Inelastic x-ray scattering at ultrahigh pressures

Inelastic x-ray scattering (IXS) provides high-pressure research with an arsenal of analytical capabilities for key measurements that were previously unattainable, and high-pressure research provides IXS with numerous applications where the technique has unique advantages over other methods. High-pressure investigations can now be conducted using non-resonant IXS, resonant IXS, nuclear resonant IXS and x-ray emission spectroscopy with energy resolutions of 100 meV to 1 eV for electronic transitions and 1 to 10 meV for phonon studies. By pressure-tuning materials over a wide range, we are able to investigate fundamental properties of the electron gas, strongly correlated electron systems, high-energy electronic excitations and phonons in energy and momentum space. The results have important implications for a variety of materials problem applications as well as providing basic information for understanding the deep interior of the Earth and other planets.