Shell structure of $^{43}$S and collapse of the $N=28$ shell closure
S. Momiyama, K. Wimmer, D. Bazin, J. Belarge, P. Bender, B. Elman, A. Gade, K. W. Kemper, N. Kitamura, B. Longfellow, E. Lunderberg, M. Niikura, S. Ota, P. Schr… 展开作者
S. Momiyama, K. Wimmer, D. Bazin, J. Belarge, P. Bender, B. Elman, A. Gade, K. W. Kemper, N. Kitamura, B. Longfellow, E. Lunderberg, M. Niikura, S. Ota, P. Schrock, J. A. Tostevin, D. Weisshaar
The single-particle structure of the $N=27$ isotones provides insights into the shell evolution of neutron-rich nuclei from the doubly-magic $^{48}$Ca toward the drip line. $^{43}$S was studied employing the one-neutron knockout reaction from a radioactive $^{44}$S beam. Using a combination of prompt and delayed $γ$-ray spectroscopy the level structure of $^{43}$S was clarified. Momentum distributions were analyzed and allowed for spin and parity assignments. The deduced spectroscopic factors show that the $^{44}$S ground-state configuration has a strong intruder component. The results were confronted with shell model calculations using two effective interactions. General agreement was found between the calculations, but strong population of states originating from the removal of neutrons from the $2p_{3/2}$ orbital in the experiment indicates that the breakdown of the $N=28$ magic number is more rapid than the theoretical calculations suggest.
Magicity, or shell closure, plays an important role in our understanding of complex nuclear phenomena. In this work, we employ one of the state-of-the-art density functional theories, the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the density functional PC-PK1, to investigate the evolution of the $N=20,28,50$ shell closures in the $ 20 \leqslant Z \leqslant 30$ region. We show how these three conventional shell closures evolve from the proton drip line to the neutron drip line by studying the charge radii, two-neutron separation energies, two-neutron gaps, quadru…
We report high-precision mass measurements of $^{50-55}$Sc isotopes performed at the LEBIT facility at NSCL and at the TITAN facility at TRIUMF. Our results provide a substantial reduction of their uncertainties and indicate significant deviations, up to 0.7 MeV, from the previously recommended mass values for $^{53-55}$Sc. The results of this work provide an important update to the description of emerging closed-shell phenomena at neutron numbers $N=32$ and $N=34$ above proton-magic $Z=20$. In particular, they finally enable a complete and precise characterization of the trends in ground stat…
Level structure of light neutron-rich La isotopes beyond the N=82 shell closure
GANIL, CEA/DRF-CNRS/IN2P3（法国国家大加速器研究中心）；Shandong University（山东大学）；Weihai Research Institute of Industrial Technology of Shandong University（山东大学威海工业技术研究院）；Vanderbilt University（范德堡大学）；Variable Energy Cyclotron Centre（变能回旋加速器中心）；Homi Bhabha National Institute（霍米·巴巴国立研究所）；Sun Yat-sen University（中山大学）；Institute for Basic Science（基础科学研究院）；Université Paris-Saclay（巴黎萨克雷大学）；Institute of Nuclear Physics PAN（波兰科学院核物理研究所）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Université de Strasbourg（斯特拉斯堡大学）；Tata Institute of Fundamental Research（塔塔基础研究所）；Tsinghua University（清华大学）
The first investigation of the single-particle structure of the bound states of 17C, via the d(16C, p) transfer reaction, has been undertaken. The measured angular distributions confirm the spin-parity assignments of 1/2+ and 5/2+ for the excited states located at 217 and 335 keV, respectively. The spectroscopic factors deduced for these states exhibit a marked single-particle character, in agreement with shell model and particle-core model calculations, and combined with their near degeneracy in energy provide clear evidence for the absence of the N = 14 sub-shell closure. The very small spec…
Facility for Rare Isotope Beams, Michigan State University（稀有同位素束流设施，密歇根州立大学）；Physics Division, Oak Ridge National Laboratory（橡树岭国家实验室物理部）；Department of Physics and Astronomy, University of Tennessee（田纳西大学物理与天文学系）
Background: In neutron-rich nuclei neighboring 42Si, the quenching of the N = 28 shell gap occurs and is expected to induce the shape coexistence in their excitation spectra. Purpose: We show that different nuclear shapes coexist in N = 28 isotones 40Mg, 42Si, and 44S, and investigate observables to probe it. Method: Antisymmetrized molecular dynamics with Gogny D1S density functional is applied to describe the shape coexistence phenomena without ad hoc assumption of the nuclear shape. Results: We find that rigid shapes with different deformations coexist in the ground and the first excited 0+…
The strength of the $N$ = 28 magic number in neutron-rich argon isotopes is examined through high-precision mass measurements of $^{46-48}$Ar, performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The new mass values are up to 90 times more precise than previous measurements. While they suggest the persistence of the $N$ = 28 shell closure for argon, we show that this conclusion has to be nuanced in light of the wealth of spectroscopic data and theoretical investigations performed with the \emph{SDPF-U} phenomenological shell model interaction. Our results are also compared with \emph{…
The root mean square radii of the proton density distribution in $^{16-24}$O derived from measurements of charge changing cross sections with a carbon target at $\sim$900$A$ MeV together with the matter radii portray thick neutron skin for $^{22 - 24}$O despite $^{22,24}$O being doubly magic. Imprints of the shell closures at $N$ = 14 and 16 are reflected in local minima of their proton radii that provide evidence for the tensor interaction causing them. The radii agree with it ab initio calculations employing the chiral NNLO$_{\mathrm{sat}}$ interaction, though skin thickness predictions are …
Systematic study of $\boldsymbol{\mathcalα}$ decay of nuclei around $\boldsymbol{Z=82}$, $\boldsymbol{N=126}$ shell closure within the cluster-formation model and proximity potential 1977 formalism
本文系统地研究了团簇形成模型中的$\mathcalα$衰变预形成因子$P_α$，并利用邻近势1977方法研究了$Z=82$、$N=126$闭壳层周围原子核的$\mathcalα$衰变半衰期.计算结果表明，实际的$P_α$与价质子（空穴）和价中子（空穴）的乘积$N_pN_n$成线性关系。这与我们以前的工作[X.- D. Sun \textit{et al.}，\href{https://journals.aps.org/prc/abstract/10.1103/PhysRevC.94.024338}{ Phys. Rev. C 94, 024338 (2016)}，J.- G. Deng \textit{et al.}，\href{https://journals.aps.org/prc/abstract/10.1103/PhysRevC.96.024318}{Phys. Rev. C 96, 024318 (2017)} ]，其中$P_α$是模型依赖性的，并且从计算的$\mathcalα$半衰期与实验数据的比率中提取。结合我们以前的工作，我们证实了价质子-中子相互作用在$Z=82$周围的核的$\mathcalα$预形成中起着关键作用，无论$\mathcalα$是模型依赖的还是微观的，$N=126$壳层闭合.此外，我们计算的$\mathcalα$衰变半衰期，采用邻近势1977年的形式…
The mean-square charge radii of $^{207,208}$Hg ($Z=80, N=127,128$) have been studied for the first time and those of $^{202,203,206}$Hg ($N=122,123,126$) remeasured by the application of in-source resonance-ionization laser spectroscopy at ISOLDE (CERN). The characteristic \textit{kink} in the charge radii at the $N=126$ neutron shell closure has been revealed, providing the first information on its behavior below the $Z=82$ proton shell closure. A theoretical analysis has been performed within relativistic Hartree-Bogoliubov and non-relativistic Hartree-Fock-Bogoliubov approaches, considering…
r-Process Nucleosynthesis With Ab Initio Nuclear Masses Around The N=82 Shell Closure
Technische Universität Darmstadt（达姆施塔特工业大学）；Center for Computational Sciences, University of Tsukuba（筑波大学计算科学中心）；ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH（GSI重离子研究中心极端物质研究所EMMI）；Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）
Combining laser spectroscopy in a Versatile Arc Discharge and Laser Ion Source, with Penning-trap mass spectrometry at the CERN-ISOLDE facility, this work reports on mean-square charge radii of neutron-rich mercury isotopes across the $N = 126$ shell closure, the electromagnetic moments of $^{207}$Hg and more precise mass values of $^{206-208}$Hg. The odd-even staggering (OES) of the mean square charge radii and the kink at $N = 126$ are analyzed within the framework of covariant density functional theory (CDFT), with comparisons between different functionals to investigate the dependence of t…
