Pollock Christopher J, Debefve Louise M
Cornell High Energy Synchrotron Source, Wilson Laboratory, Cornell University, Ithaca, New York 14853, United States.
Inorg Chem. 2023 Aug 28;62(34):13681-13691. doi: 10.1021/acs.inorgchem.3c01930. Epub 2023 Aug 14.
Valence-to-core X-ray emission spectroscopy (VtC XES) is an emerging technique that uses hard X-rays to probe the valence electronic structure of an absorbing atom. Despite finding varied applications for light elements and first row transition metals, little work has been done on heavier elements such as second and third row transition metals. This lack of application is at least partially due to the relatively low resolution of the data at the high energies required to measure these elements, which obscures the useful chemical information that can be extracted from the lower energy, higher resolution spectra of lighter elements. Herein, we collect data on a set of platinum-containing compounds and demonstrate that the VtC XES resolution can be dramatically enhanced by exciting the platinum atom in resonance with its L-edge white line absorption. Whereas spectra excited using standard nonresonant absorption well above the Pt L-edge display broad, unfeatured VtC regions, resonant XES (RXES) spectra have more than twofold improved resolution and are revealed to be rich in chemical information with the ability to distinguish between even closely related species. We further demonstrate that these RXES spectra may be used to selectively probe individual components of a mixture of Pt-containing compounds, establishing this technique as a viable probe for chemically complex samples. Lastly, it is shown that the spectra are interpretable using a molecular orbital framework and may be calculated using density functional theory, thus suggesting resonant excitation as a general strategy for extracting chemically useful information from heavy element VtC spectra.
价层到内层X射线发射光谱（VtC XES）是一种新兴技术，它利用硬X射线探测吸收原子的价电子结构。尽管该技术在轻元素和第一行过渡金属方面有多种应用，但对于诸如第二行和第三行过渡金属等较重元素的研究却很少。这种应用的缺乏至少部分是由于在测量这些元素所需的高能量下数据分辨率相对较低，这使得从较轻元素的低能量、高分辨率光谱中可以提取的有用化学信息变得模糊。在此，我们收集了一组含铂化合物的数据，并证明通过使铂原子与其L边白线吸收共振激发，可以显著提高VtC XES的分辨率。使用高于Pt L边的标准非共振吸收激发的光谱显示出宽的、无特征的VtC区域，而共振XES（RXES）光谱的分辨率提高了两倍多，并且显示出丰富的化学信息，甚至能够区分密切相关的物种。我们进一步证明，这些RXES光谱可用于选择性探测含铂化合物混合物的各个成分，从而将该技术确立为化学复杂样品的可行探测方法。最后，结果表明这些光谱可以用分子轨道框架进行解释，并且可以使用密度泛函理论进行计算，因此表明共振激发是从重元素VtC光谱中提取化学有用信息的一般策略。
