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.

Research on High Spin Structures of N=79 Isotones in A=135 Nuclear Region

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.