First direct mass measurements of stored neutron-rich 129,130,131Cd isotopes with FRS-ESR
First direct mass measurements of stored neutron-rich 129,130,131Cd isotopes with FRS-ESR
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DOI：
10.1016/j.physletb.2016.01.039
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发表时间：
2016-03
影响因子：
4.4
通讯作者：
R. Knöbel;M. Diwisch;F. Bosch;D. Boutin;L. Chen;C. Dimopoulou;A. Dolinskii;B. Franczak;B. Fra
中科院分区：
文献类型：
--
作者：
R. Knöbel;M. Diwisch;F. Bosch;D. Boutin;L. Chen;C. Dimopoulou;A. Dolinskii;B. Franczak;B. Fra
使用 410 MeV/u 238 U 射弹束，通过放置在 GSI 飞行分离器 FRS 入口处的铍靶中的磨损裂变产生镉同位素。裂变碎片被 FRS 分离并注入同步存储环 ESR 中进行质量测量。等时质谱 (IMS) 在两种不同的实验条件下进行，在 FRS 的高分辨率中心焦平面处有或没有 Bρ 标记。在使用 Bρ 标记的实验中，注入碎片的磁刚度以 2⋅10−4 的精度确定。一种新的数据分析方法使用两个实验的组合数据集的相关矩阵，首次提供了 25 种稀有同位素的实验质量值。该方法的高灵敏度和选择性使得能够以每周几个原子的速度检测到核素。在这封信中，我们提出了首次直接测量的 129,130,131 Cd 同位素质量值。镉以及碲和锡同位素的实验质量值在 N= 82 时表现出明显的壳效应。壳淬火不能从单个新质量值中推断出来，也不能通过与明确考虑淬火特征的理论模型更好地一致。这与 γ 射线光谱的结论一致，并证实了现代壳模型计算。
A 410 MeV/u 238 U projectile beam was used to create cadmium isotopes via abrasion-fission in a beryllium target placed at the entrance of the in-flight separator FRS at GSI. The fission fragments were separated by the FRS and injected into the isochronous storage ring ESR for mass measurements. Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without Bρ-tagging at the high-resolution central focal plane of the FRS. In the experiment with Bρ-tagging the magnetic rigidity of the injected fragments was determined with an accuracy of 2⋅ 10− 4. A new method of data analysis, which uses a correlation matrix for the combined data set from both experiments, has provided experimental mass values of 25 rare isotopes for the first time. The high sensitivity and selectivity of the method have given access to nuclides detected with a rate of a few atoms per week. In this letter we present for the 129,130,131 Cd isotopes mass values directly measured for the first time. The experimental mass values of cadmium as well as for tellurium and tin isotopes show a pronounced shell effect towards and at N= 82. Shell quenching cannot be deduced from a single new mass value, nor by a better agreement with a theoretical model which explicitly takes into account a quenching feature. This is in agreement with the conclusion from γ-ray spectroscopy and confirms modern shell-model calculations.