Shell-model studies of the N=14 and 16 shell closures in neutron-rich nuclei

Shell-model studies on the N =14 and 16 shell closures in neutron-rich Be, C, O and Ne isotopes are presented. We calculate, with the WBT interaction, the excited states in these nuclei. The calculations agree with recent experiment data. Excited energies and B(E2) values are displayed to discuss the shell closures. Our results support the N =16 shell closure in these isotopes, while indicating a disappearance of N =14 shell closure in Be and C isotopes.     

α-decay study of 218Ac and 221Th in 40Ar+186W reaction

In this study,²¹⁸Ac and ²²¹Th nuclides were produced via the heavy-ion induced fusion evaporation reaction ⁴⁰Ar+¹⁸⁶W.Their decay properties were studied with the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system.The cross section ratio between ²²²Pa and ²¹⁸Ac was extracted experimentally,withmeasured value 0.69(9).Two new possible α decay branches to ²²¹Th are suggested.The valence neutron configurations for the daughter ²¹⁷Ra are discussed in terms of the hindrance factors.     

Monopole effects,core excitations,and β decay in the A = 130 hole nuclei near ~(132)Sn

The proton and neutron cross-shell excitations across the Z = 50 shell are investigated in the southwest quadrant of ~(132) Sn by large-scale shell-model calculations with extended pairing and multipole-multipole force. The model space allows proton(neutron) core excitations, and both the low-and high-energy states for ~(130) In are well described, as found by comparison with the experimental data. The monopole effects between the proton orbit and neutron orbit are studied as the new monopole correction that perfectly reproduces the first 1~+ level in ~(130) In. The energy interval of proton(neutron) core excitations in ~(130) In lies in the range of 4.5-6.5(2.0-4.1) MeV, and the high energy yrast states are predicted as neutron core excitations. The decays are calculated among the A=130 nuclei of ~(130) In, ~(130) Sn and ~(130) Cd.     

Shell-model studies of the N=14 and 16 shell closures in neutron-rich nuclei

Shell-model studies on the N=14 and 16 shell closures in neutron-rich Be, C, O and Ne isotopes are presented. We calculate, with the WBT interaction, the excited states in these nuclei. The calculations agree with recent experiment data. Excited energies and B(E2) values are displayed to discuss the shell closures. Our results support the N=16 shell closure in these isotopes, while indicating a disappearance of N=14 shell closure in Be and C isotopes.     

基于核数据的中子诱发原子离位损伤截面评估方法

中子辐照损伤是核能系统面临的重要挑战之一。中子辐照损伤是由中子核反应诱发的，通常通过离位损伤(用平均每原子离位数DPA计)量化。离位损伤的过程为中子核反应产生的反冲核，在辐照损伤中称为初级碰撞原子(Primary Knock-on Atom,PKA)，引发材料中原子级联碰撞产生，因此其评估需要基于中子核反应理论或相关核数据。由于现有评价核数据库中未包含全部反冲能谱分布，中子辐照导致的离位损伤截面需要基于已有微分截面与守恒方程计算。本工作回顾了中子辐照诱发离位损伤的两种计算思路、系统地归纳了不同核反应类型(包括离散与连续的两体反应、中子俘获反应以及多体反应)导致的离位损伤截面计算理论方法、并指出了现有方法的不足。最后，以事故容错包壳材料FeCrAl为例，基于ENDF/B-Ⅷ.0数据库计算了多组不同Cr与Al含量的离位损伤截面。初步研究结果表明FeCrAl的中子辐照离位损伤评估对其中Cr与Al含量的敏感性较低且高出Fe单质的DPA截面约3%～4%，因此DPA评估中可暂不考虑不同Cr与Al含量的影响。但Cr与Al的含量可能会影响离位阈能与损伤能量。     

Alignments in the nobelium isotopes

Total-Routhian-Surface calculations have been performed to investigate the deformation and alignment properties of the No isotopes. It is found that normal deformed and superdeformed states in these nuclei can coexist at low excitation energies. In neutron-deficient No isotopes, the superdeformed shapes can even     

Fine structure ofαdecay in222Pa

With the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system,the fine structure of the α decay for²²²Pa was studied.The nuclides were produced through the 1p3n evaporation channel via the heavy-ion induced fusion evaporation reaction ⁴⁰Ar+¹⁸⁶W.Based on the ER-α1-α2-α3 andα-γcorrelation measurement,three new α decays were observed in addition to the three branches known previously.The one with the largestαdecay energy was regarded as the ground state to ground state transition.The newly measuredαdecay properties of ²²²Pa were examined in a framework of reduced width.     

哪些核适合被液滴模型描述:基于不确定度分解方法的统计研究（英文）

一个模型适合描述哪些物理量? 这个问题可以通过模型的物理来源来回答。比如,液滴模型适合描述重核和远离满壳核。这是因为液滴近似更适用于核子数多的核以及液滴模型不包含壳效应。这样的回答是定性的并需要清楚模型的物理来源。是否可能仅通过模型的数学形式和实验数据就能给出半定量的解答? 利用最近提出的不确定度分解方法尝试对液滴模型适合描述哪些核这一问题进行半定量的回答。并且不需已知液滴模型的物理来源,仅需其数学形式以及实验数据。通过不确定度分解方法,液滴模型与实验数据间的残差可以分解为系统不确定度和统计不确定度。两者分别代表了模型的缺陷和模型不精确的参数带来的不确定度。基于这一分解,核素图上的原子核可以按其对应的残差被半定量地划分为系统不确定度主导、统计不确定度主导、以及中间区域。液滴模型适合描述的核就是统计不确定度主导残差的核而不是像通常认为的是残差最小的核。从核素图上看,统计不确定度主导残差的核正是重核以及远离满壳核,与液滴模型物理来源一致,但得到这一结果的过程是半定量的且仅需液滴模型的数学形式以及实验数据。如果对由统计不确定度主导残差的核重新拟合液滴模型的参数,模型可以很好地描述这些核（标准差小于0.7 MeV）。Which data are well described by a theoretical model? Such questions can be answered through the physical origin of the model. For example, the liquid drop model (LDM) well describes the heavy and far from shell nuclei. Because the liquid-drop assumption is more suitable for nuclei with more nucleons and LDM does not include the shell effect. Such answer is qualitative and needs a clear view on the physical origin of the model. Is it possible to give an semi-quantitatively answer only from the mathematical form of the model and the observed data. In the present work, the recently suggested uncertainty decomposition method (UDM) is used to answer which nuclei are well described by LDM. The residues between LDM and the observed data can be decomposed through UDM to systematic and statistical uncertainties, which represent the uncertainty of the deficiency of the model and the indeterminate parameters, respectively. Based on UDM, the chart of nuclides are semi-quantitatively divided into three parts, areas dominated by the systematic and statistical uncertainties, and the cross area. Contrary to the common sense, the well described nuclei by LDM are not the nuclei with small residues, but actually the nuclei of which the residues are dominated by the statistical uncertainty. These nuclei are indeed the heavy and far from shell nuclei, which agrees with the physical consideration of LDM. But only the mathematical form of the model and the experimental data are needed during the use of UDM. The nuclides dominated by the statistical uncertainty can be well described by LDM (standard deviation less than 0.7 MeV) with parameters fitting to these nuclei.