Shell evolution in neutron-rich carbon isotopes: Unexpected enhanced role of neutron-neutron correlation

Abstract

Full shell-model diagonalization has been performed to study the structure of neutron-rich nuclei around ${}^{20}$C. We investigate in detail the roles played by the different monopole components of the effective interaction in the evolution of the N=14 shell in C, N and O isotopes. It is found that the relevant neutron-neutron monopole terms, $V_{d_{5/2}{d}_{5/2}}^{nn}$ and $V_{s_{1/2}{s}_{1/2}}^{nn}$, contribute significantly to the reduction of the N=14 shell gap in C and N isotopes in comparison with that in O isotopes. The origin of this unexpectedly large effect, which is comparable with (sometimes even larger than) that caused by the proton-neutron interaction, is related to the enhanced configuration mixing in those nuclei due to many-body correlations. Such a scheme is also supported by the large B(E2) value in the nucleus ${}^{20}$C which has been measured recently.

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• Shell evolution and its indication on the isospin dependence of the spin-orbit splitting
• The impact of the off-diagonal cross-shell interaction on ${}^{14}$C
• Recent progress in configuration-interaction shell model
• A simple formula for local burnup based on constant relative reaction rate per nuclei
• Quadrupole dynamics of carbon isotopes and 10Be
• Breakup effects in the ${}^{16}\mathrm{C}+p$ and ${}^{16}\mathrm{C}+d$ reactions
• Unbound states in 17C and p-sd shell-model interactions
• Configuration mixing effects in neutron-rich carbon isotopes
• Transport coefficients of dense nucleon matter at low temperature