Precision mass measurements of 104Y, 106Zr, 104,104m,109Nb, and 111,112Mo have been performed with the JYFLTRAP double Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line facility. The order of the long-lived states in 104Nb was unambiguously established. The trend in two-neutron separation energies around the N=66 neutron midshell appeared to be steeper with respect to the Atomic Mass Evaluation 2020 extrapolations for the 39Y and 40Zr isotopic chains and less steep for the 41Nb chain, indicating a possible gap opening around Z=40. The experimental results were compared to the BSkG2 model calculations performed with and without vibrational and rotational corrections. All of them predict two low-lying minima for 106Zr. While the unaltered BSkG2 model fails to predict the trend in two-neutron separation energies, selecting the more deformed minima in calculations and removing the vibrational correction, the calculations are more in line with experimental data. The same is also true for the 21+ excitation energies and differences in charge radii in the Zr isotopes. The results stress the importance of improved treatment of collective corrections in large-scale models and further development of beyond-mean-field techniques.

中文翻译：

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锆区域的精确质量测量确定了 N = 66 处中子中壳的质量表面


104Y、106Zr、104,104m、109Nb 和 111,112Mo 的精确质量测量已在离子引导同位素分离器在线设施中使用 JYFLTRAP 双潘宁阱质谱仪进行。 104Nb 中的长寿态顺序已明确确定。相对于 39Y 和 40Zr 同位素链的 2020 年原子质量评估推断，N=66 中子中壳周围的双中子分离能的趋势似乎更陡峭，而 41Nb 链的陡峭程度较低，表明 Z 周围可能存在能隙=40。将实验结果与经过和不经过振动和旋转校正的 BSkG2 模型计算进行比较。他们都预测 106Zr 有两个低位最小值。虽然未改变的BSkG2模型无法预测双中子分离能的趋势，但在计算中选择变形较大的最小值并去除振动校正，计算结果更符合实验数据。对于 Zr 同位素中的 21+ 激发能和电荷半径差异也是如此。结果强调了改进大规模模型中集体校正处理和进一步发展超平均场技术的重要性。