Gamma-ray spectroscopy on neutron-rich nuclei via RI beam fragmentation method

本研究项目所取得的研究成果可以总结为以下两点。RI束的发展和新的富中子同位素的发现。为了将RI束破碎方法应用于N=28的较重的富中子核，我们使用了适合于有效生产原子核的强48Ca束来开发RI束。根据RIKEN实现的一种新的加速方案，光束强度增加了大约两个数量级。为了使用强光束，我们寻找新的富含中子的同位素。结果，我们首次发现了^<84>Ne, ^<87>Na和^<48>Si。此外，我们发现^<88>Ne, ^<86>Na和^<89>Mg是粒子非束缚核。^<48>Si的粒子稳定性表明在Z ~ 14和N ~ 28区域可能存在魔力损失。所有的研究结果都在一篇期刊论文和一次新闻发布会上发表了。为了克服RI波束碎片化方法的缺点，我们开发了两种测量激发态平均寿命的新方法：多普勒频移衰减法（DSAM）和反冲阴影法（CRSM）。这两种方法分别应用于^<12>Be和^<16>C两个轻核。我们发现180的第一激发态的平均寿命是惊人的长。这项新的挑战正在得到科学研究资助(A)(2) 16204017的支持。

The research results obtained in this research project are summarized in the following two points.1.Development of RI beams and discovery of new neutron-rich isotopes.To apply the RI beam fragmentation method for heavier neutron rich nudei with N=28, we developed RI beams by using an intense 48Ca beams, which is appropriate for efficient productions of the nuclei. According to a new acceleration scheme realized at RIKEN, the beam intensity was increased by about two orders of magnitudes. To use the intense beam, we searched for new neutron-rich isotopes. As a result, we found for the first time ^<84>Ne, ^<87>Na and ^<48>Si. In addition, we found that ^<88>Ne, ^<86>Na and ^<89>Mg are particle-unbound nuclei. The fact of the particle stability for ^<48>Si suggests a possible magicity-loss in the Z〜14 and N〜28 region. All of the findings were shown in a Journal paper as well as in a press conference.2.Development of new techniques for measuring mean-lives of excited statesTo overcome disadvantages in the RI beam fragmentation method, we developed two new methods to measure mean-lives of excited states, Doppler Shift Attenuation Method (DSAM) and the Recoil Shadow Method CRSM). These two methods were applied for two light nuclei, ^<12>Be and ^<16>C. We found that the mean-life of the first excited state of 180 is surprisingly long. This new challenging are being supported by the Grant-in-Aid for Scientific Research (A)(2) 16204017.