The Soft X-ray Spectrometer (SXS) on board \textit{Hitomi}, with the unprecedented resolving power of R$\sim$1250, allowed the detection of members of the Fe XXV \ka\ complex emission spectra from the center of the Perseus Cluster. In this paper, we introduce a novel method of measuring the column density using the optically thin (Case A) to optically thick (Case B) transition for one- and two-electron systems. We compare the Fe XXV K$\alpha$ line ratios computed with CLOUDY with that from the \textit{Hitomi} observations in the outer region of the Perseus core using collision strengths from different atomic datasets, and obtain good agreement. We also show the effect of turbulence on Fe XXV K$\alpha$ line ratios and interplay between column density and metallicity. Besides, we discuss the atomic number dependence of transition probabilities for allowed and non-allowed transitions, which causes the highly charged He-like systems, such as Fe XXV, to behave fundamentally differently from He I.

中文翻译：

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微量热仪时代的 X 射线光谱学。二、H-类和He-类铁从A到B转变的柱密度新诊断

\textit{Hitomi} 上的软 X 射线光谱仪 (SXS) 具有前所未有的 R$\sim$1250 分辨能力，允许检测来自英仙座中心的 Fe XXV \ka\ 复合发射光谱的成员簇。在本文中，我们介绍了一种使用单电子和双电子系统的光学薄（情况 A）到光学厚（情况 B）跃迁测量柱密度的新方法。我们使用来自不同原子数据集的碰撞强度将使用 CLOUDY 计算的 Fe XXV K$\alpha$ 线比与来自英仙座核心外部区域的 \textit{Hitomi} 观测值进行比较，并获得良好的一致性。我们还展示了湍流对 Fe XXV K$\alpha$ 线比的影响以及柱密度和金属丰度之间的相互作用。除了，