145Er的β延发质子衰变性质研究

通过92Mo(58Ni, 2p3n)熔合蒸发反应生成了非常缺中子核145Er。利用氦喷嘴带传输系统把研究目标核传输到低本底测量站, 进行了质子 γ符合测量, 得到了不受同量异位素干扰的145Er的β延发质子谱。经过仔细分析与延发质子符合的γ谱, 发现了145Er的11/2-同核异能态具有β延发质子衰变性质。经拟合退激144Dy不同激发态γ跃迁的衰变曲线, 得出145Er的1/2+基态和11/2-同核异能态的半衰期分别为(1.6±0.6)和(0.6±0.1) s。最后, 简单介绍了中重质量区缺中子新核素的合成及衰变研究计划。The neutron deficient isotope 145Er was produced via the fusion evaporation reaction 92Mo(58Ni, 2p3n). The reaction products were transported to a low background counting area using a He jet tape transport system, and proton γ coincidence measurements were carried out. Based on the analysis of γ transitions in coincidence with β delayed protons, the β delayed proton decay of an νh11/2 isomer in 145Er was proposed. By fitting the decay curves of the γ transitions depopulating the low lying states in 144Dy, the half lives of the ground state and the νh11/2 isomeric state in 145Er were deduced to be (1.6±0.6) and (0.6±0.1) s, respectively. An experimental plan to synthesize new β delayed proton precursors in the medium heavy mass region has been presented.     

高自旋同质异能态束流的产生和应用

论述了高自旋同质异能态束流的物理意义.以RINKEN的HSIB为例,简略地叙述了高自旋同质异能态束流的产生、分离、传输及纯化的方法,并对高自旋同质异能态束流诱发核反应中放出的γ射线探测技术进行了论述. The physical motivations with high spin isomer beams were introduced. Taking HSIB of RIKEN as an example, the methods to produce, separate, transport and purify high spin isomer beams were described briefly, and the detection of γ rays emitted from the reactions induced by the high spin isomer beams was presented. Finally, the progress to develope the high spin isomers in the N =83 isotones as second beams was stressed.     

高自旋同质异能态束流及其在核谱学中的应用

介绍了在日本理化学研究所利用高自旋同质异能态束流装置上取得的核谱学研究结果。强调了可利用重离子核反应中逆运动学产生高自旋同质界能态束流,并用其进行二次核反应,描述了首次利用高自旋同质异能态束流完成的物理实验． The study of nuclear spectroscopy by using the High spin isomer Beam(HSIB)facility in RIKEN was introduced.The production of HSIB based on the inverse kinematics in heavy ion nuclear reaction,and its application for secondary nuclear reaction were stressed The first experimental result by using HSIB was also briefly discribed.     

176，178Os新低位激发态的识别

利用在束实验产生具有β^＋/EC衰变性质核素^176，178Ir，分析了在柬实验条件下获得的γ—γ符合数据，识别出了^176Os的4条新能级和13条新γ跃迁、^178Os的5条新能级和14条新γ跃迁。籍助氨喷嘴快速带传输系统，进一步对^176Ir的β’/EC衰变进行了测量，在确认在束测量新γ射线的同时建议了^176Ir的一个低自旋同核异能态。通过两准粒子耦舍的半经验计算，建议了^176，178Ir基态及同核异能态的组态。The γ rays following the β^＋/EC decay of ^176. 178Ir nuclei have been investigated using in-beam γ- ray experiment. A total of 4 new levels, 13 new γ transitions of ^176Os and 5 new levels, 14 new γ transitions of ^178Os were identified. In addition, with the aid of a helium-jet recoil fast tape transport system, the β^＋/EC decay of ^176Ir was further studied, the above new γ rays were proved and an isomer was proposed in ^176Ir. By the semiempirical calculations of two-quasiparticle intrinsic states of odd-odd nuclei, the configurations of ground states and isomeric states were also proposed for ^176, 178Ir     

Properties of the β-Delayed Proton Decay of 147Er

The β-delayed proton decay of 147Er is studied experimentally using the 58 Ni＋92Mo reaction at a beam energy of 383 MeV. Based on a He-jet apparatus coupled with a tape transport system, the β-delayed proton radioactivities both from the vδl/2 ground state and the vh11/2 isomer in 147 Er are identified by proton-7 coincidence measurements. By analyzing the time distribution of the 4＋ → 2＋-γ transition in the grand-daughter nucleus 146Dy, a half-life of 1.6 ± 0.2s is determined for the Vh11/2 isomer in 147 Er. The half-life for the ground state of 147Er is estimated to be 3.2±1.2 s.     

137Eu衰变的在线测量

使用在线同位素分离器及快带传输系统研究了缺中子稀土核137Eu的衰变性质,测量了A＝137核的γ、X单谱及γ-X、γ-γ符合谱,得到了137Eu核的半衰期为9．8s,并观测到了137Eu的一条能量为209．0keV的衰变γ线． The decay properties of neutron-deficient rare earth nucleus 137Eu have been studied by means of on-line isotope separator combined with rapid tape transport system.The products were produced by 190 MeV 36Ar bombarding on Pd target via natPd (36Ar, pxn)137Eu reactions. γ, X singles and γ-X, γ-γ coincidence spectra of the nuclei with A=137 were measured. The half-life of 137Eu is obtained to be 9. 8 s. A γ-ray with energy of 209. 0 keV for 137Eu was observed.     

20Mgβ衰变谱学与15O(α,γ)19Ne反应(英文)

15O（α,γ）19Ne（p,γ）20Na反应链是高温CNO循环向快速质子俘获过程突破的一条关键路径,相关的反应率输入量可通过20Mg的β衰变可布居19Ne共振态并测量其衰变性质来获得。通过高效率高精度地测量20Mg β衰变中产生的质子与γ射线得到了20Mg衰变的详细信息,并构建了完整的衰变纲图,还进行了19Ne 4 033 keV共振态衰变性质的探索,获得了该态在20Mg β衰变中被布居的分支比上限。通过比20Mg和20O镜像能级跃迁的结果确认了同位旋非对称性,为检验相关理论模型提供了精确的实验数据。对于突破路径中有重要影响的19Ne 4 033 keV共振态的性质,有待更高统计的实验进一步研究。The breakout from the hot CNO cycle to the rapid proton capture process can occur via the 15O(α,γ)19Ne(p,γ)20Na reaction sequence, and the β decay of 20Mg can be used as an alternative method to characterize some specific resonances, which will provide detailed nuclear structure input for reaction rate calculations. The reliable information on the decay properties and structure of 20Mg was obtained by measuring the emitted particles and γ-rays in the β decay with high efficiency and high resolution. Attempt was also made to search for the decay channels associated with the 4 033 keV resonance in 19Ne. To test fundamental symmetries, the transitions in the mirror decays of 20Mg and 20O were compared. The precise experimental data presented here would be important to constrain the theoretical calculations. It is desirable to clarify the astrophysically relevant problem by further experiments with improved statistics on the basis of the present work.     

Half-life of bismuth isotopes predicted by the Coulomb and proximity potential model; a proposition for the spherical nuclei

We know that the ground state energy, half-life, spin and parity of the heavy nuclei can be determined via the study of alpha decay. Bearing this in mind, we have calculated the penetration probability in the barrier, the decay constant and thereby the half-lives of 21 isotopes of Bi by using the proximity potential model. The comparison with the existing data is motivating.     

混合对称态对Majorana相互作用的依赖性(英文)

在 IBM2中研究了混合对称态 .发现某些较高自旋的混合对称态随着 Majorana相互作用很快变化 .这个结果改变了传统的关于混合对称态的观点 :最大 F旋态的能量最低 ,F旋越小 ,能量越高 .Fmin或 Fmin- 1的态会成为 yrast或 yrare态 .这些态很难向下衰变 ,因而很稳定.这个研究的结果表明可能存在一种由于质子和中子自由度的特殊性质而引起的新的同质异能态. Mixed symmetry states were studied in the framework of the neutron proton interacting boson model(IBM2). It was found that some of the mixed symmetry states with moderate high spins changed very fast with respect to the Majorana interaction. This changes our traditional picture that the maximum F spin states are the lowest in energy, the smaller the F spin, the higher the energy. The minimum F spin states or the state with F spin next to minimum may become the yrast or...     

Ir β+/EC衰变及其系统性分析

在在束实验条件下用γ-γ符合方法研究了具有β⁺/EC衰变性质的核素^176,178Ir的衰变γ射线. 另外借助氦喷嘴快速带传输系统在排除在束干扰的条件下, 进一步对¹⁷⁶Ir的β⁺/EC衰变进行了研究, 在确认在束测量新γ射线的同时建议了¹⁷⁶Ir的一个低自旋同核异能态. 从衰变系统性方面对^176,178Ir核中存在同核异能态的合理性和可能性进行了分析.     

在线同位素分离器和丰中子核β衰变

简要介绍了在线同位素分离器的原理以及在奇异核β衰变核谱学中的应用。着重介绍了芬兰Jyv（ae）skyl（ae）大学的离子制导型在线同位素分离器,并对在该装置上开展的丰中子Ag同位素的β^-衰变研究进行了综述。Isotope Separator on Line is briefly introduced with emphasis on the basic concept and features related to the production of exotic nuclei and β decay spectroscopy. The Ion Guide Isotope Separator on Line （IGISOL）at the University of Jyv（ae）skyl（ae）, Finland is presented in detail with experimental results on the decay of neutron-rich silver isotopes produced in proton induced symmetric fission.     

Nuclear structure and decay modes of Ra isotopes within an axially deformed relativistic mean field model

We examine the structural properties and half-life decay of Ra isotopes within the axially deformed Relativistic Mean-Field(RMF)theory with NL3 force parameters.We work out the binding energy(BE),RMS radii,two-neutron separation energies(S_(2n)),and some other observables.The results are in good agreement with the finite-range droplet model(FRDM)and experimental results.Considering the possibility of neutron magic number,theα-decay and cluster decay half-lives of Ra isotopes are calculated systematically using the Q-values obtained from the RMF formalism.These decay half-life calculations are carried out by taking three different empirical formulae.The calculated decay half-lives are found to be highly sensitive to the choice of Q-values.Possible shell or sub-shell closures are found at daughter nuclei with N=128 and N=126 when alpha and~8Be,~(12)C,~(18)O respectively are emitted from Ra isotopes.Though the cluster radioactivity is affected by the shell closure of parent and daughter,a long half-life indicates the stability of the parent,and a small parent half-life indicates that the shell stability of the daughter against decay.     

原子核基态双质子衰变的研究进展

基态双质子衰变是质子滴线区原子核的一种奇异衰变。 它可以揭示质子滴线区原子核外层质子对的结构行为, 检验现有核模型理论应用于极端条件下原子核的正确性。 搜索基态双质子衰变是人们广泛关注的一个实验难题, 直到理论预言提出后40多年才取得明显进展。 简要介绍了这一研究的进展情况。 The ground-state two-proton decay is an exotic decay beyond proton drip line. It deals with the structure behavior of the proton pair at outside orbital in a proton drip line nucleus, and can be used to check the current nuclear model under extreme condition. Experimental observation of ground state two proton decay has been widely considered as a challenge because of very low production cross section. In this short paper, the breakthrough of searching ground state two proton decay is briefly reviewed, which was made more than 40 years after the early theoretical prediction was proposed.     

超重核294118和291116及其α衰变链上各核素半衰期的研究

运用推广的液滴模型（GLDM）确定了超重核294118和291116及其α衰变链上各核素的衰变势垒, 采用量子力学中的WKB方法计算α衰变中的势垒穿透几率, 对该链上各原子核的α衰变半衰期进行了研究。 此外, 还利用Royer公式对该链上各原子核的α衰变半衰期进行了计算。 结果表明, GLDM 考虑亲和能与Royer公式给出的α衰变半衰期与超重核区的实验值符合很好, 验证了GLDM和Royer公式在超重核区的适用性,可以用来预测超重核的半衰期。 最后, 预言了Z=118 和116 同位素链上各核素的半衰期, 结果表明, 在Z=118和116中存在α衰变长寿命同位素, 这需要实验上的检验。The α decay potential barrier of the newly synthesized superheavy nuclei starting from 294118 and 291116 have been determined and their half lives have been studied with the Generalized Liquid Drop Model(GLDM) connected with WKB approximation and Royer’s formulae．The α decay half lives of the nuclei belonging to the superheavy nuclei starting from 294118 and 291116 have been calculated．The calculated results are in agreement with the experimental data, which show that the α decay half lives of superheavy nuclei with the GLDM and Royer’s formulae can be applied in the studying on superheavy nuclei successfully．Finally, the half lives of Z=118 and 116 isotopes have been predicted, and the results suggest there may be some long lived superheavy nuclei for α decay in those isotopes.     

远离稳定线核研究进展

近几年在对远离核的实验研究中,观测到了理论预言的新衰变模式,如45Fe的双质子衰变,β-缓发裂变;对中子滴线外一些核的存在可能性也进行了较多的实验探索和理论分析;开始了对人们一直关注的中子集团存在可能性的实验探索.远离核谱学和衰变性质研究逐渐深入,通过对一些远离核第一激发态能量的系统比较和许多远离核β衰变Q值的测量,以及核质量的精确测量,发现在远离核区,原有的一些幻数消失,代之产生了一些新的幻数,对其产生原因的理论分析做了简要的综述. Recently the predicted new decay model, for instance two-proton decay and β~(-)delayed fission have been observed in the investigations of the nuclei far from stability line. The existence of the nuclei located beyond the drip-line has already been studied experimentally and theoretically. It has been started to search for the neutron cluster in experiment by using neutron-rich nuclei. The researches of the spectroscopy and decay properties of the nuclei far from stability line are more and deeper, and...     

A=135核区N=79的同中异位素高自旋结构研究

摘要: 对清华大学在束γ谱实验组近年来在A=135缺中子核区N=79的同中异位素 135Ba, 137Ce和 139Nd的高自旋态实验研究进行了介绍。 实验是在中国原子能科学研究院HI 13串列加速器上用在束γ的实验技术、 分别通过重离子核反应 130Te(9Be, 4n), 124Sn(18O, 5n), 128Te(16O, 5n)进行的。 实验结果扩展了这3个核的高自旋态能级纲图。 研究表明, 这3个核的低自旋态结构均起源于 νh-111/2空穴与其偶偶核芯的耦合。 用粒子 转子模型对其结构进行了计算, 得到这3个核的形变参量γ值均稍大于30°, 为偏向于扁椭的三轴形变, 从而可看出Ba, Ce和Nd 3个同位素链在低自旋态下由长椭边到扁椭边的形状转变都发生在中子数N=77—79之间。 对于中等自旋态下一些能级的组态进行了指定与系统学比较。 在高自旋态下, 在 137Ce中发现一条γ≈－60°的扁椭形变带, 在 139Nd中则发现3条这样的扁椭形变带, 对这些扁椭形变带的起源及结构特性进行了讨论。 The progress of research on the high spin states at N=79 isotopes 135Ba, 137Ce and 139Nd in A=135 neutron deficient region by the research group of Tsinghua University has been reviewed. The experiments were carried out by using in beam γ ray spectroscopy technology and heavy ion nuclear reactions 130Te(9Be, 4n), 124Sn(18O, 5n) and 128Te(16O, 5n) at China Institute of Atomic Energy (CIAE). The high spin level schemes of these nuclei have been expanded. The results indicate that the lower spin states of these nuclei originated from νh-111/2 hole state coupling with the neighboring even even nucleus cores. All the deformation parameters γ values of these three isotones are larger than 30°, which indicates that they have triaxial deformation with oblate side. The prolate oblate transition in Ba, Ce and Nd isotopic chains indeed happens between N=77 and N=79. Through systematical comparison with the neighboring isotones, the configurations for some middle spin state levels have been assigned. At the high spin states, one oblate band in 137Ce and three ones in 139Nd with γ≈ -60° were discovered. The origination and structural character of these oblate bands have been discussed.     

矢量介子的辐射衰变

介子的辐射衰变是低能强子物理研究的重要方向, 通过它能够揭示介子的结构和性质。从有效场论的观点来看,介子衰变主要包含光子和强子之间的相互作用。使用SU(3)对称性和VMD模型分别对矢量介子的辐射衰变进行了研究。 通过对实验数据进行拟和,给出了在两种情形下V→Pγ的衰变宽度的理论值,并得到赝标量混合角θP 为－6°。 Radiative decay of mesons is an important aspect in low energy hadronic physics,through which structures and properties of mesons can be revealed. In view of effective field theories, the radiative decay of mesons involves mainly interactions between photons and hadrons. In this paper,we investigate the decay of vector mesons by using SU(3) symmetry and the vector meson dominance model respectively. By fitting with experiments, we give the theoretic widths for V→Pγ in both cases and the mixing angle of pseudoscalars θP is －6°.     

160Tb β-衰变纲图研究

对由160Tb的β-衰变而产生的γ射线利用GeLi和HpGe探测器进行了单谱和γ γ符合谱的测量.根据单谱和γ-γ符合谱的测量结果给出了160Tb的β-衰变纲图.并用绝热对称转动模型对160Dy中转动带与振动带的耦合参数Zγ值进行了计算,得出从振动带到转动带的γ跃迁几率B(E2)值之比不能通过唯一的Zγ值来描述.Tb/β-衰变;衰变纲图;带耦合参数 The γtransitions in 160Tb decay has been studied by γ ray spectroscopy and γ γ coincidence measurements with high efficiency Ge(Li) and HpGe detectors. The β- decay scheme of 160Tb was proposed according to the results of γ ray spectroscopy and γ γ coincidence measurement. The band mixing parameter Zγ for 160Dy is determined and it is observed that the measured γ ray branching ratios do not lead to a unique value of Zγ for 160 Dy.     

Triaxiality of High-K Isomers in A~130 Region

Remarkable triaxiality is found in the high-K isomeric states of A-130 nuclei using the configuration-constrained calculations of potential-energy surfaces. The triaxiality gives the further understanding of the decay properties of the isomers. The calculation with triaxiality can well explain the measured quadrupole moment of the K^z=7^- isomer in ^130Ce.     

准幻核中的近似广义辛弱数守恒（英文）

对称性在了解诸如原子核的转动、自旋和宇称、及同位旋等核结构性质中都起着重要的作用,并且使复杂的原子核结构问题得以简化。辛弱数就是由于原子核的对相互作用中的对称性所导出的众所周知的好量子数。通过对丰中子和缺中子核素及核素的高自旋态的衰变数据分析来揭示辛弱数的近似守恒性质。研究结果表明,在准幻核的高自旋同质异能素链中,无论所涉及的价空间的核子轨道有何不同,广义辛弱数总是近似的好量子数。Symmetry plays an important role in understanding the nuclear structure properties from the rotation of a nucleus to the spin, parity and isospin of nuclear states. This simplifies the complexity of the nuclear problems in one way or the other. Seniority is also a well known quantum number which arises due to the symmetry in the pairing interaction of nuclei. We present empirical as well as theoretical evidences based on decay rates which support the goodness of seniority at higher spins as well as in nrich or, n-deficient nuclei. We find that the generalized seniority governs the identical trends of high-spin isomers in different semi-magic chains, where different set of nucleon orbitals from different valence spaces are involved.