高精度电子俘获测量$^{111}$ In的$Q$值用于电子中微子质量测定
High-precision electron-capture $Q$ value measurement of $^{111}$In for electron-neutrino mass determination
摘要：
用双潘宁阱质谱仪JYFLTRAP精确测定了$^{111}$ Cd（$1/2^+$）的基态$^{111}$ In（$9/2^+$）电子俘获到基态的$Q$值。获得的值为857.63（17）keV，比原子质量评估2020（AME 2020）中提取的值精确近20倍。使用高精度电子捕获$Q$值测量以及$^{111}$ Cd的866.60（6）keV、864.8（3）keV、855.6（10）keV和853.94（7）keV的核能级数据来确定这四种状态在能量上是否允许潜在的超低$Q$值$β^{}$衰变或电子捕获衰变。我们的结果证实了866.60（6）keV的激发态与自旋宇称（$J^π$）为3/2 $^{+}$和864.8（3）keV的$J^π$ = 3/2 $^{+}$被排除，因为它们的电子捕获$Q$值小于0 keV，在大约20 $σ$和50 $σ$，分别。在能量上允许电子捕获衰减到853.94（7）keV（$J^π$ = 7/2 $^+$）和855.6（10）keV（$J^π$ = 3/2 $^+$）的激发态，其中$Q$值分别为3.69（19）keV和2.0（10）keV。允许衰变跃迁$^{111}$ In（9/2 $^{+}$）$\rightarrow$ $^{111}$ Cd（7/2 $^{+}$），其$Q$值为3.69（19）keV，是未来EC实验测量中微子质量的一个潜在的新候选者。结果表明，铟的水平$2p_{1/2}$为这个衰变分支导致一个显着增加的EC事件的数量在能量区域的电子中微子质量敏感。
英文摘要：
A precise determination of the ground state $^{111}$In ($9/2^+$) electron capture to ground state of $^{111}$Cd ($1/2^+$) $Q$ value has been performed utilizing the double Penning trap mass spectrometer, JYFLTRAP. A value of 857.63(17) keV was obtained, which is nearly a factor of 20 more precise than the value extracted from the Atomic Mass Evaluation 2020 (AME2020). The high-precision electron-capture $Q$ value measurement along with the nuclear energy level data of 866.60(6) keV, 864.8(3) keV, 855.6(10) keV, and 853.94(7) keV for $^{111}$Cd was used to determine whether the four states are energetically allowed for a potential ultra-low $Q$-value $β^{}$ decay or electron-capture decay. Our results confirm that the excited states of 866.60(6) keV with spin-parity ($J^π$) of 3/2$^{+}$ and 864.8(3) keV with $J^π$ = 3/2$^{+}$ are ruled out due to their deduced electron-capture $Q$ value being smaller than 0 keV at the level of around 20$σ$ and 50$σ$, respectively. Electron-capture decays to the excited states at 853.94(7) keV ($J^π$ = 7/2$^+$) and 855.6(10) keV ($J^π$ = 3/2$^+$), are energetically allowed with $Q$ values of 3.69(19) keV and 2.0(10) keV, respectively. The allowed decay transition $^{111}$In (9/2$^{+}$) $\rightarrow$ $^{111}$Cd (7/2$^{+}$), with a $Q$ value of 3.69(19) keV, is a potential a new candidate for neutrino-mass measurements by future EC experiments featuring new powerful detection technologies. The results show that the indium level $2p_{1/2}$ for this decay branch leads to a significant increase in the number of EC events in the energy region sensitive to the electron neutrino mass.
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