To explore the properties of neutron-rich nuclei with approximately 40 protons, the density-dependent point coupling (DD-PC1) effective interaction parameter is adopted in the relativistic mean-field theory with the complex momentum representation (RMF-CMR). The calculated two-neutron separation energy (S _2n ) and root-mean-square (rms) radii support the halo structure that appear in Mo and Ru isotopic chains. Besides, the neutron skin structures appear in Kr and Sr isotopes. The conclusions drawn are also supported by the single-particle energy levels and their occupancy probability and density distribution. Particularly, the energy levels, which reduce to bound states or are approximately 0 MeV with a small orbital angular momentum, are suggested to provide the primary contribution to increasing the neutron radius. Moreover, the single-particle energy levels significantly reflect the shell structure. In addition, the neutron drip line nuclei for Kr, Sr, Mo, and Ru elements are proposed via the changes in S _2n .

为了探索具有大约 40 个质子的富中子核的性质，在具有复动量表示的相对论平均场理论 (RMF-CMR) 中采用了密度相关点耦合 (DD-PC1) 有效相互作用参数。计算出的二中子分离能 ( S _{2 n} ) 和均方根 (rms) 半径支持出现在 Mo 和 Ru 同位素链中的晕结构。此外，Kr和Sr同位素中出现中子表皮结构。得出的结论也得到了单粒子能级及其占据概率和密度分布的支持。特别是，降低到束缚态或大约为 0 MeV 且具有小轨道角动量的能级被建议为增加中子半径提供主要贡献。此外，单粒子能级显着反映了壳结构。此外，Kr、Sr、Mo 和Ru 元素的中子滴线核是通过S _{2 n} 的变化提出的。