Electromagnetic nuclear moments around neutron magic number 20 and 28

本研究的目的是通过测量电磁核矩来研究中子幻数N = 20和28附近的远丰中子核的结构。在N = 20的核区域，在法国GANIL测量了33Al的基态电四极矩。在常规sd模型空间内，得到的Q值与单颗粒值和壳模型计算值有很大的向外差异，表明N = 20壳封闭的侵蚀。对于N = 28区域，在RIKEN RIBF设施测量了320 keV下43 S异构态的Q矩。数据表明，43 S的形变是温和的，尽管水平反转，这表明一个强大的变形的基态和形状共存的低洼状态。在这项研究中，一个高贵的方法来产生自旋取向RI光束利用两步碎裂反应结合动量色散匹配的离子光学技术已经开发出来。

The purpose of this study is to investigate the structure of far neutron-rich nuclei around neutron magic number N = 20 and 28 through the measurement of electromagnetic nuclear moments. In the nuclear region of N = 20, a ground-state electric quadrupole (Q) moment of 33Al was measured at GANIL, France. The obtained Q shows a large outward discrepancy from a single particle value and shell model calculations within the conventional sd model space, suggesting the erosion of N = 20 shell closure. For the N = 28 region, the Q moment of the isomeric state of 43S at 320 keV was measured at the RIKEN RIBF facility. The data shows that the 43S deformation is modest in spite of the level inversion, suggesting a strong deformation of the ground state and a shape coexistence in the low-lying states. In this study, a noble method to produce spin-aligned RI beams utilizing two-step fragmentation reaction combined with momentum dispersion-matching of the ion optics technique has been developed.