Combining X-ray K$β_{1,3}$, valence-to-core, and X-ray Raman spectroscopy for studying Earth materials at high pressure and temperature: the case of siderite

X-ray emission and x-ray Raman scattering spectroscopy are powerful tools to investigate thelocal electronic and atomic structure of high and low Z elements in-situ. Notably, these methodscan be applied for in-situ spectroscopy at high pressure and high temperature using resistively orlaser-heated diamond anvil cells in order to achieve thermodynamic conditions which are presentin the Earth’s interior. We developed a setup for combined x-ray emission and x-ray Raman scatteringstudies at beamline P01 of PETRA III using a portable wavelength-dispersive von Hamosspectrometer together with the permanently installed multiple-analyzer Johann-type spectrometer.The capabilities of this setup discussed through the investigation of are exemplified by investigatingthe iron spin crossover of siderite FeCO$_3$ up to 49.3GPa by measuring the Fe M$_{2,3}$-edgeand Fe Kβ$_{1,3}$ emission line simultaneously. With this setup, the Fe valence-to-core emission canbe detected simultaneously with the Kβ$_{1,3}$ emission line providing complementary information onthe sample’s electronic structure. By implementing a laser-heating device, we demonstrate thestrength of using a von Hamos type spectrometer for spin state mapping at extreme conditions.Finally, we give different examples of low Z elements’ absorption edges relevant for applicationin geoscience that are accessible with the Johann-type XRS spectrometer. This setup providesa unique combination to gain new insights of the spin transition and compression mechanismsof Earth’s mantle materials of importance for comprehension of the macroscopic physical andchemical properties of the Earth’s interior