The isotope ${}^{163}\mathrm{Ho}$ is in many ways the best candidate to perform experiments to investigate the value of the electron neutrino mass. It undergoes an electron capture process to ${}^{163}\mathrm{Dy}$ with an energy available to the decay, $Q_{\mathrm{EC}}$, of about 2.8 keV. According to the present knowledge, this is the lowest $Q_{\mathrm{EC}}$ value for such transitions. Here we discuss a newly obtained spectrum of ${}^{163}\mathrm{Ho}$, taken by cryogenic metallic magnetic calorimeters with ${}^{163}\mathrm{Ho}$ implanted in the absorbers and operated in anticoincident mode for background reduction. For the first time, the atomic deexcitation of the ${}^{163}\mathrm{Dy}$ daughter atom following the capture of electrons from the $5s$ shell in ${}^{163}\mathrm{Ho}$, the OI line, was observed with a calorimetric measurement. The peak energy is determined to be 48 eV. In addition, a precise determination of the energy available for the decay $Q_{\mathrm{EC}}=(2.858\pm 0.010_{\mathrm{stat}}\pm 0.05_{\mathrm{syst}})\mathrm{keV}$ was obtained by analyzing the intensities of the lines in the spectrum. This value is in good agreement with the measurement of the mass difference between ${}^{163}\mathrm{Ho}$ and ${}^{163}\mathrm{Dy}$ obtained by Penning-trap mass spectrometry, demonstrating the reliability of the calorimetric technique.

中文翻译：

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Ho163电子俘获谱的表征：迈向电子中微子质量测定的一步

同位素 ${}^{163}何$在许多方面都是进行实验以研究电子中微子质量值的最佳人选。它经历了电子捕获过程${}^{163}镝$ 拥有可用于衰变的能量， ${问}_{\mathrm{欧共体}}$，约为2.8keV。根据目前的知识，这是最低的${问}_{\mathrm{欧共体}}$这种过渡的价值。在这里，我们讨论了新获得的${}^{163}何$，由低温金属磁热计和 ${}^{163}何$植入吸收器中，并以反巧合模式操作以减少背景。第一次，原子的原子激发${}^{163}镝$ 子原子从电子中捕获后 $5s$ 壳内 ${}^{163}何$通过量热法观察到了OI线。峰值能量确定为48 eV。此外，精确确定可用于衰变的能量${问}_{\mathrm{欧共体}}=（2.858\pm 0.010_{\mathrm{统计}}\pm 0.05_{\mathrm{系统}}）\mathrm{keV}$通过分析光谱中线的强度获得。该值与测量之间的质量差非常吻合${}^{163}何$ 和 ${}^{163}镝$ 由Penning-trap质谱仪获得，证明了量热技术的可靠性。