2019 Fiscal Year Final Research Report
Exotic structure of very neutron-rich nuclei --- Search for shape coexistence and clarifying its mechanism
| Project/Area Number |
17H02891
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Osaka University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
小田原 厚子 大阪大学, 理学研究科, 准教授 (30264013)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | 中性子超過剰核 / 中性子魔法数20 / 変形共存 / 平均場と核子間相関の競争 / ベータ・ガンマ・中性子核分光法 / 31Al,33Al核の構造 / 不安定核ビーム31Mg,33Mg / カナダTRIUMF研究所 |
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| Outline of Final Research Achievements |
The exotic structures of very neutron-rich nuclei have been attracting much attention. One of the highlights is the discovery of “shape coexistence” in 31Mg by our group in 2017. It was found that the coexistence of various structures is realized as a result of competition between the spherical mean field which favors spherical shapes and the nuclear correlation which favors deformed shapes.
To investigate the shape coexistence in more neutron-rich nuclei, it is essential to detect the beta-delayed neutrons because of less neuron threshold. We have developed a new neutron detector system to investigate the shape coexistence phenomena in wide region of nuclear chart. In fall of 2019 we have successfully performed the beta-decay spectroscopy experiment with the radioactive nuclear beam of 33Mg at TRIUMF. The preliminary results show, for the first time, the excited states in 33Al above the neutron threshold. The detailed analyses are in progress to reveal the exotic structure of 33Al.
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| Free Research Field |
実験原子核物理学
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| Academic Significance and Societal Importance of the Research Achievements |
中性子の数が極端に多い不安定核（超非対称核子系）は、宇宙における元素合成の過程で重要な役割を果たしているはずだが、それらの核構造はほとんど未知であり、元素合成への寄与を定量的に評価し難い状況にあった。
我々のグループは、これらの不安定核を二次ビームとして生成し、そのスピンの向きを偏らせ、ベータ崩壊を詳細に調べるという独自の手法を用いることによって、超非対称核子系では様々な形に変形した状態が励起エネルギーの狭い領域に出現していること（変形共存）を初めて明らかにした。本研究では、それに続く系統的研究を行うための中性子検出器系の開発に成功した。喫緊の課題となっている不安定核の構造が解明される日は近い。
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