Phase transitions of solids and structural transformations of molecules are canonical examples of important photo-induced processes whose underlying mechanisms largely elude our comprehension due to our inability to correlate electronic excitation with atomic position in real time. Here, we present a decisive step towards such new methodology based on water-window covering (284–543 eV) attosecond soft x-ray pulses that can simultaneously access electronic and lattice parameters via dispersive x-ray absorption fine-structure (XAFS) spectroscopy. We validate this approach with an identification of the ${\sigma }^{*}$ and ${\pi }^{*}$ orbital contributions to the density of states in graphite simultaneously with its lattice’s four characteristic bonding distances. This work demonstrates the potential of dispersive XAFS, in combination with attosecond pulses, as a powerful investigative tool that is equally applicable to gas, liquid, and condensed phase.

中文翻译：

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具有阿秒脉冲的石墨中的色散软X射线吸收精细结构光谱

固体的相变和分子的结构转变是重要的光诱导过程的典范实例，由于我们无法实时将电子激发与原子位置相关联，其基本机理在很大程度上使我们难以理解。在这里，我们提出了一种基于水窗覆盖（284–543 eV）亚秒软X射线脉冲的新方法的决定性步骤，该脉冲可以通过色散X射线吸收精细结构（XAFS）光谱同时访问电子和晶格参数。我们通过识别以下内容来验证此方法：${\sigma }^{*}$ 和 ${\pi }^{*}$轨道对石墨中态密度的贡献及其晶格的四个特征键合距离。这项工作证明了分散XAFS与阿秒脉冲相结合的潜力，它是一种功能强大的研究工具，同样适用于气相，液相和冷凝相。