X-ray absorption near-edge structure at the LI–III thresholds of Pr, Nd, Sm, and Dy compounds with unusual valences
X-ray absorption near-edge structure at the LI–III thresholds of Pr, Nd, Sm, and Dy compounds with unusual valences
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DOI：
10.1016/s0925-8388(96)02473-5
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发表时间：
1997-01
影响因子：
6.2
通讯作者：
Zhiwei Hu;G. Kaindl;G. Meyer
中科院分区：
文献类型：
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作者：
Zhiwei Hu;G. Kaindl;G. Meyer
对稀土元素 Pr、Nd、Sm 和 Dy 以及 Sm3S4 的还原卤化物在稀土 LI-III 阈值处的 X 射线吸收近边缘结构 (XANES) 进行了系统研究。对于二价卤化物 NdCl2、SmCl2、DyBr2 以及混合价化合物 NaNd2Cl6、Sm3S4 和 K5Dy3I12，观察到“白线”(WL)，对应于二价 Ln 元素 4f 配置的核心激发态。形式上的混合价 Pr 卤化物 NaPr2Cl6、Pr2Br5 和 PrCl2.33 被发现仅包含与 PrIII 的 4f2 构型相对应的 WL。除了不同 4f 构型（化合价）引起的显着能量变化外，具有相同化合价但不同卤素配体的化合物的 XANES WL 表现出 L1 中的化学位移远大于 LIIIXANES 光谱中的化学位移。这种显着差异可以根据 Ln/配体共价随配体原子电负性的变化进行定性解释。
The X-ray absorption near-edge structure (XANES) at the lanthanide LI–IIIthresholds was studied systematically for reduced halides of the lanthanide elements Pr, Nd, Sm, and Dy, as well as for Sm3S4. For the divalent halides NdCl2, SmCl2, DyBr2, as well as for the mixed-valent compounds NaNd2Cl6, Sm3S4, and K5Dy3I12, ‘white lines’ (WLs), corresponding to core-excited states with the 4f configurations of divalent Ln elements, were observed. The formally mixed-valent Pr halides NaPr2Cl6, Pr2Br5, and PrCl2.33were found to contain only WLs corresponding to the 4f2configuration of PrIII. In addition to the substantial energy shifts caused by different 4f configurations (valences), the XANES WLs of compounds with the same valence but different halogen ligands exhibit chemical shifts which are far larger in L1than in LIIIXANES spectra. This striking difference is qualitatively explained on the basis of changes of the Ln/ligand covalence as a function of the electronegativity of the ligand atoms.