EXAFS studies under high pressure by X-ray Raman scattering

We discuss extended X-ray absorption fine structure (EXAFS) measurements on light element compounds under high pressure. An absorption edge in light elements, 2keV in energy, is measured by X-ray Raman scattering using 20keV X-rays. To enhance the intensity, a large-culet, sintered polycrystalline diamond anvil cell is used, so that a scattering volume is maximized. For a pressure monitor, diffraction lines from NaCl powders compressed together with the sample are measured through an X-ray Raman spectrometer. With this set-up, we have measured EXAFS features at the oxygen K-edge in MgSio(3) glass up to 30GPa. As the pressure increases, the oscillation pattern drastically changes, associated with the densification of the glass.