Development of micro-XANES mapping in the diamond anvil cell

Energy-dispersive X-ray absorption spectroscopy is now a well established method that has been applied to a broad range of applications. At the energy-dispersive EXAFS beamline of the ESRF, ID24, the recently achieved 5 × 5 µm focal spot combined with fast acquisition has allowed complex and non-uniform samples to be mapped and images to be obtained where each pixel contains full XAS information. This method has been applied to a study under extreme conditions of pressure and temperature in a diamond anvil cell in transmission mode. The case study was the investigation of the Fe K-edge XANES of (Mg,Fe)SiO₃-perovskite and (Mg,Fe)O-ferropericlase on decomposition of the spinel-structured olivine [γ-(Mg,Fe)₂SiO₄] at 78 (3) GPa after laser heating at 2200 (100) K.