直接测量$^{72}$ As- $^{72}$ Ge的质量差排除了$^{72}$ As作为确定中微子质量的有希望的$β$衰变候选者的可能性
Direct measurement of the mass difference of $^{72}$As-$^{72}$Ge rules out $^{72}$As as a promising $β$-decay candidate to determine the neutrino mass
摘要：
我们报告的第一个直接测定的基态到基态的电子捕获$Q$ -值的$^{72}$作为$^{72}$锗衰变通过测量它们的原子质量差，利用双潘宁阱质谱仪，JYFLTRAP。测得的$Q$值为4343.596（75）keV，与最新的原子质量评估2020中的值相比，精度提高了50倍以上。此外，发现新的$Q$值低12.4（40）keV（3.1 $σ$）。随着基态到基态的$Q$ -值的不确定性的显著降低，结合$γ$ -射线光谱的$^{72}$ Ge的能级图，我们确认了五个潜在的超低$Q$ -值${β^{+}}$ -衰变或电子捕获跃迁在能量上是被禁止的，从而排除了所有作为电子中微子质量测定的可能候选者的跃迁。然而，小的负$Q$ -值的发现开辟了使用$^{72}$ As研究虚拟$β$ - $γ$转换的可能性。
英文摘要：
We report the first direct determination of the ground-state to ground-state electron-capture $Q$-value for the $^{72}$As to $^{72}$Ge decay by measuring their atomic mass difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The $Q$-value was measured to be 4343.596(75)~keV, which is more than a 50-fold improvement in precision compared to the value in the most recent Atomic Mass Evaluation 2020. Furthermore, the new $Q$-value was found to be 12.4(40)~keV (3.1 $σ$) lower. With the significant reduction of the uncertainty of the ground-state to ground-state $Q$-value value combined with the level scheme of $^{72}$Ge from $γ$-ray spectroscopy, we confirm that the five potential ultra-low $Q$-value ${β^{+}}$-decay or electron capture transitions are energetically forbidden, thus precluding all the transitions as possible candidates for the electron neutrino mass determination. However, the discovery of small negative $Q$-values opens up the possibility to use $^{72}$As for the study of virtual $β$-$γ$ transitions.
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