Miedema Piter S, Beye Martin
DESY Photon Science, FS-FLASH , Notkestraße 85 , 22607 Hamburg , Germany.
J Phys Chem Lett. 2018 May 17;9(10):2579-2583. doi: 10.1021/acs.jpclett.8b00720. Epub 2018 May 3.
The detection of the true soft X-ray absorption typically needs specially prepared submicrometer thin samples for transmission measurements. Bulk experiments instead have to rely on yield methods, for example, electron yield with limitations for insulating samples, sensitivity to applied fields, and with limited bulk sensitivity. Fluorescence yield methods instead do not have those limitations but have been found to deviate, in general, from the absorption spectrum. We demonstrate that restricting the detection to the 3s fluorescence channel (with the detector at a special angle where all polarizations contribute equally) restores the true X-ray absorption spectrum for all 3d-metal L edges. These theoretically derived results are rationalized by the lack of 3s-3d interaction in the core-excited state. Comparing X-ray absorption versus 3s-PFY for arbitrary detection geometries for both linear and circular polarized light, deviations appear that can become as large as 15%.
真正的软X射线吸收检测通常需要特别制备的亚微米薄样品用于透射测量。而块状样品实验则必须依赖产额方法，例如电子产额，但这种方法对绝缘样品有限制，对施加电场敏感，且块状灵敏度有限。相比之下，荧光产额方法没有这些限制，但一般发现其与吸收光谱存在偏差。我们证明，将检测限制在3s荧光通道（探测器处于特殊角度，所有偏振的贡献相等）可恢复所有3d金属L边的真实X射线吸收光谱。这些理论推导结果可通过核心激发态中缺乏3s - 3d相互作用来解释。比较线性和圆偏振光在任意检测几何结构下的X射线吸收与3s - PFY，会出现偏差，偏差可能高达15%。
