Ultrafast X-ray scattering experiments are routinely analyzed in terms of the isotropic scattering component. Here, we present an analytical method for calculating total isotropic scattering for ground and excited electronic states directly from ab initio two-electron densities. The method is generalized to calculate the isotropic elastic, inelastic, and coherent mixed scattering. The presented computational results focus on the potential for differentiating between electronic states and the decomposition of the total scattering in terms of elastic and inelastic scattering. For the specific example of the umbrella motion in the first excited state of ammonia, we show that the redistribution of electron density along this coordinate leaves a comparably constant fingerprint in the total scattering that is similar in magnitude to the effect of changes in molecular geometry.

中文翻译：

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分子全同向散射中的激发电子态

通常根据各向同性散射分量对超快X射线散射实验进行分析。在这里，我们提出了一种直接从头算两个电子密度直接计算基态和激发电子态的总各向同性散射的分析方法。该方法被普遍用来计算各向同性的弹性，非弹性和相干混合散射。提出的计算结果集中在区分电子状态和根据弹性和非弹性散射的总散射分解上的潜力。对于在氨的第一激发态下伞运动的具体例子，