We observed electronic $K$ x rays emitted from muonic iron atoms using superconducting transition-edge sensor microcalorimeters. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic $K\alpha$ and $K\beta$ x rays together with the hypersatellite $K^h\alpha$ x rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the $L$-shell electrons, accompanied by electron side feeding. Assisted by a simulation, these data clearly reveal the electronic $K$- and $L$-shell hole production and their temporal evolution on the 10–20 fs scale during the muon cascade process.

中文翻译：

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电子KX射线的高精度光谱揭示μ子原子的去激发动力学

我们观察到电子 $钾$使用超导过渡边缘传感器微量热计从 μ 子铁原子发射的 x 射线。FWHM 中 5.2 eV 的能量分辨率使我们能够观察到电子特性的不对称宽轮廓$钾\alpha$ 和 $钾\beta$ x射线与超卫星一起 ${钾}^H\alpha$6 keV 左右的 x 射线。这个特征反映了负介子和介子对核电荷的时间依赖性筛选。$升$-壳层电子，伴随电子侧馈电。在模拟的辅助下，这些数据清楚地揭示了电子$钾$- 和 $升$- 介子级联过程中壳孔的产生及其在 10-20 fs 尺度上的时间演变。