近滴线核^{210,211}Ac 的高自旋态研究

Because of the low cross section and large fission probability, the traditional in-beam γ-ray spectroscopy technique can't be used to study the high-spin states of the proton-rich nuclei in the heavy nuclear region. However, the newly developed Recoil Decay Tagging (RDT) technique, which can select the reaction channel,is suitable for studying the high-spin level structure of the heavy proton-rich nuclei. The high-spin states of the near drip-line ^{210,211}Ac nuclei in the Z>82, N<126 region will be investigated on the Heavy Ion Research Facility in Lanzhou (HIRFL), using the RDT technique with a gas-filled recoil separator. In this project, the new level schemes in ^{210,211}Ac nuclei will be established, and some isomers will be searched and their lifetimes will be measured. In particular, according to the character of the level structure of ^{210,211}Ac nuclei, the experimental evidence of the onset of the deformation and collective motion will be sought, which will be used to check the theoretical prediction about the shape evolution and coexitence in the Ac isotopes. The theory, such as Cranked Shell Model, will be used to analyze the experimental results, discuss the microscopic origin of shape evolution and coexistence and isomers, and extract the information of the interaction between the valence nucleons and between the valence nucleon and the core in the Z>82, N<126 region.

传统的在束γ谱学技术受限于反应截面低、裂变截面大等原因，难以用来探索重核区质子滴线核的高自旋态。而新兴的反冲衰变标记（RDT）技术得益于反应道筛选方法，可以弥补传统技术的缺陷，实现对高本底、低截面下极端不稳定核素的高自旋态研究。本项目基于兰州重离子加速器，在充气反冲谱仪上运用RDT技术对Z>82，N<126核区近滴线核^{210,211}Ac的高自旋态进行研究，建立起全新的能级纲图,搜寻同质异能态并提取相应的能级寿命。根据^{210,211}Ac的能级结构特征，着重寻找原子核形变和集体运动的实验证据以验证理论预言的Ac同位素链的形状演化和共存。利用推转壳等理论模型对实验结果进行分析，研究形状共存和演化以及同质异能态的微观起源，提取该核区价核子之间，价核子与核芯之间相互作用的信息。

课题执行三年来，我们成功的完成了一套基于VME系统的多参数，高数据量的获取系统的研制。我们l利用180W(40Ar,4-5n)216,215U 熔合反应在国际上首次完成了215,216U新核素合成并测量了衰变寿命，并对相关alpha衰变技术进行了研究。利用充气谱仪，利用natSb(24Mg,3-4n)143-145Eu反应研究了143-145Eu的同质异能态衰变，并利用LaBr3探测器进行了相应的寿命测量，相关数据正在进一步的研究过程中。同时对104Ag，91,92Zr，190Pt的在束谱学进行了相应的研究，扩展或新建立了一些能级结构。