Magnetic quadrupole transitions in the relativistic energy density functional theory
Magnetic quadrupole transitions in the relativistic energy density functional theory
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相对论能量密度泛函理论中的磁四极跃迁
DOI：
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发表时间：
2022
影响因子：
2.7
通讯作者：
N. Paar
中科院分区：
文献类型：
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作者：
G. Kružić;T. Oishi;N. Paar
磁四极（M2）激发代表了原子核的一个基本特征，与自旋和轨道跃迁算子引起的核磁性相关。由于它仅在非相对论理论方法中进行研究，并且可用的实验数据相当有限，因此使用相对论核能量密度泛函框架研究 M2 跃迁的性质很有趣。在这项工作中，核基态是用相对论 Hartree-Bogoliubov 模型计算的，而 M2 激发是用相对论准粒子随机相位近似和用等向量-伪向量项扩展的剩余相互作用来描述的。描述并分析了闭壳核 $$^{16}$$ 16 O、$$^{48}$$ 48 Ca、$$^{208}$$ 208 Pb、开壳 $$^{18} mathrm O$$ 18 O、$$^{42}$$ 42 Ca、$$^{56}$$ 56 Fe 和半幻数 M2 转变强度分布$$^{90}$$ 90 锆。 M2 跃迁特性的演变已在 $$^{36-64} mathrm Ca$$ 36 - 64 C 同位素链内进行了研究。主要的 M2 跃迁具有相当丰富的基础结构，详细分析表明，由于贡献的粒子空穴构型数量较多，集体性随着质量数的增加而增加。开壳核中的配对相关性具有很强的影响，导致 M2 强度降低和质心能量向更高值移动。 M2 转变强度的分析表明，可能缺少大量的实验强度，这主要是由于相当有限的能量范围的限制。计算出的 Ca 同位素 M2 强度以及未来的实验数据将允许限制核介质中 g 因子的猝灭。
Magnetic quadrupole (M2) excitation represents a fundamental feature in atomic nucleus associated to nuclear magnetism induced by spin and orbital transition operator. Since it has only been investigated within the non-relativistic theoretical approaches, and available experimental data are rather limited, it is interesting to study the properties of M2 transitions using the framework of relativistic nuclear energy density functional. In this work the nuclear ground state is calculated with relativistic Hartree-Bogoliubov model, while the M2 excitations are described using the relativistic quasiparticle random phase approximation with the residual interaction extended with the isovector-pseudovector term. The M2 transition strength distributions are described and analyzed for closed shell nuclei $$^{16}$$ 16 O, $$^{48}$$ 48 Ca, $$^{208}$$ 208 Pb, open-shell $$^{18} mathrm O$$ 18 O , $$^{42}$$ 42 Ca, $$^{56}$$ 56 Fe, and semi-magic $$^{90}$$ 90 Zr. The evolution of M2 transition properties has been investigated within the $$^{36-64} mathrm Ca$$ 36 - 64 C a isotope chain. The main M2 transitions have rather rich underlying structure and detailed analysis shows that collectivity increases with the mass number due to larger number of contributing particle-hole configurations. Pairing correlations in open shell nuclei have strong effect, causing the reduction of M2 strength and shifts of the centroid energies to higher values. The analysis of M2 transition strengths indicate that considerable amount of experimental strength may be missing, mainly due to limitations to rather restricted energy ranges. The calculated M2 strengths for Ca isotopes, together with the future experimental data will allow constraining the quenching of the g factors in nuclear medium.