Collectivity evolution in the neutron-rich Pd isotopes towards the N=82 shell closure
H. Wang, N. Aoi, S. Takeuchi, M. Matsushita, P. Doornenbal, T. Motobayashi, D. Steppenbeck, K. Yoneda, H. Baba, L. Caceres, Zs. Dombradi, K. Kobayashi, Y. Kondo… 展开作者
H. Wang, N. Aoi, S. Takeuchi, M. Matsushita, P. Doornenbal, T. Motobayashi, D. Steppenbeck, K. Yoneda, H. Baba, L. Caceres, Zs. Dombradi, K. Kobayashi, Y. Kondo, J. Lee, K. Li, H. Liu, R. Minakata, D. Nishimura, H. Otsu, S. Sakaguchi, H. Sakurai, H. Scheit, D. Sohler, Y. Sun, Z. Tian, R. Tanaka, Y. Togano, Zs. Vajta, Z. Yang, T. Yamamoto, Y. Ye, R. Yokoyama
The neutron-rich, even-even 122,124,126Pd isotopes has been studied via in-beam gamma-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory. Excited states at 499(9), 590(11), and 686(17) keV were found in the three isotopes, which we assign to the respective 2+ -> 0+ decays. In addition, a candidate for the 4+ state at 1164(20) keV was observed in 122Pd. The resulting Ex(2+) systematics are essentially similar to those of the Xe (Z=54) isotopic chain and theoretical prediction by IBM-2, suggesting no serious shell quenching in the Pd isotopes in the vicinity of N=82.
Emerging collectivity and phase transition in mass A$\approx$150 region. New information for Nd isotopes
Faculty of Physics, University of Warsaw（华沙大学物理学院）；Department of Physics and Astronomy, The University of Manchester（曼彻斯特大学物理与天文学系）；Argonne National Laboratory（阿贡国家实验室）
The evolution of quadrupole and octupole collectivity in neutron-deficient Xe, Ba, Ce, and Nd nuclei near the "octupole magic" neutron number $N=56$ is investigated within the mapped $sdf$-IBM framework. Microscopic input is obtained via quadrupole and octupole constrained Hartree-Fock-Bogoliubov calculations, based on the parametrization D1M of the Gogny energy density functional. Octupole-deformed mean-field ground states are predicted for Ba and Ce isotopes near $N=56$. Excitation energies of positive- and negative-parity states as well as electric transition rates are computed with wave fu…
The emergence of nuclear collectivity near doubly-magic $^{132}$Sn was explored along the stable, even-even $^{124-130}$Te isotopes. Preliminary measurements of the $B(E2;4^{+}_{1}\rightarrow2^{+}_{1})$ transition strengths are reported from Coulomb excitation experiments primarily aimed at measuring the $g$ factors of the $4^{+}_{1}$ states. Isotopically enriched Te targets were excited by 198-205 MeV $^{58}$Ni beams. A comparison of transition strengths obtained is made to large-scale shell-model calculations with successes and limitations discussed.
Collectivity in the light Xenon isotopes: A shell model study
在相互作用壳模型（ISM）的框架下研究了最轻的氙同位素。价空间包括位于幻闭包N=Z=50和N=Z=82之间的所有轨道。计算产生的集体变形结构的三轴性质，包括很好地已知的实验数据。对N=Z核108- 108进行了预测（仍然未知）。结果解释为正宇称轨道的伪SU（3）结构增强的四极关联与0 h 11/2轨道引入的配对关联之间的竞争。我们还研究了100-Sn核的激发对我们预测的影响。我们表明，在这个区域中的回弯是由于在0 h 11/2轨道的两个粒子的对齐。在N=Z的情况下，一个中子和一个质子对准J=11和T=0。在110- 110和112- 110中，对准开始于J=10 T=1通道，并且它主要是中子中子型。接近能带终止时，一个中子和一个质子的排列变成J=11和T=0。我们以一种更学术的态度，探讨了等矢量和等密度配对关联对108-π和110-π的结构的作用，并研究了等矢量和等密度配对凝聚在这些N~Z核中的作用。
Enhanced octupole collectivity is expected in the neutron-deficient Ge, Se and Kr isotopes with neutron number $N \approx 40$ and has indeed been observed for $^{70,72}$Ge. Shape coexistence and configuration mixing are, however, a notorious challenge for theoretical models trying to reliably predict octupole collectivity in this mass region, which is known to feature rapid shape changes with changing nucleon number and spin of the system. To further investigate the microscopic configurations causing the prolate-oblate-triaxial shape transition at $A \approx 72$ and their influence on octupole…
Inelastic neutron scattering was used to study the low-lying nuclear structure of $^{132}$Xe. A comprehensive level scheme is presented, as well as new level lifetimes, multipole mixing ratios, branching ratios, and transition probabilities. Comparisons of these data as well as previously measured $E2$ strengths and $g$ factors are made with new shell-model calculations for $^{132,134,136}$Xe to explore the emergence of collectivity in the Xe isotopes with $N$ < 82 near the closed shell.
The onset of octupole deformation and its impact on related spectroscopic properties is studied in even-even neutron-rich lanthanide isotopes Xe, Ba, Ce, and Nd with neutron number $86\leqslant N\leqslant 94$. Microscopic input comes from the Hartree-Fock-Bogoliubov approximation with constrains on the axially symmetric quadrupole and octupole operators using the Gogny-D1M interaction. At the mean-field level, reflection asymmetric ground states are predicted for isotopes with neutron number around $N=88$. Spectroscopic properties are studied by diagonalizing the interacting boson model Hamilt…
The neutron-rich isotopes $^{58-63}$Cr were produced for the first time at the ISOLDE facility and their masses were measured with the ISOLTRAP spectrometer. The new values are up to 300 times more precise than those in the literature and indicate significantly different nuclear structure from the new mass-surface trend. A gradual onset of deformation is found in this proton and neutron mid-shell region, which is a gateway to the second island of inversion around \emph{N}=40. In addition to comparisons with density-functional theory and large-scale shell-model calculations, we present predicti…
Radioactive $^{129}$Sb, which can be treated as a proton plus semi-magic $^{128}$Sn core within the particle-core coupling scheme, was studied by Coulomb excitation. Reduced electric quadrupole transition probabilities, $B(E2)$, for the $2^+$ $\times$ $πg_{7/2}$ multiplet members and candidate $πd_{5/2}$ state were measured. The results indicate that the total electric quadrupole strength of $^{129}$Sb is a factor of 1.39(11) larger than the $^{128}$Sn core, which is in stark contrast to the expectations of the empirically successful particle-core coupling scheme. Shell-model calculations perf…
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…
Laser Spectroscopy of Thulium Isotopes Near the $N=82$ Shell Closure: Nuclear Moment and Charge Radius of ${}^{152\mathrm{m}}\mathrm{Tm}$
GSI Helmholtzzentrum für Schwerionenforschung GmbH（GSI亥姆霍兹重离子研究中心有限公司）；Helmholtz-Institut Mainz（美因茨亥姆霍兹研究所）；Johannes Gutenberg-Universität Mainz（约翰内斯·古腾堡大学美因茨分校）；Technische Universität Darmstadt（达姆施塔特工业大学）；KU Leuven（鲁汶大学）；Grand Accelerateur National d’Ions Lourds（法国国家大型重离子加速器研究所）
Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular for the determination of the appearance or disappearance of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti and V isotopes performed at the TITAN and LEBIT facilities. These measurements were made using the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were measured, eight of which represent increases in precision ove…
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 low-lying structure of neutron-rich odd-mass Kr isotopes is studied within the interacting boson-fermion model (IBFM) based on the Gogny-D1M energy density functional (EDF). The $(β,γ)$-deformation energy surfaces, spherical single-particle energies and occupation probabilities of the odd-mass systems are obtained using the constrained Hartree-Fock-Bogoliubov (HFB) approximation. Those quantities are used as a microscopic input to determine most of the parameters of the IBFM Hamiltonian. The remaining parameters are specifically tailored to the experimental spectrum for each of the studied…
We probe the $N=82$ nuclear shell closure by mass measurements of neutron-rich cadmium isotopes with the ISOLTRAP spectrometer at ISOLDE-CERN. The new mass of $^{132}$Cd offers the first value of the $N=82$, two-neutron shell gap below $Z=50$ and confirms the phenomenon of mutually enhanced magicity at $^{132}$Sn. Using the recently implemented phase-imaging ion-cyclotron-resonance method, the ordering of the low-lying isomers in $^{129}$Cd and their energies are determined. The new experimental findings are used to test large-scale shell-model, mean-field and beyond-mean-field calculations, a…
Evolution of high-spin states in neutron-rich $^{195-202}$Au isotopes approaching the $N=126$ shell closure
Seoul National University（首尔大学）；Institute for Basic Science（基础科学研究所）；Grand Accélérateur National d’Ions Lourds（大离子重离子加速器）；CEA/DRF-CNRS/IN2P3（法国原子能委员会/法国国家科学研究中心/法国国家核子和粒子物理研究所）；Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University（中山大学中法核工程与技术学院）
Rapid structural evolution of neutron-rich silicon isotopes toward N = 28
Facility for Rare Isotope Beams, Michigan State University（密歇根州立大学稀有同位素束设施）；Department of Physics and Astronomy, Louisiana State University（路易斯安那州立大学物理与天文系）；Department of Physics and Astronomy, Michigan State University（密歇根州立大学物理与天文系）；Advanced Science Research Center, Japan Atomic Energy Agency（日本原子能机构先进科学研究中心）；Center for Nuclear Study, University of Tokyo（东京大学核研究发展中心）；Center for Computational Sciences, University of Tsukuba（筑波大学计算科学中心）；Research Center for Nuclear Physics, Osaka University（大阪大学核物理研究中心）；KU Leuven, Instituut voor Kern- en Stralingsfysica（荷语鲁汶大学核与辐射物理研究所）
A precision mass investigation of the neutron-rich titanium isotopes $^{51-55}$Ti was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the $N=32$ shell closure and the overall uncertainties of the $^{52-55}$Ti mass values were significantly reduced. Our results confirm the existence of a weak shell effect at $N=32$, establishing the abrupt onset of this shell closure. Our data were compared with state-of-the-art \textit{ab-initio} shell model calculations which, despite very successfully describing where the $N=32$ shell gap is strong,…
New data on proton and neutron single-particle energies $E_{nlj}$ of Si isotopes with neutron number $N$ from 12 to 28 as well as occupation probabilities $N_{nlj}$ of single particle states of stable isotopes $^{28,30}$Si near the Fermi energy were obtained by the joint evaluation of the stripping and pick-up reaction data and excited state decay schemes of neighboring nuclei. The evaluated data indicate following features of single-particle structure evolution: persistence of $Z = 14$ subshell closure with $N$ increase, the new magicity of the number $N = 16$, and the conservation of the mag…
$β$-Decay Half-Lives Serve as Novel Evidence for the New Magic Number \(N=32\)
School of Nuclear Science and Technology, Lanzhou University（兰州大学核科学与技术学院）；Frontiers Science Center for Rare isotopes, Lanzhou University（兰州大学稀有同位素前沿科学中心）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；Department of Nuclear Physics, China Institute of Atomic Energy（中国原子能科学研究院核物理系）；School of Physics and Optoelectronic Engineering, Anhui University（安徽大学物理与光电工程学院）
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…
The masses of the exotic isotopes $^{210-214}$Ac and $^{210-214}$Ra have been measured with a multi-reflection time-of-flight mass spectrograph. These isotopes were obtained in flight as fusion-evaporation products behind the gas-filled recoil ion separator GARIS-II at RIKEN. The new direct mass measurements serve as an independent and direct benchmark for existing $α$-$γ$ spectroscopy data in this mass region. Further, new mass anchor points are set for U and Np nuclei close to the $N=126$ shell closure for a future benchmark of the $Z=92$ sub-shell for neutron-deficient heavy isotopes. Our m…
Mass measurements continue to provide invaluable information for elucidating nuclear structure and scenarios of astrophysical interest. The transition region between the $Z = 20$ and $28$ proton shell closures is particularly interesting due to the onset and evolution of nuclear deformation as nuclei become more neutron rich. This provides a critical testing ground for emerging ab-initio nuclear structure models. Here, we present high-precision mass measurements of neutron-rich chromium isotopes using the sensitive electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) …
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…
Structure of even-even Zr isotopes with 52$\leq$N$\leq$58 neutrons
Faculty of Physics, University of Warsaw（华沙大学物理学院）；Institut Laue-Langevin（朗之万研究所）；Grand Accélérateur National d’Ions Lourds (GANIL), CEA/DSM - CNRS/IN2P3（国家重离子加速器大装置（GANIL），CEA/DSM-CNRS/IN2P3）；INFN, Legnaro（意大利国家核物理研究所雷纳罗分部）
The first-excited state $g$~factor of $^{26}$Mg has been measured relative to the $g$ factor of the $^{24}$Mg($2^+_1$) state using the high-velocity transient-field technique, giving $g=+0.86\pm0.10$. This new measurement is in strong disagreement with the currently adopted value, but in agreement with the $sd$-shell model using the USDB interaction. The newly measured $g$ factor, along with $E(2^+_1)$ and $B(E2)$ systematics, signal the closure of the $νd_{5/2}$ subshell at $N=14$. The possibility that precise $g$-factor measurements may indicate the onset of neutron $pf$ admixtures in first-…
