Chemical Sensitivity of Kβ and Kα X-ray Emission from a Systematic Investigation of Iron Compounds
Chemical Sensitivity of Kβ and Kα X-ray Emission from a Systematic Investigation of Iron Compounds
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DOI：
10.1021/acs.inorgchem.0c01620
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发表时间：
2020-09-08
影响因子：
4.6
通讯作者：
Glatzel, Pieter
中科院分区：
文献类型：
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作者：
Lafuerza, Sara;Carlantuono, Andrea;Glatzel, Pieter
钾荧光X射线发射光谱(XES)研究局域自旋在自然科学的各个领域都受到了越来越多的关注。Kβ(Kα)XES的自旋敏感性来源于未成对的3p(2p)和3d电子之间的交换作用，Kβ的自旋敏感性大于Kα。我们对大量的含铁化合物进行了深入的研究。根据常用的定量参数(Kβ(1，3)一阶矩、Kα、半峰全宽和积分绝对差Iad-)对实验光谱进行了分析，并仔细检查了差谱。还进行了多重计算，以阐明导致化学敏感性的潜在机制。我们的结果证实了共价性对Kβ和Kα谱线都有很强的影响。我们建立了一个可靠的KβXES的自旋灵敏度，因为它是由交换作用控制的，它的变化可以用Kβ(1，3)一阶矩或KβIAD来量化，并导致系统的不同信号线形状。在Fe~(3+)和Fe~(2+)在水溶液中的KβXES谱中，我们发现了一种新的差谱，这种差谱不能通过尺度交换积分来再现。我们用价轨道间轨道混合的强烈差异来解释这一现象。这一结果要求在没有仔细分析谱线形状的情况下解释由于自旋变化而引起的KβXES光谱变化时要谨慎。对于KαXES，较小的交换相互作用和其他电子相互作用的影响使得提取与自旋直接相关的量变得困难。
K-fluorescence X-ray emission spectroscopy (XES) is receiving growing interest in all fields of natural sciences to investigate the local spin. The spin sensitivity in K beta (K alpha) XES stems from the exchange interaction between the unpaired 3p (2p) and the 3d electrons, which is greater for K beta than for K alpha. We present a thorough investigation of a large number of iron-bearing compounds. The experimental spectra were analyzed in terms of commonly used quantitative parameters (K beta(1,3) -first moment, K alpha, full width at half-maximum, and integrated absolute difference -IAD-), and we carefully examined the difference spectra. Multiplet calculations were also performed to elucidate the underlying mechanisms that lead to the chemical sensitivity. Our results confirm a strong influence of covalency on both K beta and K alpha lines. We establish a reliable spin sensitivity of K beta XES as it is dominated by the exchange interaction, whose variations can be quantified by either K beta(1,3)-first moment or K beta-IAD and result in a systematic difference signal line shape. We find an exception in the K beta XES of Fe3+ and Fe2+ in water solution, where a new difference spectrum is identified that cannot be reproduced by scaling the exchange integrals. We explain this by strong differences in orbital mixing between the valence orbitals. This result calls for caution in the interpretation of K beta XES spectral changes as due to spin variations without a careful analysis of the line shape. For K alpha XES, the smaller exchange interaction and the influence of other electron electron interactions make it difficult to extract a quantity that directly relates to the spin.