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近年来，29Ne作为N=20“反转岛”核区的关键核素，其基态价中子组态表现出与传统壳模型预期（f7/2轨道主导）相悖的p3/2轨道主导特征，并可能具有晕核结构。本研究基于相对论框架下的复动量表象（CMR）方法，系统分析了29Ne在四极形变（β2）影响下的单粒子能级演化、轨道占据概率及径向密度分布。计算结果表明：在球形极限（β2=0）下，2p1/2和2p3/2能级显著下移至1f7/2能级下方，形成典型的壳层反转；当β2 ≥ 0.58时，价中子占据由1f7/2分裂而成的3/2[321]轨道，但其主要组分为p3/2（占比68%），且径向密度分布显著弥散，符合晕核特征。这些结果揭示了29Ne的p波主导机制与形变协同作用对晕结构形成的影响，为反转岛核区的壳层演化提供了新的理论依据。
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关键词:
- 反转岛 /
- 晕核 /
- 复动量表象(CMR)方法 /
- 单粒子能级
Purpose: The neutron-rich nucleus 29Ne, located in the N = 20 “island of inversion,” challenges traditional shell-model predictions by exhibiting a ground-state valence neutron configuration dominated by the 2p3/2 orbital instead of the expected 1f7/2 orbital. This study aims to unravel the mechanisms behind this shell inversion and explore the potential halo structure in 29Ne, leveraging the interplay between weak binding, deformation, and low-l orbital occupancy.
Methods: We employ the complex-momentum representation (CMR) method within a relativistic framework, combining relativistic mean-field (RMF) theory with Woods-Saxon potentials to describe bound states, resonances, and continuum states. The model incorporates quadrupole deformation (β2) to analyze single-particle energy evolution, orbital mixing, and radial density distributions. Key parameters are calibrated to experimental data, including binding energies and neutron separation energies.
Key Results:
1. Shell Inversion: In the spherical limit (β2 = 0), the 2p1/2 and 2p3/2 orbitals drop below the 1f7/2 orbital, confirming the collapse of the N = 20 shell gap (see Figure below).
2. Deformation-Driven Halo: For β2 ≥ 0.58, the valence neutron occupies the 3/2[321] orbital (derived from 1f7/2), but with 68% p3/2 components due to strong l-mixing. This orbital exhibits a diffuse radial density distribution, signaling a halo structure.
3. Experimental Consistency: The predicted ground-state spin-parity (3/2-) and low separation energy (∼1 MeV) align with measurements, supporting 29Ne as a deformation-induced halo candidate.
Conclusions: The study demonstrates that 29Ne’s anomalous structure arises from the synergy of p-wave dominance and quadrupole deformation, which reduces centrifugal barriers and enhances spatial dispersion. The CMR method provides a unified description of bound and resonant states, offering new insights into the island of inversion and halo formation. Future work will incorporate pairing correlations and experimental validation of density distributions.
Significance: This work advances the understanding of exotic nuclear structures near drip lines and highlights the role of deformation in halo phenomena, with implications for future experiments probing neutron-rich nuclei.-
Keywords:
- Island Of Inversion /
- Halo Nucleus /
- Complex Momentum Representation Method /
- Single Particle Energy Level
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