Evidence for prevalent Z = 6 magic number in neutron-rich carbon isotopes

Abstract

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 13–20C obtained from systematic analysis of point-proton distribution radii, electromagnetic transition rates and atomic masses of light nuclei. Performing ab initio calculations on 14,15C, 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.

Nuclear structure of Ni76 from the ( p,2p ) reaction

“…For larger neutron numbers the magicity of N = 28 was also proved to be soft; for example, in the 42 Si nucleus [8,9]. Regarding the protons, there are accumulating pieces of evidence for a new magic number at 6 in addition to 8 for neutron-rich carbon isotopes [10]. On the proton-rich side of the nuclear chart there were indications for a new magic number at 16 instead of 20 in the 28 S nucleus [11] as well.…”

Neutron quadrupole transition strength in C10 deduced from the C10(α,Furuno1, Kawabata2, Adachi3 et al. 2019Phys. Rev. CSelf Cite10020View full textAdd to dashboardCite

“…From the cross section of the α + 10 C inelastic scattering to the 2 + 1 state, the neutron transition matrix element of M n = 6.9 ± 0.7 (fit) ± 1.2 (sys) was obtained. The M n /M p ratio in 10 C was determined as M n /M p = 1.05 ± 0.11 (fit) ± 0.17 (sys), and thus the effect of the Z = 6 subshell closure reported in neutron-rich carbon isotopes [31] is not evident in the proton-rich side. This result is supported from the theoretical calculations.…”

“…In Ref. [31], the large M n /M p ratio or quenching of M p in neutron-rich carbon isotopes was attributed to the subshell closure at Z = 6. It is of interest to see whether the large M n /M p ratio is observed in a proton-rich carbon isotope as well, for example, 10 C.…”

Hypothetical Role of Large Nuclear Gravity in Understanding the Significance and Applications of the Strong Coupling Constant in the Light of Up and Down Quark Clusters

“…12) At 2 n  , quark cluster upper mass limit is 6 and at 3 n  , quark cluster upper mass limit is 14. See references [21,26].…”