X-ray Absorption Fine Structure at the Cesium L3 Absorption Edge for Cesium Sorbed in Clay Minerals

Abstract

We present the use of near-edge X-ray absorption fine structure (NEXAFS) to investigate local electronic structures of cesium ions sorbed in two types of clay minerals (vermiculite and kaolinite) with a different capacity to fix Cs. NEXAFS is element-specific because X-ray absorption edges of different elements have different energies. However, the energy of the Cs L3 absorption edge is close to that of the K-edge of titanium generally contained in clay minerals. Therefore, Cs L3-edge NEXAFS measurements of Cs in clay minerals have not yet succeeded. In this study, we confirmed the peak intensity between vermiculite and kaolinite in the Cs L3-edge NEXAFS spectra by separately monitoring T Kα and Cs Lα fluorescence X-rays. To clarify the identification of NEXAFS spectra, theoretical calculations were performed using the discrete variational Xα molecular orbital method (DV-Xα), and peak identification was achieved. The difference in peak intensity was explained by the difference in the electron density of u...