A majority of Er in the universe is synthesized by the r -process, which can occur in the mergers of neutron stars (NSs). The contribution of this element to the opacity of NS ejecta should be tested, but even the energy levels of first excited configuration have not been fully presented. The main aim of this paper is to present accurate energy levels of the ground [Xe]4 f 12 and first excited [Xe]4 f 11 5 d configurations of Er 2+ . The energy level structure of the Er 2+ ion was computed using the multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction (RCI) methods, as implemented in the GRASP2018 program package. The Breit interaction, self-energy, and vacuum polarization corrections were included in the RCI computations. The zero-first-order approach was used in the computations. Energy levels with the identification in LS coupling for all (399) states belonging to the [Xe]4 f<...

中文翻译：

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Er 2+的能级结构和跃迁数据

宇宙中的大多数Er是通过r过程合成的，该过程可能发生在中子星（NSs）的合并中。应该测试该元素对NS喷射的不透明性的贡献，但即使是首次激发构型的能级也没有被完全呈现出来。本文的主要目的是提供Er 2+的地面[Xe] 4 f 12和第一激发[Xe] 4 f 11 5 d构型的准确能级。Er 2+离子的能级结构是使用多重配置Dirac–Hartree–Fock和相对论配置相互作用（RCI）方法计算的，该方法在GRASP2018程序包中实现。RCI计算中包括了Breit相互作用，自能和真空极化校正。在计算中使用了零一阶方法。