Estimating Magic Numbers Larger Than 126 by Fermi—Yang Liming Method

The Fermi-Yang Liming method is followed and developed to estimate new magic numbers in nuclei with a Woods-Saxon density function.The calculated results predict that the magic number next to 126 should be around 184 and 258.     

α particle preformation and shell effect for heavy and superheavy nuclei

The α particle preformation factor is extracted within a generalized liquid drop model for Z = 84-92 isotopes and N = 126,128,152,162,176,184 isotones.The calculated results show clearly that the shell effects play a key role in α particle preformation.The closer the proton and neutron numbers are to the magic numbers,the more difficult the formation of the α cluster inside the mother nucleus is.The preformation factors of the isotopes reflect that N = 126 is a magic number for Po,Rn,Ra,and Th isotopes,but for U isotopes the weakening of the influence of the N =126 shell closure is evident.The trend of the factors for N = 126 and N = 128 isotones also support this conclusion.We extend the calculations for N = 152,162,176,184 isotones to explore the magic numbers for heavy and superheavy nuclei,which are probably present near Z = 108 to N = 152,162 isotones and Z = 116 to N = 176,184 isotones.The results also show that another subshell closure may exist after Z = 124 in the superheavy nuclei.This is useful for future experiments.     

Stability of super heavy nuclei associated with the updated nuclear data

The stability of super heavy nuclei(SHN) from Z =104 to Z =126 is analyzed systematically,associated with the following theoretical mass tables: FRDM2012 [At.Data Nucl.Data Tables 109-110(2016)],WS2010 [Phys.Rev.C 82,044304(2010)],WS-LZ-RBF [J.Phys.G: Nucl.Part.Phys.42,095107(2015)] and the updated experimental data AME2016 [Chinese Physics C 41,040002(2017)].The nucleus with the biggest mean binding energy in each isotopic chain shows systematic regular behavior,indicating that the mean binding energy is a good criterion to classify SHN by their stability.Based on binding energy,the α-decay energy Q_α,two-proton separation energy S_(2p),and two-neutron separation energy S_(2n) are extracted and analyzed.It is found that N =152 and N =162 are sub-magic numbers,N = 184 is a neutron magic number,and Z = 114 is a proton magic number,which may provide useful information for the synthesis and identification of SHN.     

Generalization of α-Decay Cluster-Model to Nuclei Near Spherical and Deformed Shell Closures

The cluster model of α-decay is extended to the regions around doubly magic spherical nucleus 208pb and around deformed shell closure 270Hs, respectively. The effects of spherical shell closures (N = 126 and Z = 82) on α-decay are investigated by introducing an N-dependent α-preformation factor and a Z-dependent one inspired by a microscopic model. Good agreement between the theoretical α-decay half-lives and the measured ones is obtained for the spherical nuclei near the doubly magic nucleus 208 Pb, where the nuclear shell effect is included in the expression of α-preformation factor. The cluster model is also generalized for the decay of deformed nuclei. The branching ratios of a-decays from the ground state of a parent nucleus to the ground state (0 ) of its deformed daughter nucleus and to the first excited state (2 ) are .calculated in the framework of the cluster model. The results indicate that a measurement of c spectroscopy is a feasible method to extract the information of nuclear deformation of superheavy nuclei around the deformed nucleus 270 Hs.     

α preformation and penetration probability for heavy nuclei

The α preformation factor and penetration probability have been analyzed for even--even nuclei of Po, Rn, Ra using experimental released energies and α decay half-lives in the frame of the double folding model. It is shown that N=126 is a neutron magic number from α preformation and shell effects play an important role in α preformation. The closer the nucleon number is to the magic number, the more difficult α formation in the parent nucleus is. The preformation factor can supply information on the nuclear structure and the penetration probability mainly determines α decay half-life.     

Theoretical Study on N = 126 Shell Evolution

The nuclei around magic number N = 126 are investigated in the deformed relativistic mean field （RMF） model with effective interactions TMA. We focus investigations on the N = 126 isotonic chain. The N = 126 shell evolution is studied by analyzing the variations of two-neutron （proton） separation energies, quadruple deformations, single particle levels etc. The good agreement of two-neutron separation energies between experimental data and calculated values is reached. The RMF theory predicts that the sizes of N = 126 shell become smaller and smaller with the increasing of proton number Z. However, the N = 126 shell exists in our calculated region all along. According to the calculated two-proton separation energies, the RMF theory suggests ^220Pu is a two-proton drip-line nucleus in the N = 126 isotonic chain.     

Double folding analysis of 3He elastic and inelastic scattering to low lying states on 90Zr,116Sn and 208Pb at 270 MeV

The experimental data on elastic and inelastic scattering of 270 MeV³ He particles to several low lying states in⁹⁰Zr,¹¹⁶Sn and²⁰⁸Pb are analyzed within the double folding model（DFM）. Fermi density distribution（FDD） of target nuclei is used to obtain real potentials with different powers. DF results are introduced into a modified DWUCK4 code to calculate the elastic and inelastic scattering cross sections. Two choices of potentials form factors are used; Woods Saxon（WS） and Woods Saxon Squared（WS²） for real potential, while the imaginary part is taken as phenomenological Woods Saxon（PWS） and phenomenological Woods Saxon Squared（PWS²）. This comparison provides information about the similarities and differences of the models used in calculations.     

Generalization of α-Decay Cluster-Model to Nuclei Near Spherical and Deformed Shell Closures

The cluster model of a-decay is extended to the regions around doubly magic spherical nucleus ^208Pb and around deformed shell closure ^270Hs, respectively. The effects of spherical shell closures (N=126 and Z=82) on α-decay are investigated by introducing an N-dependent α-preformation factor and a Z-dependent one inspired by a microscopic model. Good agreement between the theoretical a-decay half-lives and the measured ones is obtained for the spherical nuclei near the doubly magic nucleus ^208Pb, where the nuclear shell effect is included in the expression of α-preformation factor. The cluster model is also generalized for the decay of deformed nuclei. The branching ratios of α-decays from the ground state of a parent nucleus to the ground state (0^ ) of its deformed daughter nucleus and to the first excited state (2^ ) are calculated in the framework of the cluster model. The results indicate that a measurement of α spectroscopy is a feasible method to extract the information of nuclear deformation of superheavy nuclei around the deformed nucleus ^270Hs.     

Alpha Decay,Shell Structure,and New Elements

We systematically analyze the experimental data of alpha decay in even-even heavy nuclei far from stability and find that the Geiger-Nuttall law brea~s for an isotopic chain when its neutron number is across a marc number or there is a deformed subshell. This break can be used to identify new magic numbers of superheavy nuclei. It is also discovered that there is a new linear relation between the logarithm of half-life and the reciprocal of the square root of decay energy for N = 126 and N = 152 isotones. It could be a new law of alpha decay for nuclei with magic neutron numbers but the physics behind it is to be explored. The significance of these researches for the search of new elements is discussed.     

Magic wavelengths for the 7s_(1/2)6d_(3/2,5/2)transitions in Ra~+

The dynamic polarizabilities of the 7s and 6d states of Ra~+are calculated using a relativistic core polarization potential method.The magic wavelengths of the 7s_(1/2)–6d_(3/2,5/2)transitions are identified.Comparing to the common radiofrequency(RF) ion traps,using the laser field at the magic wavelength to trap the ion could suppress the frequency uncertainty caused by the micromotion of the ion,and would not affect the transition frequency measurements.The heating rates of the ion and the powers of the laser for the ion trapping are estimated,which would benefit the possible precision measurements based on all-optical trapped Ra+.     

A Design of Magic Tee with Coplanar Arms

Magic tee is a widely used component in microwave systems; the four arms of conventional magic tee direct at four different directions, which give inconveniences to the assemblage of a system. In this paper, a broad-wall slot directional coupler and an E-plane dielectric loaded waveguide phase shifter is used to form a magic tee with four arms in the same E-plane. The magic tee is analyzed exactly with mode match method; and the simulated annealing method is used to optimize the performance of the magic tee. Simulation results are presented, which show good performance.     

用相对论平均场理论研究近滴线区原子核传统幻数的消失和新幻数的产生

提出了一种从理论上检验壳效应的方法.在考虑了由Bardeen，Cooper和Schrieffer提出的金属超导理论(BCS方法)的相对论平均场理论框架内，通过计算粒子数的涨落，发现涨落的大小和核的壳结构有紧密的关系，进而研究了滴线区一些传统幻数的消失和新幻数的产生. 关键词： 相对论平均场理论 粒子数涨落 幻数 壳效应     

Diffraction of neutral helium clusters: evidence for "magic numbers"

The size distributions of neutral 4He clusters in cryogenic jet beams, analyzed by diffraction from a 100 nm period transmission grating, reveal magic numbers at N=10-11, 14, 22, 26-27, and 44 atoms. Whereas magic numbers in nuclei and clusters are attributed to enhanced stabilities, this is not expected for quantum fluid He clusters on the basis of numerous calculations. These magic numbers occur at threshold sizes for which the quantized excitations calculated with the diffusion Monte Carlo method are stabilized, thereby providing the first experimental confirmation for the energy levels of 4He clusters.     

质子化学位移各向异性的测量

测量质子化学位移各向异性（CSA）有助于表征分子结构与其动力学,但由于¹H-¹H同核偶极耦合相互作用很强及质子各向异性化学位移较小,测量质子化学位移各向异性仍具有巨大挑战,特别是对含有多种质子的生物大分子,如蛋白质.本文简要综述了测量质子化学位移各向异性的方法,包括同核去耦慢速魔角旋转方法、超快魔角旋转方法、对称重耦（RN_n^v）方法、xCSA方法以及量子化学计算方法.我们重点介绍了在高速魔角旋转条件下蛋白质氨基质子化学位移各向异性的测量及它们与氢键长度、蛋白质二级结构之间的关系.     

量子盘三电子系统的基态性质

用少体物理的方法，研究了磁场中量子盘三电子系统极化态的基态能量和盘厚之间的关系.随着量子盘厚度的增加，三电子系统中的幻数角动量态即分数量子霍耳效应态将不再出现.结果还表明，幻数角动量消失的量子盘厚度随磁场强度的增加而减小. 关键词：     

Symmetric echo acquisition for absolute-value display in solid-state NMR imaging

A method of solid-state NMR imaging that permits echo Fourier transformation (FT) has been devised using a magic echo train. The echo FT imaging can be implemented simply by modifying the gradient pulse sequence in the previous magic echo imaging (TREV-16TS) so that the one-dimensional k-space trajectory follows the sampling points which are symmetric about the k origin. The implemented ability of echo FT improves the performance of the magic echo imaging: the sensitivity gained by radical2, the phase correction is made unnecessary, and the digital resolution is doubled. One- and two-dimensional imaging experiments have been conducted on some solid samples, confirming the improved performance and revealing a TREV-16TS adjustment parameter that is critical for the successful echo FT imaging.     

相对论平均场理论对Rn同位素链原子核基态性质的研究

在相对论平均场理论的框架下,对Rn同位素链原子核的结合能、形变、同位素位移等若干基态性质进行了较详细的研究.结果表明,理论计算结果与已有的实验数据符合较好.原子核的四极形变主要出现在远离幻数的区域(N=110-124和N=129-142).而在中子数大于幻数的区域(N=127-142),十六级形变也非常明显.对电荷半径的研究显示,Rn同位素链的同位素位移曲线的斜率在中子幻数处出现明显的变化. 关键词： 相对论平均场理论 电荷半径 同位素位移 单粒子能级     

Investigation of the shell structure of 40 ⩽ <Emphasis Type="Italic">A</Emphasis> ⩽ 132 magic and near-magic nuclei within the mean-field model involving a dispersive optical potential

Amethod for determining parameters of a dispersive optical potential is presented. This method is aimed at calculating single-particle energies of neutron and proton states of magic and near-magic nuclei. It is based on the use of global parameters of the imaginary part of the traditional-optical-model potential and experimental data on single-particle energies in the vicinity of the Fermi surface that were determined by simultaneously evaluating data on nucleon-stripping and nucleon-pickup reactions on the same nucleus. The potential of the method for describing and predicting single-particle energies of 40 ⩽ A ⩽ 132 magic and near-magic nuclei is demonstrated.     

H型魔幻态的纯化研究

魔幻态是解决容错量子计算的通用性的有力工具,因而高保真度魔幻态的获得是可靠的容错量子计算的一个重要问题.本文对H型魔幻态的纯化方案进行了数值模拟.该纯化方案基于7比特Steane码.我们的数值模拟结果显示该纯化方案对输入态围绕H轴的出错有一定容忍度.有趣的是,在H型魔幻态理论纯化阈值面下,我们发现一些量子态可以通过反复纯化,最终以较高的保真度接近H型魔幻态.