A predictive understanding of soft x-ray near-edge absorption spectra of small molecules is an enduring theoretical challenge and of current interest for x-ray probes of molecular dynamics. We report the experimental absorption spectrum for the electron spectroscopy for chemical analysis (ESCA) molecule (ethyl trifluoroacetate) near the carbon 1s absorption edge between 285–300 eV. The ESCA molecule with four chemically distinct carbon sites has previously served as a theoretical benchmark for photoelectron spectra and now for photoabsorption spectra. We report a simple edge-specific approach for systematically expanding standard basis sets to properly describe diffuse Rydberg orbitals and the importance of triple excitations in equation-of-motion coupled-cluster calculations of the energy interval between valence and Rydberg excitations.

对小分子软X射线近边缘吸收光谱的预测性理解是一项持久的理论挑战，也是分子动力学X射线探针的当前关注点。我们报告了在285–300 eV之间的碳1s吸收边缘附近的化学分析电子光谱（ESCA）分子（三氟乙酸乙酯）的实验吸收光谱。具有四个化学上不同的碳位点的ESCA分子以前曾作为光电子光谱的理论基准，现在已成为光吸收光谱的理论基准。我们报告了一种简单的特定于边缘的方法，用于系统地扩展标准基集，以正确描述弥散的里德堡轨道以及三价激发在化合价和里德堡激发之间的能量间隔的运动方程耦合簇计算中的重要性。