X-Ray Diffraction of Shock Compressed H2O

Wednesday, 17 December 2014
Arianna E Gleason, Stanford University, Los Altos Hills, CA, United States
H2O, critical for life and ubiquitous in biology, is one of the most abundant molecules in the solar system and is relevant to many fields, including fundamental physics and chemistry. Phase transformation information of H2O is also important to applied areas like planetary science where it is a constituent of giant planets Neptune and Uranus, icy satellites (e.g., Europa, Ganymede), and extrasolar planets (icy “super-Earths”). Using the MEC (Matter in Extreme Conditions) hutch at LCLS, we reach simultaneous high pressure (P) and temperature (T) with laser-driven shock waves and the capability of taking snapshots during a dynamic process with the X-ray Free Electron Laser (xFEL). We report the only shock-driven diffraction data on H2O ever collected to date, and examine time-resolved diffraction from ice Ih to high pressure ice VII. At 2 Mbar we find evidence of ice X – this has significant implications for planetary interiors and providing a bound for the onset of the superionic phase.