Spectroscopic Study of Neutron-Rich Nuclei with Spin-Polarized Radioactive Nuclear Beams

远离稳定原子核的奇异结构引起了人们的极大兴趣，因为它们为我们对原子核的理解提供了严格的检验。我们提出了一种新的方法来确定远离稳定的原子核激发态的自旋对。关键的一点是，我们观察到自旋极化放射性核与β延迟粒子的衰变各向异性。我们将把这种方法应用于11Li，以研究N=8中子幻数在非常富中子核中的消失。该研究计划已在加拿大TRIUMF的ISAC设施获得高度优先批准，该设施是最先进的放射性核束设施。在2001年和2002年，我们完成了以下准备工作：(1)实现了高偏振11Li束流；(2)构建了专用束流线；(3)构建了射线、延迟中子和伽马射线探测系统。到2003财年末，所有工作都已完成。由于加速器故障，原定于2003年6月的光束时间被推迟。实验计划在2004年7月进行。

The exotic structure of nuclei far from the stability are attracting much interest because they provide stringent tests for our understanding of nuclei. We propose a new method to determine the spin-parities of excited states of nuclei far from the stability. The essential point is that we observe the beta-decay anisotropy from a spin polarized radioactive nucleus in coincidence with beta-delayed particles. We will apply this method to 11Li in order to investigate the disappearance of the N=8 neutron magic number in very neutron rich nuclei.The research proposal has been approved with high priority at ISAC facility of TRIUMF in Canada, which is a state-of-the-art radioactive nuclear beam facility. In 2001 and 2002, we achieved the following preparatory works :(1)Achieving highly polarized 11Li beam,(2)Constructing a dedicated beam-line(3)Constructing detector systems for beta-rays, beta-delayed neutrons, and gamma-rays.All have been done by the end of FY2003. The scheduled beam time in June 2003 was postponed due to accelerator trouble. The experiment is scheduled in July 2004.