Nuclear structure at extreme

在这个研究项目中，原子核的结构已经在各种极端条件下进行了研究。我们首先研究了高同位旋原子核的结构。高的同位旋表示中子数大于质子数或质子数大于中子数的情况。同位旋的z分量由（Z-N）/2给出，其中Z和N分别表示质子和中子数。同位旋的大小T应该大于或等于Tz。在中子数和质子数相等的原子核中，Tz=0，基态和低激发态都是T0。低同位旋对应于β稳定线上和附近的核（稳定核），其中质子和中子数相等或接近。另一方面，具有大T的核远离β稳定线，被称为不稳定核。在过去的十年中，人们已经弄清楚，不稳定核的结构与稳定核的结构有很大的不同。在这个项目中，我们研究了32 Mg，这是一个不稳定核的例子，及其附近。N20是一个神奇的数字。因此，从稳定核的观点来看，32 Mg应该是一个中子闭合核，并且应该具有球形基态。这已被证明是不正确的，实验和理论。相反，对~（32）Mg附近核的研究却很少。然而，我们现在可以通过使用东京大学小组正在开发的蒙特卡罗壳模型来进行这种研究。通过这样的研究，已经澄清，从稳定核的变化不是突然发生在某个核上，而是逐渐发生的，有效相互作用的π分量在其中起着至关重要的作用。除了上述研究外，还研究了包括高自旋态在内的球形形变跃迁。

In this research project, the nuclear structure has been studied at variousextremes. We first investigated the structure of nuclei at high isospin. High isospin indicates situations that the neutron number is greater than theproton number or vice versa. The z-component of isospin is given by (Z-N)/2 where Z and N mean the proton and neutron numbers, respectively. The magnitude of isospin, T, should be larger than or equal to Tz. In nuclei with equal numbers of neutrons and protons, Tz=0, and the ground and low-lying states are of T0. Low-isospin corresponds to the nuclei on and near the beta stability line (stable nuclei) where the proton and neutron numbers are equal or close to each other. On the other side, nuclei with large T are far from the beta stability line, being called unstable nuclei. It has been clarified during the past ten years that unstable nuclei have structure very different from the structure of stable nuclei. In this project, we studied 32Mg, which is an example of unstable nuclei, and its vicinity. The N20 is a magic number as well known. Therefore, on the standpoint of stable nuclei, 32Mg should be a neutron-closed nucleus, and should have a spherical ground state. This has been shown to be incorrect, experimentally and theoretically. On the contrary, studies on nuclei around 32Mg have hardly been done. We can now, however, carry out such studies by using the Monte Carlo shell model being developed by the group of the University of Tokyo. By such studies, it has been clarified that the change from stable nuclei does not occur suddenly at a certain nucleus but does occur gradually, and that the monopole component of the effective interaction plays a crucial role in this. In addition to the above studies, the spherical-deformed transition has been studied including high spin states.