii, electromagnetic transition rates and atomic masses of light nuclei. Performing ab initio calculations on C, we show that the observed proton distribution radii and subshell closure can be explained by the state-of-the-art nuclear theory with chiral nucleon-nucleon and three-nucleon forces, which are rooted in the quantum chromodynamics.
核壳结构源于核子在平均势中的近乎独立运动，为我们理解核结构和潜在的核力提供了重要线索。其最显著的特征是存在与额外稳定性相关的所谓质子和中子的“幻数”。尽管 1949 年引入了唯象的自旋轨道（SO）耦合力有助于解释幻数，但它们的起源仍然是悬而未决的问题。在这里，我们通过对轻核的质子分布半径、电磁跃迁率和原子质量的系统分析，提供了来自 C 中质子数为 6 的最小 SO 起源的幻数（子壳层闭合）的实验证据。我们对 C 进行了从头算计算，结果表明，观察到的质子分布半径和子壳层闭合可以用基于手征核子-核子和三体核力的最新核理论来解释，这些力源于量子色动力学。
