Novel light sources have been new probes or “eyes” to develop our science and technology. Soft X-ray free-electron laser (SXFEL) is an ultrahigh brilliant soft X-ray source with ultrashort pulse-width, ultrahigh spatial coherence, and tunability of photon energy. Various experimental techniques are designed and examined with SXFEL. In this review, we focus on soft X-ray spectroscopies, such as magnetic spectroscopy, photoelectron spectroscopy, and non-linear spectroscopy, that were successfully developed at the SXFEL beamlines that generates vacuum ultraviolet ~ soft X-ray photons. These techniques allow us to track femtosecond dynamics of spins and carriers in materials element-selectively or to examine electronic states with the broken inversion symmetry. The SXFEL spectroscopies have become new tools to tackle with a wide range of our scientific and technical problems.

中文翻译：

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使用软X射线自由电子激光进行光谱学研究的最新进展

新颖的光源已成为发展我们科学技术的新探针或“眼睛”。软X射线自由电子激光器（SXFEL）是一种超高亮度软X射线源，具有超短脉冲宽度，超高空间相干性和光子能量可调性。使用SXFEL设计和检查了各种实验技术。在本文中，我们将重点放在软X射线光谱学上，例如磁能谱，光电子能谱和非线性能谱，它们是在产生真空紫外〜软X射线光子的SXFEL光束线上成功开发的。这些技术使我们能够选择性地跟踪材料中自旋和载流子的飞秒动态，或检查具有反转反转对称性的电子状态。