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The Laboratory
in the News

Discovery of new superheavy elements 113 and 115
The two newest superheavy elements, 113 and 115, were recently discovered through a collaborative effort between researchers from the Joint Institute for Nuclear Research (JINR) in Russia and scientists from Livermore’s Glenn T. Seaborg Institute and the Chemistry and Materials Science Directorate.
In experiments conducted between July 14 and August 10, 2003, at the JINR U400 cyclotron with the Dubna gas-filled separator, the team of scientists observed atomic decay patterns, or chains, that confirm the existence of elements 113 and 115. In these decay chains, element 113 is produced via the alpha decay of element 115. Energy Secretary Spencer Abraham says, “These elemental discoveries underscore both the value of federally supported basic research and the benefit of unfettered international scientific collaboration.”
The experiments produced four atoms each of element 113 and element 115 through the fusion reaction of calcium-48 nuclei impinging on an americium-243 target. The team observed three similar decay chains consisting of five consecutive alpha decays, which combined took less than 30 seconds and terminated in a spontaneous fission of an element-105 (dubnium) isotope with a very long half-life (16 hours). Results from the team’s research are featured in the February 2, 2004, issue of Physical Review C.
Joshua Patin, Livermore’s primary data analyst on the team, says the three similar decay patterns were a “positive identifier that something good had been seen, because the long decay chains just don’t happen that often.” Scientists at Livermore and JINR independently verified the data.
Contact: Joshua Patin (925) 422-6341 (patin1@llnl.gov).

Details of water-to-air interface revealed
Using the Laboratory’s terascale computers, Livermore scientists have revealed details of the reactive states and faster relaxation of molecules at the interface of water and air. Christopher Mundy and I-Feng Kuo created the first ab initio simulations of a stable liquid–air interface. Ab initio simulations present an unbiased representation of water in different environments and are ideal for explaining surface conditions.
The data analysis shows a faster relaxation of water molecules at the interface and reveals that the surface contains far more reactive states than the bulk water. “These simulations serve as an important step toward the use of terascale resources to produce simulations of water in complex environments,” says Mundy.
In addition, the models successfully captured surface phenomena of water recently observed experimentally by Professor Richard Saykally’s group at the University of California at Berkeley. A paper describing this work appeared in the January 30, 2004, issue of Science.
Contact: Christopher Mundy (925) 422-9571 (mundy2@llnl.gov).

Scientists unveil melting point of iron at Earth's core
Livermore physicists Jeffrey Nguyen and Neil Holmes have discovered that iron at conditions comparable to Earth’s core melts at a pressure of 225 gigapascals and a temperature of about 5,100 kelvins. Determining the melting point of iron is essential to determining the temperatures at core boundaries and the crystal structure of Earth’s solid inner core. To date, the properties of iron at high pressure have been investigated experimentally through both laser-heated, diamond-anvil cell experiments and shock-compression techniques as well as through theoretical calculations.
However, those techniques have not produced a consensus on the melt line or the high-pressure, high-temperature phase of iron in the inner core. Using the Laboratory’s two-stage gas gun, the researchers demonstrated that a shocked sample of iron crosses the melt line at a pressure between that of the core–mantle boundary and the pressure of the inner–outer core boundary.
“By determining the melting point of iron, we can estimate the temperature at the core boundaries,” Nguyen said. “These data provide us with more information to study the temperature of Earth’s core.” Nguyen and Holmes’s results appeared in the January 22, 2004, issue of Nature.
Contact: Jeffrey Nguyen (925) 423-6838 (nguyen29@llnl.gov).

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UCRL-52000-04-4 | April 6, 2004