arXiv 2602.190522026-02-24nucl-th

探测极小单极共振结构与其γ衰变

Probing the structure of pygmy dipole resonance with its gamma decay

Lanzhou University（兰州大学）；Shanghai Jiao Tong University（上海交通大学）；Università degli Studi di Milano（米兰大学）；INFN, Sezione di Milano（意大利国家核物理研究所米兰分部）

W. -L. Lv, Y. -F. Niu, G. Colò

备注：: 7 pages, 4 figures

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AI总结：

通过Skyrme粒子-振动耦合模型研究PDR的γ衰变特性，揭示其主要具有等标性质，并发现PDR波函数中复杂配置的成分小于IVGDR和ISGQR。

摘要：

核结构研究中，极小单极共振（PDR）的异ospin性质和集体性一直是长期存在的开放性问题。为回答这些问题，利用Skyrme粒子-振动耦合（PVC）模型研究了PDR态在$^{208}$Pb中通过γ衰变到低能$2_{1}^{+}$态的过程。研究发现，PDR态到低能$2_{1}^{+}$态的E1γ衰变比异矢量巨单极共振（IVGDR）到该态的衰变被强烈抑制，这揭示了PDR主要具有等标性质。对衰变幅图中贡献于衰变过程的各过程幅度的分解显示，在PDR波函数中存在非可忽略的1粒子-1空穴配置耦合到$2_1^{+}$声子的成分。此外，我们提供了一种量化方法来识别波函数中复杂配置的成分，发现PDR中的此类成分比IVGDR中的小，比等标巨四极共振（ISGQR）中的要小得多。

英文摘要：

The isospin properties and the collectivity of the pygmy dipole resonance (PDR) are long-standing open questions in nuclear structure studies. To answer these questions, the $γ$-decay of PDR states in $^{208}$Pb to the low-lying $2_{1}^{+}$ state is investigated using the Skyrme particle-vibration coupling (PVC) model. It is found that the $E1$ $γ$ decay from the PDR states to the low-lying $2_{1}^+$ state is strongly suppressed compared to that from the isovector giant dipole resonance (IVGDR), which reveals the predominantly isoscalar character of PDR. A detailed decomposition of the decay diagrams of the amplitudes of the processes contributing to the decay demonstrates the non-negligible presence of the 1 particle-1 hole configurations coupled to the $2_1^{+}$ phonon in the PDR wave function. Furthermore, we give a quantitative way to identify the components of complex-configurations in the wave function, and it is found that such component in PDR is smaller than that in IVGDR and much smaller than that in isoscalar giant quadrupole resonance (ISGQR).

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