Metallic Hydrogen :: essays research papers fc

Hydrogen: the most abundant element in the universe. Normally it has been considered to remain a non-metal at any range of temperatures and pressures. That is, until now. Recently this year, hydrogen was changed into a metallic substance, which could conduct electricity. An experiment conducted by William J. Nellis et al. at the Lawrence Livermore National Laboratory accomplished this feat. Hydrogen was converted from a non-metallic liquid, into a liquid metal. The likelihood that the most abundant element in the universe could be converted into metallic form at sufficient pressures was first theorized in 19351, but tangible evidence has eluded scientists in the intervening decades. "Metallization of hydrogen has been the elusive Holy Grail in high-pressure physics for many years," said Bill Nellis, one of three Livermore researchers involved in the project. "This is a significant contribution to condensed matter physics because a pressure and temperature that actually produce metallization have finally been discovered."2 Livermore researchers Sam Weir, Art Mitchell, and Bill Nellis used a two-stage gas gun at Livermore to create enormous shock pressure on a target containing liquid hydrogen cooled to 200 K (- 4200 F). Sam Weir, Arthur Mitchell (a Lab associate), and Bill Nellis published the results of their experiments in the March 11 issue of Physical Review Letters under the title "Metallization of Fluid Molecular Hydrogen at 140 GPa (1.4 Mbar)." When asked about the significance of the work, Nellis had this to say: "Hydrogen makes up 90 percent of the universe. Jupiter is 90 percent hydrogen and contains most of the mass in our planetary system. Hydrogen is very important to a lot of work done at the Lab. Hydrogen in the form of deuterium and tritium isotopes is the fuel in laser-fusion targets and how it behaves at high temperatures and pressures is very important to Nova and the National Ignition Facility."3 By measuring the electrical conductivity, they found that metallization occurs at pressure equivalent to 1.4 million times Earth's atmospheric pressure, nine times the initial density of hydrogen, and at a temperature of 30000 K (50000 F). Because of the high temperature, the hydrogen was a liquid. The intense pressure lasted less than a microsecond. Optical evidence of a new phase of hydrogen has been previously reported using an experimental approach that involves crushing microscopic-sized samples of crystalline hydrogen between diamond anvils.4 However, metallic character has not been established. Metallic character is most directly established by electrical conductivity measurements which are not yet possible in diamond anvil cells at these pressures. The Livermore team's results were surprising because of their methods, the form of hydrogen used and the pressure needed to achieve the result (which was much lower than previously believed). Virtually all predictions surrounding metallic hydrogen have been made for solid hydrogen at