Structure study of neutron-rich nuclei by unique method to understand "island of inversion" nuclei

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14492
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Kyushu University
• Principal Investigator: Nishibata Hiroki 九州大学, 理学研究院, 助教 (00782004)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 不安定原子核

Outline of Final Research Achievements

For neutron-rich nuclei with the neutron number close to the magic number 20, the anomalous structures, such as unexpected ground-state deformation, were suggested by several experiments. Because of such exotic structure, many experimental and theoretical approaches have been made to reveal the mechanism. In the present work, the structure of neutron-rich Al-31 was investigated by our unique method of beta-decay spectroscopy of spin-polarized Mg-31. As a result, the detailed level of Al-31, including newly assigned spins for 7 excited levels, was obtained. By comparing the experimental results with the large-scale shell-model calculations, it was found that various structures, such as spherical and deformed states, coexist in Al-31.

Free Research Field

原子核物理学

Academic Significance and Societal Importance of the Research Achievements

中性子過剰な魔法数20付近の原子核はその特異な構造が実験的に示唆され、その構造を解き明かすべく1990年代からさまざまな実験が実施されてきた。一方で、さまざまな研究にもかかわらずデータが存在するのは基底状態付近に限られ、特にスピンなどの情報は得られていないのが当時の現状であった。本研究では、Al-31の励起状態のスピンを含めた詳細な励起構造を明らかとし、この原子核領域における精密核分光研究における第一歩となったと考えられる。また、得られた中性子過剰核における知見は、宇宙の元素合成の解明にもつながると期待される。