Structure of nuclei far from stability

原子核结构远不稳定

• 批准号: 371656-2010
• 负责人: Starosta, Krzysztof
• 金额: $ 7.29万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=483673
• 关键词: Structure; nuclei; far; stability

The region of N=Z nuclei between 58Ni and 100Sn became the subject of vigorous theoretical and experimental studies due to a remarkable diversity of shapes. Ground-state shapes in these nuclei are predicted to evolve from spherical to triaxial, oblate, prolate, and back to spherical as the mass increases due to the occupation of identical deformation-driving orbitals. Moreover, the excited levels can have significantly different structure than the ground state. For example, in 68Se and 72Kr the oblate-deformed ground state band is reported to coexist with a prolate-deformed excited band. Variations in the excitation energy of low-lying states in this region are often used to analyze the evolution of structure away from the doubly-magic 56Ni core. However, electromagnetic transition rates are recognized as providing a more sensitive probe of collectivity and deformation. The goal of the current proposal is to initiate a program of studies addressing electromagnetic transition rates in heavy nuclei along the N=Z line aimed at the measurements of quadrupole deformation and triaxiality, as well as the identification of signatures of shape transitions and shape coexistence. The experimental methods of choice are the Recoil Distance Method (RDM) and the Doppler Shift Attenuation Method (DSAM) for lifetimes longer and shorter then 1 picosecond, respectively. States of interest will be populated following compound nucleus reactions; the experimental setup will include the TIGRESS array, the TIGRESS integrated plunger (TIP) device working in conjunction with an array of CsI charged-particle detectors, and, in the future, the DESCANT array of neutron detectors. The first experiments will address shape coexistence in 68Se and 72Kr populated via the 40Ca(36Ar,2alpha) and 40Ca(40Ca,2alpha) reactions, respectively.

在58 Ni和100 Sn之间的N=Z核区域由于形状的显著多样性而成为理论和实验研究的主题。 这些核的基态形状预计将从球形发展到三轴，扁圆，扁长，并返回到球形的质量增加，由于占用相同的变形驱动轨道。此外，激发能级可以具有与基态显著不同的结构。例如，在68 Se和72 Kr中，扁长形变的基态带被报道与扁长形变的激发带共存。 在这个区域的低激发态的激发能的变化经常被用来分析远离双魔56 Ni核的结构演化。然而，电磁跃迁率被认为是提供了一个更灵敏的探针的集体和变形。目前建议的目标是启动一个研究方案，解决重核沿着N=Z线的电磁跃迁率，旨在测量四极形变和三轴性，以及识别形状转变和形状共存的签名。实验方法的选择是反冲距离法（RDM）和多普勒频移衰减法（DSAM）的寿命长于和短于1皮秒，分别。感兴趣的状态将填充以下复合核反应;实验装置将包括TIGRESS阵列，TIGRESS集成柱塞（TIP）设备与CsI带电粒子探测器阵列一起工作，以及将来的中子探测器下降阵列。第一个实验将分别通过40 Ca（36 Ar，2alpha）和40 Ca（40 Ca，2alpha）反应解决68 Se和72 Kr中的形状共存问题。