Laboratory-scale NEXAFS spectroscopy for the investigation of Fe oxides and organic matter in soil

近边X射线吸收精细结构（NEXAFS）光谱探测所研究元素的氧化态和化学环境。因此，它可以表征矿物，也可以表征短程有序固体，无定形化合物和金属络合物。到目前为止，NEXAFS光谱学仅限于同步辐射。由于NEXAFS仪器严重超额预订，只有在经过漫长的、竞争激烈的审查过程后才能获准使用。然而，哥廷根激光实验室已经开发出一种基于激光驱动等离子体源的台式光谱仪。在软X射线辐射（<1 keV）的光谱范围内，它不仅可以在真空中，而且可以在环境条件（水，惰性气体）下进行C1 s，N1s，O 1 s，Ca 2 p，Mn 2 p和Fe 2 p光谱分析。在一个联合项目中，我们提议开发、测试和应用用于地球科学样品分析的台式NEXAFS光谱仪。哥廷根激光天文馆的分项目旨在提高光源的亮度，开发灵活的样品环境，并提高仪器的光谱分辨率。耶拿大学的分项目将侧重于应用NEXAFS光谱技术和软X射线辐射。在这里，该方法的优点和缺点方面的样品制备，检测限和辐射损伤的不同化合物在不同的矩阵进行了探讨。随后，特别关注铁氧化物（Fe 2 p，O 1 s）的定量和日益复杂的环境样品中有机物质（C1 s，N1s）的表征。在项目结束时，弗里德里希-席勒-耶拿大学将提供一台改进的新台式光谱仪。有了这个仪器，我们关闭了分析差距的表征结晶性差的矿物，金属络合物和铁氧化物相关的有机物。当样品需要在制备或取样后快速分析时，光谱仪将特别有价值，例如氧化还原敏感样品或易于快速老化的样品（亚稳的不良结晶Fe和Mn相，碳酸盐前体相）。此外，与同步加速器测量相比，分析成本将大大降低，并且可以实现更高的样品吞吐量。

Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy probes the oxidation state and the chemical environment of the element under investigation. Thus, it may characterize minerals, but also short-range ordered solids, amorphous compounds, and metal complexes. NEXAFS spectroscopy has so far been limited to synchrotron radiation. As NEXAFS instruments are heavily overbooked, access is granted only after a lengthy, highly competitive review process. However, a table-top spectrometer based on a laser-driven plasma source has been developed at the Laser-Laboratorium Göttingen. In the spectral range of soft X-ray radiation (<1 keV) it allows for C1s, N1s, O1s, Ca2p, Mn2p, and Fe2p spectroscopy not only in vacuum, but also at ambient conditions (water, inert gases). Within a joint project we propose to develop, test and apply the table-top NEXAFS spectrometer for the analysis of geoscientific samples. The sub-project of Laser-Laboratorium Göttingen aims at increasing the brilliance of the source, developing a flexible sample environment and increasing the spectral resolution of the instrument. The sub-project of the University of Jena will focus on the application of NEXAFS spectroscopy with soft X-ray radiation. Here, the strengths and weaknesses of the method with regard to sample preparation, detection limits and radiation damage of different compounds in different matrices are to be explored. Subsequently, special attention is paid to the quantification of Fe oxides (Fe2p, O1s) and the characterization of organic material (C1s, N1s) in environmental samples of increasing complexity.At the end of the project, an improved new table-top spectrometer will be available at the Friedrich-Schiller-Universität Jena. With this instrument we close the analytical gap for the characterization of poorly crystalline minerals, metal-complexes and Fe oxide-associated organic matter. The spectrometer will be particularly valuable when samples need to be analyzed quickly after preparation or sampling, such as redox-sensitive samples or samples prone to fast aging (metastable poorly crystalline Fe and Mn phases, carbonate precursor phases). In addition, analysis costs will be greatly reduced, and a higher sample throughput can be achieved compared to synchrotron measurements.