Source: New York Times
With gentle pulses from gigantic lasers, scientists at Lawrence Livermore National Laboratory in California transformed hydrogen into droplets of shiny liquid metal.
Their research, reported on Thursday in the journal Science, could improve understanding of giant gas planets like Jupiter and Saturn whose interiors are believed to be awash with liquid metallic hydrogen.
The findings could also help settle some fractious debates over the physics of the lightest and most abundant element in the universe.
At the temperatures and pressures found at the surface of Earth, hydrogen atoms pair up in molecules and bounce around as a colorless gas.
At ultracold temperatures, below -423 degrees Fahrenheit, hydrogen condenses into a liquid. It also turns into a liquid at higher temperatures when squeezed under immense pressure. The molecules remain intact, and this state of liquid hydrogen is an insulator — a poor conductor of electricity.
Under even higher pressures, the molecules break apart into individual atoms, and the electrons in the atoms are then able to flow freely and readily conduct electricity — the definition of a metal.
An experiment at the Livermore lab in the 1990s was the first to convincingly create metallic hydrogen using a gas gun to send monstrous pressure waves through samples of hydrogen. But those tests did not reveal all of the details about how the transition occurred.
In recent years, researchers have figured out additional ways to make liquid metallic hydrogen. Isaac F. Silvera, a professor of physics at Harvard, and his colleagues used two interlocking pieces of diamond to compress a smidgen of hydrogen and then heated it with laser pulses. At Sandia National Laboratories in Albuquerque, intense bursts of magnetic fields were used to compress samples of deuterium, a heavier form of hydrogen.
The Sandia scientists reported that the metallic transition occurred at about 44 million pounds per square inch, or about 3 million times the atmospheric pressure at ground level on Earth. That was considerably higher than many had expected.
“There’s been a kind of confusion of predictions,” said Peter M. Celliers, a physicist at the Livermore lab who is the lead author of the new paper.
Experiments on matter at ultrahigh pressure are difficult to perform, often with conflicting results, which “made for a picture that has looked to date fairly muddled,” Dr. Celliers said. “We think it’s starting to clear up with this new data set.”
The new research is…
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