The influence of the symmetry energy on the giant monopole resonance of neutron-rich nuclei analyzed in Thomas-Fermi theory
The influence of the symmetry energy on the giant monopole resonance of neutron-rich nuclei analyzed in Thomas-Fermi theory
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托马斯-费米理论分析对称能对富中子核巨单极子共振的影响
DOI：
10.1088/0954-3899/37/7/075107
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Centelles M
中科院分区：
文献类型：
--
作者：
Centelles M
利用相对论扩展的B-Fermi方法，在标度和约束计算中，分析了对称能密度依赖性对稳定丰中子核和奇异丰中子核中同位旋巨磁共振（GMR）平均激发能的影响.对于有效的核相互作用，我们采用相对论平均场模型补充的isoscalar-isovector介子耦合，允许一个修改的对称性能量的密度依赖性，而不损害成功的模型的结合能和电荷半径。巨磁电阻的平均能量的半经典估计是已知的，在充分RPA计算得到的结果是很好的协议。本分析是沿着Pb和Zr同位素链进行的。在标度计算中，当对称能较软时，激发能较大。同样的情况也发生在小中子过剩和中等中子过剩的原子核的约束计算中。然而，对于大的同位旋核的约束激发能变得更小的模型具有软对称性的能量。这种效应主要是由于这些同位素中存在松散束缚的外中子。估计的共振宽度的急剧增加被发现在很大程度上是富中子同位素，即使是重核，这是增强时的对称性能量的模型是软的。结果表明，在大中子数下，巨磁电阻强度分布低能区的结构随核对称能密度的变化而发生显著变化，这在响应函数的RPA计算中值得进一步表征.
We analyze the influence of the density dependence of the symmetry energy on the average excitation energy of the isoscalar giant monopole resonance (GMR) in stable and exotic neutron-rich nuclei by applying the relativistic extended Thomas–Fermi method in scaling and constrained calculations. For the effective nuclear interaction, we employ the relativistic mean field model supplemented by an isoscalar–isovector meson coupling that allows one to modify the density dependence of the symmetry energy without compromising the success of the model for binding energies and charge radii. The semiclassical estimates of the average energy of the GMR are known to be in good agreement with the results obtained in full RPA calculations. The present analysis is performed along the Pb and Zr isotopic chains. In the scaling calculations, the excitation energy is larger when the symmetry energy is softer. The same happens in the constrained calculations for nuclei with small and moderate neutron excess. However, for nuclei of large isospin the constrained excitation energy becomes smaller in models having a soft symmetry energy. This effect is mainly due to the presence of loosely bound outer neutrons in these isotopes. A sharp increase of the estimated width of the resonance is found in largely neutron-rich isotopes, even for heavy nuclei, which is enhanced when the symmetry energy of the model is soft. The results indicate that at large neutron numbers the structure of the low-energy region of the GMR strength distribution changes considerably with the density dependence of the nuclear symmetry energy, which may be worthy of further characterization in RPA calculations of the response function.