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arXiv 2011.13288nucl-exnucl-th
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As、Se和Br核的质量测量及其对N=Z线质子-中子相互作用强度的意义

Mass measurements of As, Se and Br nuclei and their implication on the proton-neutron interaction strength towards the N=Z line

I. Mardor, S. Ayet San Andres, T. Dickel, D. Amanbayev, S. Beck, J. Bergmann, H. Geissel, L. Grof, E. Haettner, C. Hornung, N. Kalantar-Nayestanaki, G. Kripko-K… 展开作者

I. Mardor, S. Ayet San Andres, T. Dickel, D. Amanbayev, S. Beck, J. Bergmann, H. Geissel, L. Grof, E. Haettner, C. Hornung, N. Kalantar-Nayestanaki, G. Kripko-Koncz, I. Miskun, A. Mollaebrahimi, W. R. Plass, C. Scheidenberger, H. Weick, S. Bagchi, D. L. Balabanski, A. A. Bezbakh, Z. Brencic, O. Charviakova, V. Chudoba, P. Constantin, M. Dehghan, A. S. Fomichev, L. V. Grigorenko, O. Hall, M. N. Harakeh, J. P. Hucka, A. Kankainen, O. Kiselev, R. Knobel, D. A. Kostyleva, S. A. Krupko, N. Kurkova, N. Kuzminchuk, I. Mukha, I. A. Muzalevskii, D. Nichita, C. Nociforo, Z. Patyk, M. Pfutzner, S. Pietri, S. Purushothaman, M. P. Reiter, H. Roesch, F. Schirru, P. G. Sharov, A. Spataru, G. Stanic, A. State, Y. K. Tanaka, M. Vencelj, M. I. Yavor, J. Zhao

备注：
11 pages, 4 figures, accepted for publication at Physical Review C
发表信息：
Phys. Rev. C 103, 034319 (2021)
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摘要：

使用FRS离子捕获器的多次反射飞行时间质谱仪（MR-TOF-MS）对GSI FRS的$^{124}$初级束进行碎裂产生的$^{69}$ As、$^{70,71}$ Se和$^{71}$ Br同位素进行了质量测量，其质量分辨能力前所未有地接近1，000，000。对于$^{69}$ As同位素，这是第一次直接测量质量。仅用10个事件就实现了22 keV的质量不确定性。对于$^{70}$ Se同位素，获得了2.6 keV的质量不确定度，对应于$δ$ m/m = 4.0 $\times 10^{-8}$的相对精度，具有少于500个事件。测量了$^{71}$ Se和$^{71}$ Br同位素的质量，不确定度分别为23和16 keV。我们对$^{70,71}$ Se和$^{71}$ Br同位素的结果与2016年原子质量评估一致，我们对$^{69}$ As同位素的结果解决了以前间接测量之间的差异。我们还测量了$^{14}$ N $^{15}$ N $^{40}$ Ar（A=69）的质量，相对精度为$δ$ m/m = 1.7 $\times 10^{-8}$，我们的研究结果表明，测量到的质子-中子相互作用的再加强对于Z=29以上的N=Z线上的奇-奇核，（$δ$ V $_{pn}$）在N-Z=2时几乎不明显，在N-Z=4时也不明显。尽管如此，我们的质量测量证实了$δ$ V $_{pn}$沿N-Z=2和N-Z=4线的详细结构，可能会提供有关$\approx$ 500 keV的$^{70}$ Br同位素质量值差异的提示，这阻止了将其包括在超允许0 $^+\rightarrow$ 0 $^+$ $β$衰变的${Ft}$ -值的世界平均值中。所报告的工作为FRS离子捕获器在核图表的相同区域中的N=Z线处和N=Z线以外的核的质量测量奠定了基础，包括$^{70}$ Br同位素。

英文摘要：

Mass measurements of the $^{69}$As, $^{70,71}$Se and $^{71}$Br isotopes, produced via fragmentation of a $^{124}$Xe primary beam at the FRS at GSI, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher with an unprecedented mass resolving power of almost 1,000,000. For the $^{69}$As isotope, this is the first direct mass measurement. A mass uncertainty of 22 keV was achieved with only 10 events. For the $^{70}$Se isotope, a mass uncertainty of 2.6 keV was obtained, corresponding to a relative accuracy of $δ$m/m = 4.0$\times 10^{-8}$, with less than 500 events. The masses of the $^{71}$Se and $^{71}$Br isotopes were measured with an uncertainty of 23 and 16 keV, respectively. Our results for the $^{70,71}$Se and $^{71}$Br isotopes agree with the 2016 Atomic Mass Evaluation, and our result for the $^{69}$As isotope resolves the discrepancy between previous indirect measurements. We measured also the mass of $^{14}$N$^{15}$N$^{40}$Ar (A=69) with a relative accuracy of $δ$m/m = 1.7$\times 10^{-8}$, the highest yet achieved with a MR-TOF-MS. Our results show that the measured restrengthening of the proton-neutron interaction ($δ$V$_{pn}$) for odd-odd nuclei at the N=Z line above Z=29 (recently extended to Z=37) is hardly evident at N-Z=2, and not evident at N-Z=4. Nevertheless, detailed structure of $δ$V$_{pn}$ along the N-Z=2 and N-Z=4 lines, confirmed by our mass measurements, may provide a hint regarding the ongoing $\approx$500 keV discrepancy in the mass value of the $^{70}$Br isotope, which prevents including it in the world average of ${Ft}$-value for superallowed 0$^+\rightarrow$ 0$^+$ $β$ decays. The reported work sets the stage for mass measurements with the FRS Ion Catcher of nuclei at and beyond the N=Z line in the same region of the nuclear chart, including the $^{70}$Br isotope.

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