同步辐射XANES方法对FeCl_3水溶液的研究

Investigation of Fe^(3+) in FeCl_3 aqueous solution by XANES technique

利用X射线近边吸收谱学(X-ray Absorption Near Edge Structure,XANES)方法研究了不同浓度的FeCl3水溶液中Fe3+离子的电子结构和近邻结构.在不同浓度的FeCl3水溶液的XANES谱中,XANES谱的形状随着FeCl3浓度的不同而发生改变.在XANES谱的边前结构中观测到边前锋的分裂,其分裂的能量差约为1.6eV,随着浓度的降低约有0.2eV的高能方向的位移,此边前结构由1s-3d轨道的电子跃迁引起,双峰分裂来源于配位体配位引起的3d轨道分裂.随着FeCl3浓度的改变,XANES谱的主峰也发生变化,此变化来源于溶液中Fe—Cl配位与Fe—O配位的比例变化.另外,利用量子化学计算的方法对于Fe3+与不同数目的H2O和Cl?配位体络合时的构型进行了计算,得到了Fe3+在水溶液中近邻结构的信息,从另一方面解释了FeCl3溶液中Fe3+离子3d轨道分裂能的变化.

Electron structures and local atomic structures of Fe3＋ in different FeCl3 aqueous solution have been studied by X-ray absorption near edge structure （XANES） technique. The result shows that XANES spectra are different when the concentration of FeCl3 aqueous solution has been changed. Pre-edge regions of XANES spectra show a fine structure corresponding to a 1s to 3d transition of Fe atom, which is a double peak structure. Splitting energy of the double peak is about 1.6ev, and there is a 0.2ev shift to high-energy direction with concentration decreasing. Main peaks of XANES spectra of different FeCl3 aqueous solution are different, which attribute to different proportion of Fe—Cl bonds and Fe—O bonds. A calculation of complex Fe3＋ cation with different number of H2O and Cl- has been performed by computational method of quantum chemistry.