稀富中子物质中α簇的形成,Science

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稀富中子物质中α簇的形成
Science ( IF 56.9 ) Pub Date : 2021-01-14 , DOI: 10.1126/science.abe4688
Junki Tanaka _{1,

2,

3} , Zaihong Yang _{3,

4} , Stefan Typel _{1,

2} , Satoshi Adachi ₄ , Shiwei Bai ₅ , Patrik van Beek ₁ , Didier Beaumel ₆ , Yuki Fujikawa ₇ , Jiaxing Han ₅ , Sebastian Heil ₁ , Siwei Huang ₅ , Azusa Inoue ₄ , Ying Jiang ₅ , Marco Knösel ₁ , Nobuyuki Kobayashi ₄ , Yuki Kubota ₃ , Wei Liu ₅ , Jianling Lou ₅ , Yukie Maeda ₈ , Yohei Matsuda ₉ , Kenjiro Miki ₁₀ , Shoken Nakamura ₄ , Kazuyuki Ogata _{4,

11} , Valerii Panin ₃ , Heiko Scheit ₁ , Fabia Schindler ₁ , Philipp Schrock ₁₂ , Dmytro Symochko ₁ , Atsushi Tamii ₄ , Tomohiro Uesaka ₃ , Vadim Wagner ₁ , Kazuki Yoshida ₁₃ , Juzo Zenihiro _{3,

7} , Thomas Aumann _{1,

2,

14}

Affiliation

Technische Universität Darmstadt, Fachbereich Physik, Institut für Kernphysik, Schlossgartenstraße 9, 64289 Darmstadt, Germany.
GSI Helmholtz Center for Heavy Ion Research GmbH, Planckstraße 1, 64291 Darmstadt, Germany.
RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako 351-0198, Japan.
Research Center for Nuclear Physics, Osaka University, 10-1 Mihogaoka, Ibaraki 567-0047, Japan.
State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China.
Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France.
Department of Physics, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto 606-8502, Japan.
Faculty of Engineering, University of Miyazaki, 1-1 Gakuen, Kibanadai-nishi, Miyazaki 889-2192, Japan.
Cyclotron and Radioisotope Center, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
Department of Physics, Tohoku University, Sendai 980-8578, Japan.
Department of Physics, Osaka City University, Osaka 558-8585, Japan.
Center for Nuclear Study, The University of Tokyo, 2-1 Hirosawa, Wako 351-0198, Japan.
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan.
Helmholtz Research Academy Hesse for FAIR, Schlossgartenstraße 9, 64289 Darmstadt, Germany.

稳定原子核中的 α 粒子 α 衰变是重元素（例如铀）中放射性的一种常见模式，它会导致包含两个质子和两个中子的粒子损失。尽管经过了一个多世纪的研究，这些 α 粒子何时何地在稳定和不稳定的原子核中形成仍然是一个悬而未决的问题。田中等人。用高能质子轰击了一系列稳定的锡同位素，并检测到喷射出的 α 粒子，其丰度与质量数成反比（参见 Hen 的观点）。这一观察将 α 粒子积累与核表面的中子表皮厚度联系起来，适用于从放射性衰变到中子星动力学的模型。科学，这个问题 p。260; 另见第 232 锡同位素的质子轰击揭示了在核表面形成的 α 粒子，随着质量的增加而减少。富中子重核的表面，具有由过量中子形成的中子表皮，为研究稀富中子物质提供了一个重要的地面模型系统。通过使用准游离 α 簇敲除反应，我们获得了在富中子锡同位素表面形成 α 簇的直接实验证据。观察到的反应截面随着质量数的增加而单调减少，与理论预测非常一致，这意味着 α 团簇形成与中子表皮之间存在紧密的相互作用。反过来，这一结果要求修正中子表皮厚度与对称能密度依赖性之间的相关性，这对于理解中子星至关重要。我们的结果还为α衰变中α粒子的起源提供了自然的解释。

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Formation of α clusters in dilute neutron-rich matter

α particles in stable nuclei α Decay is a common mode of radioactivity in heavy elements such as uranium that entails the loss of particles comprising two protons and two neutrons. Despite more than a century of study, when and where these α particles form in stable and unstable nuclei alike remains an open question. Tanaka et al. bombarded a series of stable tin isotopes with high-energy protons and detected ejected α particles at an abundance inversely correlated with mass number (see the Perspective by Hen). This observation, relating α particle accumulation to the neutron skin thickness at the nuclear surface, bears on models spanning radioactive decay to neutron star dynamics. Science, this issue p. 260; see also p. 232 Proton bombardment of tin isotopes reveals α particle formation at the nuclear surface that diminishes with rising mass. The surface of neutron-rich heavy nuclei, with a neutron skin created by excess neutrons, provides an important terrestrial model system to study dilute neutron-rich matter. By using quasi-free α cluster–knockout reactions, we obtained direct experimental evidence for the formation of α clusters at the surface of neutron-rich tin isotopes. The observed monotonous decrease of the reaction cross sections with increasing mass number, in excellent agreement with the theoretical prediction, implies a tight interplay between α-cluster formation and the neutron skin. This result, in turn, calls for a revision of the correlation between the neutron-skin thickness and the density dependence of the symmetry energy, which is essential for understanding neutron stars. Our result also provides a natural explanation for the origin of α particles in α decay.

更新日期：2021-01-14

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