NON-RESONANT X-RAY RAMON SCATTERING AT HIGH PRESSURE

X-ray absorption spectroscopy (XAS) is a well established and widely used technique for probing, chemical bonding, valence and conduction electronic structures, electron correlations and local coordination chemistry and structure. XAS measurements on low Z (first and second row) elements require soft x-rays resulting in significant limitations on the measurements since, only the near surface is probed (submicron), samples must be in vacuum or an atmosphere with very short path lengths and only low absorbing environments can be used precluding its use in high pressure research. Synchrotron based inelastic x-ray scattering (IXS) or X-ray Raman Scattering has opened up XAS to new fields by allowing samples made up of first and the second row elements to be studied while enclosed in absorbing environments. We have been developing and optimizing the technique at GSECARS for use with a DAC for the past six years allowing us to probe the coordination chemistry of elements such as Li, B, C, N, and O in crystalline and amorphous materials up to 60 GPa. Using this new tool we have for example explored; bonding changes in compressed superhard graphite, the formation of sp3 bonding in compressed boron nitride, and bonding changes in borate glasses. I will present the details of the GSECARS beamline x-ray optics, six element analyzer and diffractometer and software interface, that allow us to perform these difficult measurements, highlighting past, present and future research.