Study of Unstable Nuclei by Delayd Neutron Spectroscopy

本项目新设计和建造了飞行时间中子计数器，用于观测β衰变丰中子子核激发态发射的缓发中子。计数器的性能满足设计要求。1994年，我们在理化学研究所（RIKEN）用这个计数器完成了^<15，17>B的衰变光谱。利用极化的^<15，17>B和中子测量，我们首次成功地获得了^<15，17>C的激发态自旋和宇称。我们正在准备公布这些结果。1993<14>年还用另一个中子计数器测量了~（40）Be的衰变谱，研究了丰中子核的特征现象--超允许跃迁。虽然我们不能观察到这样的跃迁，但最近观察到了强跃迁，该跃迁馈送到^ B中的低能量激发能级<14>。这个跃迁对于理解^ B的结构是有趣<14>的。下一个实验将在1995年7月进行。这部分研究已经发表，我们关于丰质子核的研究结果已在几个国际研讨会上发表，我们正准备提交。一些期刊和会议报道了一种分段探测器阵列的发展，这种阵列被设计成与中子计数器耦合。

In the project, time of flight neutron counter was newly designed and constructed to observe delayd neutrons emitting from excited states in neutron rich daughter nuclei of beta-decay. Performance of the counter satisfied the designed value. With this counter, we have done the decay spectroscopy of ^<15,17>B at the Institute of Physical and Chemical Research (RIKEN) in 1994. We have succeeded to obtain the spins and parities of excited levels in ^<15,17>C,for the first time, by using polarized ^<15,17>B and neutron measurements. We are preparing for publish these results. Further experiment will be done.The decay spectroscopy of ^<14>Be was also done in 1993 with another neutron counter to study the super allowed transitions, which is considered to be characteristic phenomena of neutron rich nuclei. Although we could not observe such a transition, strong transition feeding to the low energy excited level in ^<14>B was newly observed. This transition is interesting to understand the structure of ^<14>B.Next experiment will be done in July of 1995. The part of this study was already published.Oue result on the study of proton rich nuclei was presented in several international symposia and we are now preparing to submit. And the development of a segmented detector array, which was designed to be coupled to the neutron counter, was reported in several journals and in meetings.