AI 中文总结
研究利用扩展的协变密度泛函理论研究偶偶镭同位素核形状演化，通过八极形变能量增益评估稳定性，提出简化分析方法确定关键单粒子能级，揭示张量耦合和配对关联对八极形变的影响。
AI 中文摘要
三维晶格空间中的协变密度泛函理论被扩展到含局域交换项的PCF - PK1泛函，用于研究偶偶镭同位素的核形状演化。发现\(^{222 - 228}\)Ra基态有明显的轴向八极形变，无三轴形状迹象。用八极形变能量增益评估其稳定性，\(^{224}\)Ra和\(^{226}\)Ra值较大。提出基于八极形变参数\(\beta_3 = 0\)时单粒子谱的简化分析方法，确定了驱动八极形变的关键单粒子能级。还发现增加张量耦合强度促进八极形变，降低配对强度使其稳定。结果为镭同位素链中八极形变提供微观理解，突出张量耦合和配对关联在反射不对称核形状中的重要性。
英文摘要
The covariant density functional theory in a three-dimensional lattice space is extended to the PCF-PK1 functional with localized exchange terms and is employed to study the nuclear shape evolution of even-even Ra isotopes. Well-developed axial octupole deformations are found for the ground states of $^{222-228}$Ra with no evidence of triaxial shapes. The energy gain of octupole deformation is employed to assess the stability of octupole deformation, with relatively larger values observed for $^{224}$Ra and $^{226}$Ra. A simplified analysis method based on the single-particle spectrum at the octupole deformation parameter $β_3=0$ is proposed to identify the key single-particle levels driving octupole deformation. It is found that the $m_z=3/2$ orbitals from $ν1j_{15/2}$ and $ν2g_{9/2}$ and the $m_z=1/2$ orbitals from $π1i_{13/2}$ and $π2f_{7/2}$, play crucial roles in the formation of octupole deformation in Ra isotopes. Furthermore, increasing the tensor coupling strength promotes octupole deformation, whereas reducing the pairing strength stabilizes it. Our results provide a microscopic understanding of octupole deformation in the Ra isotopic chain and highlight the importance of both tensor coupling and pairing correlations in reflection-asymmetric nuclear shapes.
Comments8 pages, 8 figures
