Interpreting EXAFS Spectra: Toward Ramp-Compression Studies of Iron Oxide

Extended x-ray absorption fine structure (EXAFS) spectroscopy will be used to characterize iron oxide (FeO) ramp compressed to Mbar pressures. EXAFS spectroscopy provides information about the local structure, density, and temperature in compressed materials. The interpretation of the EXAFS spectral modulations was studied using ambient temperature FeO absorption data obtained with the Advanced Photon Source (APS) synchrotron[1] and theoretical predictions. The FeO data were evaluated by degrading the signal-counting statistics and background levels to understand how future spectrometer development will improve the data obtained in planned experiments at the Omega Laser Facility.[2] This analysis and spectrometer development will be applied to experiments using FeO compressed to conditions analogous to the Earth’s lower mantle and core in order to increase our understanding of the formation and evolution of the Earth and iron-rich exoplanets.

[1] XAFS Spectral Library, Spectrum: FeO data, 13 June 2018, http://cars.uchicago.edu/xaslib/spectrum/611.

[2] T. R. Boehly et al., Opt. Commun. 133, 495 (1997).