Study of nuclear deformation along the neutron drip line via proton inelastic scattering

通过质子非弹性散射研究沿中子滴线的核变形

• 批准号: 15540257
• 负责人: NAKAMURA Takashi
• 金额: $ 2.37万
• 依托单位: Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540257/
• 关键词: Radioactive Beam; Inelastic scattering; Drip-line nuclei; Nuclear Deformation; 中性子ハロー; 魔法数の破れ; 中性子ハロー核; 殻構造の変化

We have studied inelastic scatterings of drip-line nuclei, ^<11>Be, ^<14>Be, ^<15>B, ^<17>B, ^<18>C and ^<19>C on a proton target as well as on a carbon target. In this study we aimed at exciting primarily the first excited state, which has information of deformation of these nuclei. The deformation of such nuclei have attracted much attention since the extreme neutron to proton ratio may cause the change of nuclear shell structures represented by the magicity loss, or even the decoupling effect on the valence neutrons.In this study, not only the bound excited states which can be measured by in-beam gamma spectroscopy, but also the unbound states which can be reached by the invariant mass spectroscopy. For the latter, we have developed a new drift chamber which can measure angles of an ejectile with very high accuracy (less than 0.1 deg). We have also developed a new scheme of analyzing two-neutron events, which was essential to specify the excited state in two-neutron halo nucleus ^<1 … More 4>Be.A series of experiments were performed at RIKEN accelerator Research facility, where the intense radioactive beam is available. The drip-line nuclei were produced by the projectile, fragmentation and purified through the fragment separator RIPS. The excitation energy was obtained either by the method mentioned above.We have observed for the first time the 1^<st> excited state of ^<17>B in the bound excited state and that of ^<14>Be just above the particle decay threshold at Ex=1.56 MeV. The cross sections for producing the first excited states in ^<17>B and ^<15>B suggest that the effective charges for these nuclei are extremely small compared to the conventional value. This may be related to the decoupling effect which was found for the neighboring nucleus ^<16>C. As for ^<14>Be, the first excited states located at 1.56 MeV, lower than that of ^<12>Be at 2.1 MeV. This suggests that the ^<14>Be has even more melted shell structure than the case of 12Be, which was recently found as a magicity-lost nucleus. However, the deformation parameter extracted for ^<14>Be was smaller than that of 12Be. This may be understood as a restoration of shell stability. This interesting findings are to be further studied with theories including the shell melting or cluster nature of these nuclei. For other nuclei, we have also observed a new state as well.We are now planning to use the different probe of alpha target, an ideal isoscalar probe. This may clarify the shape difference between the neutron distribution and the proton distribution. For the very extreme neutron/proton ratios, we expect more decoupled situation where neutrons moves independently of protons. Studies of such very exotic excitation is important to understand the behavior of very neutron rich nuclei. Less

我们研究了滴水线核的非弹性散射， ^<11> Be， ^<14> Be， ^<15> b， ^<17> b， ^<18> c和 ^<19> c在质子靶标和碳靶上。在这项研究中，我们旨在令人兴奋的初级激发状态，该状态具有这些核变形的信息。这种核的变形引起了很多关注，因为极度中性的质子比可能会导致核外壳结构的变化，甚至是对价中子的分离效应所代表的核壳结构，甚至是对价中子的去耦效应的变化，不仅可以通过梁上伽玛频谱仪，还可以通过不可结合的状态来衡量的绑定激发状态。对于后者，我们已经开发了一个新的漂移室，该室可以以非常高的精度测量弹出的角度（小于0.1度）。我们还开发了一种分析两种中子事件的新方案，这对于指定两种中子halo unous ^<1中的激发态至关重要。更多4> BE。滴水线核是由弹丸，碎片化产生的，并通过碎片分离器撕裂纯化。兴奋能量是通过上述方法获得的。我们首次观察到 ^<17> b的1 ^<st>激发态在结合的激发态中， ^<14>的激发态位于ex = 1.56 meV处的粒子衰变阈值之上。在 ^<17> b和 ^<15> B中产生第一个令人兴奋的状态的横截面表明，与常规值相比，这些核的有效电荷非常小。这可能与相邻核 ^<16> c的脱钩效应有关。至于 ^<14>，第一个兴奋状态位于1.56 MeV，低于 ^<12>的态度为2.1 MeV。这表明 ^<14>比12BE的情况更融化壳结构，该情况最近被发现是一种魔术般的核us。但是，提取的 ^<14> be提取的变形参数小于12BE。这可以理解为壳稳定性的恢复。这个有趣的发现将进一步研究理论，包括这些核的壳熔化或聚类性质。对于其他核，我们也已经观察到了一个新的状态。我们现在正计划使用不同的同级探针Alpha靶标的不同的探针。这可以阐明中子分布和质子分布之间的形状差。对于非常极端的中子/质子比率，我们期望中子独立于质子移动。对这种非常异国情调的兴奋的研究对于了解非常中子的核的行为很重要。较少的

项目成果

Y.Yanagisawa,..., T.Nakamura et al.: "The first excited state of 30Ne studied by proton inelastic scattering in reverse kinematics"Physics Letters B. 566. 84-89 (2003)

Y.Yanagisawa,..., T.Nakamura 等人：“通过反向运动学中的质子非弹性散射研究 30Ne 的第一激发态”物理快报 B. 566. 84-89 (2003)

Coulomb and nuclear breakup of halo nuclei

• DOI: 10.1016/j.nuclphysa.2004.01.057
• 发表时间: 2004-04
• 期刊: Nuclear Physics
• 作者: Takashi Nakamura

Sensitivity of r-process Nucleosynthesis to Light Element Nuclear Reactions

r 过程核合成对轻元素核反应的敏感性

• 发表时间: 2005
• 期刊: Astrophys.J 634
• 作者: T.Sasaqui;T.Kajino;G.J.Mathews;K.Otsuki;T.Nakamura
• 通讯作者: T.Nakamura

In-beam γ-ray spectroscopy of the neutron-rich boron isotopes ^<15,17>B via inelastic scattering on ^<12>C

通过 ^<12>C 上的非弹性散射对富中子硼同位素 ^<15,17>B 进行束内 γ 射线光谱分析

• 发表时间: 2005
• 期刊: Physical Review C (In press)
• 作者: Y.Kondo;T.Nakamura et al.
• 通讯作者: T.Nakamura et al.

Coulomb and nuclear breakup of a halo nucleus 11Be

• DOI: 10.1103/physrevc.70.054606
• 发表时间: 2004-09
• 期刊: Physical Review C
• 影响因子: 3.1
• 作者: N. Fukuda;T. Nakamura;N. Aoi;N. Imai;M. Ishihara;T. Kobayashi;H. Iwasaki;T. Kubo;A. Mengoni;M. Notani;H. Otsu;H. Sakurai;S. Shimoura;T. Teranishi;Y. Watanabe;K. Yoneda