We report a high-statistics measurement of the $L/K$ orbital electron capture ratio in ${}^7\mathrm{Be}$ embedded in cryogenic Ta. The thin Ta film formed part of a high-resolution superconducting tunnel junction radiation detector that was used to identify the signals from different decay channels. The measured $L/K$ capture ratio of 0.070(7) is significantly larger than the only previous measurement of this quantity and the theoretical predictions that include in-medium effects. This value is a uniquely sensitive probe of the 1s and 2s orbital overlaps with the nucleus and is of relevance to nuclear and atomic physics, as well as Li production in novae and other astrophysical scenarios. This is the first experiment that uses superconducting tunnel junctions for nuclear-recoil detection, opening a new experimental avenue for low-energy precision measurements with rare isotopes.

中文翻译：

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在基于Ta的超导隧道结中直接测量^ {7} Be L / K捕获比。

我们报告了对 $\mathrm{大号}/ķ$ 轨道电子俘获比 ${}^7是$嵌入低温Ta中。Ta薄膜形成了高分辨率超导隧道结辐射探测器的一部分，该探测器用于识别来自不同衰减通道的信号。实测$\mathrm{大号}/ķ$捕获比率为0.070（7），远大于以前对该数量的唯一测量以及包括中等影响的理论预测。该值是与原子核1s和2s轨道重叠的唯一灵敏探针，与核和原子物理学以及新星和其他天体物理学场景中的Li产生有关。这是第一个使用超导隧道结进行核反冲探测的实验，为利用稀有同位素进行低能精度测量开辟了新的实验途径。