230U重离子衰变的观测

利用35MeV的质子束轰击ThO₂粉末靶,通过²³²Th(p,3n)反应产生²³⁰Pa核,经用放射化学方法分离出²³⁰Pa核并制成²³⁰Pa→²³⁰U测量源.用聚乙烯对苯二酸酯固体核径迹探测器记录其发射的重离子径迹.经248天的收集,观测到了两个²³⁰U→²⁰⁸Ph+²²Ne衰变事件,相对于α衰变的分支比为(1.3±0.8)×10^－14.     

缺中子120Ba核EC/β+衰变的再研究

利用171MeV ³²S束轰击⁹²Mo靶,熔合蒸发(2n2p)反应合成了¹²⁰Ba核.由氦喷嘴反冲快速带传输系统将反应产物送到低本底区.位于带子两侧的两个平面型高纯锗探测器对反应产物进行了符合测量.经离线数据分析,对早先发表的¹²⁰Ba衰变γ射线予以确认,并补充了19条强度较弱、能量较低的γ射线.建议了¹²⁰Ba的衰变纲图共包括35条γ射线和25条能级.     

新重丰中子核237Th的合成和鉴别

用14MeV中子照射(NH₄)₂U₂O₇粉末,通过²³⁸U(n,2p)²³⁷Th反应产生了新的重丰中子同位素²³⁷Th,并用放射化学方法分离了它.借助于跟踪其子体²³⁷pa的γ射线的时间序列谱首次鉴别了这个新活性.利用递次衰变分析程序得到了²³⁷Th的半衰期为5.0±0.9min.另外,发现了一条能量为35.1±0.3keV T_1/2=5.0±1.1min的新γ射线并指定它为²³⁷Th衰变.     

EC/β+ decay of six medium-heavy nuclei

Previous experimental results of (EC+β⁺) decay for the medium-heavy nuclei reported by our group since 1996, including ¹⁵³Er, ¹⁵⁷Yb, ²⁰⁹Fr, ¹²⁸Ce, ¹³⁰Ce, and ¹²⁸Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion.     

实验测定183Os的QEC值

用39MeV-α粒子轰击天然钨靶产生了¹⁸³Os测量了¹⁸³Os衰变的γ-β符合谱,确定了β⁺能谱的端点能量.最终提取出 衰变的QQ_EC值:Q_EC=2.24±0.10MeV,与系统学的估计值;2.30±0.10MeV在误差范围内相符.     

合成和研究滴线区新核素β延发质子先驱核121Ce

利用³²S束轰击⁹²Mo靶,熔合蒸发3n反应合成了¹²¹Ce.藉助于具有γ(X)-p-t符合测量的氦喷嘴反冲快速带传输系统进行分离和鉴别.实验定出¹²¹)Ce的半衰期为(1.1±0.1)s,观测到了¹²¹Ce的延发质子谱并近似估计了延发质子分支比为(1.0±0.5)%.     

EC/β+ decay of six medium-heavy nuclei

Previous experimental results of (EC+β+) decay for the medium-heavy nuclei reported by our group since 1996, including 153Er, 157Yb, 209Fr, 128Ce, 130Ce, and 128Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion.     

89Ru的β缓发质子衰变性质

藉助氦喷嘴带传输系统,采用“p-γ”符合的鉴别原理,成功地合成与鉴别了⁵⁸Ni(³⁶Ar, 2p3n)反应产生的核素⁸⁹Ru,并研究了它的β缓发质子衰变性质.实验给出⁸⁹Ru的衰变半衰期为(1.2±0.2)s, 测定了它的β缓发质子能谱,提取出了⁸⁹Ru经缓发质子衰变布居到子核⁸⁸Mo的2⁺和4⁺态的相对终态分支比(100∶6).通过与统计模型计算结果进行对比,初步指定了⁸⁹Ru基态的自旋 宇称(5/2⁺或7/2^±)和质量过剩(-59.5 MeV).     

稀土区质子滴线附近新的β缓发质子衰变

用重离子束³⁵Ar轰击缺中子同位素靶⁹²Mo,⁹⁶Ru和¹⁰⁶Cd产生了质子滴线附近的β缓发质子先驱核¹²⁵Nd,¹²⁸Pm,¹²⁹Sm,¹³⁷Gd和¹³⁹Dy.配合氦喷嘴带传输系统用“p-γ”符合方法对它们进行了肯定的鉴别.它们的半衰期分别为：0.60(15)s,1.0(3)s,0.55(10)s,2.2(2)s和0.6(2)s.用统计模型理论计算对实验测定的¹²⁵Nd, ¹²⁹Sm,¹³⁷Gd和¹³⁹Dy的,和从前报道的¹²¹Ce,¹³⁵Gd的β缓发质子衰变的能谱和分支比进行了拟合.提取出¹²¹Ce, ¹²⁵Nd, ¹²⁹Sm,¹³⁵Gd, ¹³⁷Gd和¹³⁹Dy的基态自旋-宇称分别为5/2^±,5/2^±,1/2⁺(或3/2⁺),5/2⁺,7/2^±和7/2⁺.实验初步指认的基态自旋 宇称值与Nilsson能级图的预言值相符间接表明这6种核素的基态具有大形变,形变参数β₂在0.3左右.     

β-delayed proton decay of the proton drip-line nucleus 142Ho in the rare-earth region

New β-delayed proton precursor 142Ho was produced via heavy ion induced reaction 106Cd(40Ca, p3n), and identified for the first time by using a He-jet fast tape transport system in combination with "p-γ" coincidence measurements. The β-delayed proton decay of 142Ho was observed and its half life was determined to be (0.4±0.1) s. By fitting the experimental relative branching ratios to final states in the proton daughter nucleus 141Tb and the energy spectrum of β-delayed protons with a statistical model calculation, the ground-state spin of 142Ho was assigned as 5, 6 or 7. Nuclear energy-potential-surface (EPS) calculations were performed using the Woods-Saxon Strutinsky method. The calculated results favored the assignments of 7- to 142Ho. AS the by-products, some γ-transitions in the proton daughter nuclei following the β-delayed proton decays of precursors 139Gd, 140Tb, 142Tb, and 143Dy were reported here for the first time.