Using spectrally resolved x-ray scattering to elucidate chemistry and phase transitions in matter dynamically compressed to Mbar pressures

The HED-HIBEF instrument at European XFEL allows to create and probe matter dynamically compressed to Mbar pressures at unprecedented repetition rates and very high reproducibility. Data accumulation then enables previously inaccessible methods of photon-hungry x-ray spectroscopy methods for in situ characterization of the compressed states. This presentation will discuss inelastic X-ray scattering measurements with ~eV resolution from shock-compressed carbon and hydrocarbon samples. Our data provides insights into the electronic structure during the shock-induced transition of graphite or amorphous carbon to diamond and shows evidence for strong plastic work heating effects in shock compressed diamond resulting in temperatures far beyond those predicted by Hugoniot curves from commonly used equation of state tables. In dynamically compressed hydrocarbons we demonstrate the sensitivity for carbon-hydrogen phase separation and show first hints of inelastic x-ray scattering from isolated liquid metallic hydrogen.