Ultrafast X-ray Studies on the Dynamics of Transitions in Geophysical Materials
(SLAC Standford University)
Room. E1.173 (European XFEL, main building)
European XFEL, main building
Understanding the processes which dictate physical properties in condensed matter, such as strength, elasticity, plasticity, and the kinetics of phase transformation/crystallization, requires studies at the relevant length-scales (e.g., interatomic spacing and grain size) and time-scales (e.g., phonon period). Experiments performed at the Matter in Extreme Conditions end-station at the Linac Coherent Light Source, SLAC combine a laser-driven dynamic compression pump and X-ray free electron laser (XFEL) probe. We present time-resolved structural and/or electronic transformations in a suite of geophysical materials. SiO2 (quartz/fused silica), a major component of the Earth’s crust, is seen to undergo a rapid transformation (within 2 nanoseconds) to a high-pressure polymorph (stishovite) on shock compression and reversion to an amorphous state on shock release. Divorcing the onset of an electronic vs. structural transition in materials at extreme conditions is now possible with single-shot X-ray emission spectroscopy as evidenced by simultaneous electronic spin-transition and structural phase transition data collected on a Fe-bearing silicate, bridgemanite. This mineral, composing 40% of the Earth’s mantle. Deformation mechanism and strength models of iron at near inner core conditions have significant implications for planetary evolution over a pressure range of a few to hundreds of GPa. Taking advantage of the brilliance and coherence of XFEL technology coupled with a dynamic driver provides an experimental platform that takes us to the frontier in condensed matter physics.