Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, CHN F23.2 Universitätstrasse 16, 8092 Zürich, Switzerland.
J Phys Chem A. 2009 Nov 5;113(44):12171-8. doi: 10.1021/jp902604p.
Pre-edge spectral features below the main X-ray absorption K-edge of transition metals show a pronounced chemical sensitivity and are promising sources of structural information. Nevertheless, the use of pre-edge analysis in applied research is limited because of the lack of definite theoretical peak-assignments. The aim of this study was to determine the factors affecting the chromium K-pre-edge features in trivalent chromium-bearing oxides and oxyhydroxides. The selected phases varied in the degree of octahedral polymerization and the degree of iron-for-chromium substitution in the crystal structure. We investigated the pre-edge fine structure by means of high-energy-resolution fluorescence detected X-ray absorption spectroscopy and by 1s2p resonant X-ray emission spectroscopy. Multiplet theory and full multiple-scattering calculations were used to analyze the experimental data. We show that the chromium K-pre-edge contains localized and nonlocalized transitions. Contributions arising from nonlocalized metal-metal transitions are sensitive to the nearest metal type and to the linkage mode between neighboring metal octahedra. Analyzing these transitions opens up new opportunities for investigating the local coordination environment of chromium in poorly ordered solids of environmental relevance.
过渡金属主 X 射线吸收边以下的预边缘谱特征具有显著的化学敏感性，是结构信息的有前途的来源。然而，由于缺乏明确的理论峰分配，预边缘分析在应用研究中的应用受到限制。本研究的目的是确定影响三价铬氧化物和氢氧化物中铬 K 预边缘特征的因素。所选相在八面体聚合度和晶体结构中铬代铁的程度上有所不同。我们通过高能分辨荧光探测 X 射线吸收光谱和 1s2p 共振 X 射线发射光谱研究了预边缘精细结构。我们使用多体理论和全多次散射计算来分析实验数据。结果表明，铬 K 预边缘包含局域和非局域跃迁。非局域金属-金属跃迁的贡献对最近的金属类型和相邻金属八面体之间的连接模式敏感。分析这些跃迁为研究环境相关无序固体中铬的局部配位环境提供了新的机会。
