近质子滴线核150,151Tm的多准粒子激发特性研究

With the new Gas-filled Recoil Separator at Lanzhou being finished, it opens excellent opportunities for the study of nuclear structure with nuclei along the proton drip line. In this project, the gamma-detector array as well as the charged particle detector system, combined with Gas-filled Recoil Separator, will be employed in Recoil-Isomer Tagging (RIT) technique for probing high-spin states of exotic nuclei 150,151Tm. Using the RIT technique, whereby the delayed gamma-rays following the decay of isomeric states measured at the focal plane of the recoil separator is used to identify the prompt gamma-rays of nuclei produced in fusion-evaporation reaction at the target chamber, the high-spin states across the known isomeric states in nuclei 150,151Tm can be established. The aim of program is to investigate more comprehensive information on multi-particle excitations and to search magnetic rotation and superdeformation bands in nuclei 150,151Tm. The results will provide a step towards a systematic study of the single- and multi-particle excitations of nuclei close to the Z=64, N=80 shell closure and pave the way towards the possible observation of new phenomena in nuclear structure caused by the large excess off protons.

兰州充气反冲谱仪的建成运行为开展近质子滴线核结构研究提供了新的机遇。本项目将基于兰州充气反冲谱仪，结合高纯锗探测阵列(靶位置)及焦平面的探测系统，采用反冲余核同核异能态标记(Recoil-Isomer Tagging)方法，开展近质子滴线核150,151Tm的高自旋态研究。由重离子熔合蒸发反应产生目标核，经充气谱仪分离并传输至焦平面，通过焦平面位置探测同核异能态衰变的延时gamma与反应靶位置的瞬时gamma进行关联，建立目标核的高自旋能级纲图，分析其能级结构特点。着重研究150,151Tm的多准粒子激发结构，寻找磁转动及超形变转动带，探索其形成机制。结合理论计算及邻近核系统性，探讨Z=64,N=80双闭壳附近质子滴线核的奇异结构。

本项目的初始研究内容为基于兰州充气反冲谱仪，结合高纯锗探测阵列(靶位置)及焦平面的探测系统，采用反冲余核同核异能态标记(Recoil-Isomer Tagging)方法，开展近质子滴线核150,151Tm 的高自旋态研究。但在项目的执行过程中，因充气反冲谱仪靶室位置的改造尚未完成，不能进行相关实验，我们修改了实验内容，开展了弱束缚核9Be在位垒附近的熔合及破裂研究。我们测量了9Be+169Tm，181Ta，186W及187Re四个系统的熔合及单中子转移反应截面。取得的成果有：（1）通过比较实验熔合截面与未考虑破裂效应的耦合道理论计算结果，发现在熔合位垒附近此四系统的完全熔合截面均被抑制了30%。（2）抑制比与非完全熔合的截面占总熔合截面的比例数值相当。（3）弱束缚核9Be的熔合截面抑制比与靶的原子序数无关。这些研究成果已撰写多篇学术论文，其中有3篇发表在Physics Review C上。