The illustration shows the combination of intense pressures and extreme temperatures produce by laser shockwaves, which caused the ice to assume an exotic superionic phase -- part ice, part liquid. Photo by Millot, Coppari, Hamel, Krauss / LLNL
May 9 (UPI) -- Scientists at the Lawrence Livermore National Laboratory successfully imaged the structure of superionic ice using giant lasers. Shockwaves produced by the laser caused the water to flash-freeze, while X-ray diffraction patterns revealed the atomic structure of the ice's exotic phase change.
Superionic ice is a unique phase that forms under extreme conditions, like the high pressure and frigid temperatures found on Uranus and Neptune. The phase features a solid lattice of oxygen and liquid-like hydrogen.
Using lasers and X-ray imaging, scientists for the first time revealed the formation process and inner structure of the exotic ice phase.
"We wanted to determine the atomic structure of superionic water," LLNL physicist Federica Coppari said in a news release. "But given the extreme conditions at which this elusive state of matter is predicted to be stable, compressing water to such pressures and temperatures and simultaneously taking snapshots of the atomic structure was an extremely difficult task, which required an innovative experimental design."
Models have long predicted the existence of superionic ice. Over the last few years, LLNL scientists have been working on various techniques for combining extreme pressures and temperatures using laser shockwaves to produce unusual phase changes in ice. Last year, scientists reported the first evidence of superionic ice in their test facilities at LLNL.
For the latest experiments, researchers used the giant lasers at the University of Rochester's Omega Laser Facility.
"We designed the experiments to compress the water so that it would freeze into solid ice, but it was not certain that the ice crystals would actually form and grow in the few billionths of a second that we can hold the pressure-temperature conditions," said LLNL physicist Marius Millot.
To image the crystallization process and the structure of the superionic ice, scientists directed additional laser pulses onto a small piece of iron foil, producing an intense flash of flash of X-rays.
"The X-ray diffraction patterns we measured are an unambiguous signature for dense ice crystals forming during the ultra-fast shockwave compression demonstrating that nucleation of solid ice from liquid water is fast enough to be observed in the nanosecond timescale of the experiment," Coppari said.
Last year's experiments only provided imprecise signature of superionic ice, but the latest efforts -- described this week in the journal Nature -- allowed scientists capture high-definition images of the exotic ice phase.
The new findings will help scientists improve the accuracy of computer simulations of superionic ice, as well as the models used to predict the composition and behavior of the interiors of ice giants like Uranus and Neptune.
"Because water ice at Uranus and Neptune's interior conditions has a crystalline lattice, we argue that superionic ice should not flow like a liquid such as the fluid iron outer core of the Earth," Millot said. "Rather, it's probably better to picture that superionic ice would flow similarly to the Earth's mantle, which is made of solid rock, yet flows and supports large-scale convective motions on the very long geological timescales."
