X-ray absorption spectroscopy at high pressures

The authors report X-ray absorption measurements on several binary compounds, CuBr, SmS, ZnSe, KBr and RbCl at high pressures using synchrotron radiation. Included are those features within 50 eV above an X-ray edge, the XANES (X-ray Absorption Near Edge Structure), as well as the region, 50 eV to 1000 eV above, namely the EXAFS (Extended X-ray Absorption Fine Structure). Both regions show a marked pressure dependence, especially when the sample undergoes a pressure induced phase transition. The XANES indicates the changing electronic structure, whereas the EXAFS clearly indicates the changing bond lengths and atom-pair mean-square displacements. Both features have proven to be useful for internal pressure calibration. (Auth.)