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The Laboratory
in the News

Discovery of element 118
Scientists from the Chemistry, Materials, and Life Sciences Directorate in collaboration with researchers from the Joint Institute for Nuclear Research (JINR) in Russia have discovered element 118, the newest superheavy element. In experiments conducted at the JINR U400 cyclotron between February and June 2005, the researchers observed atomic decay patterns, or chains, that establish the existence of element 118.
The experiments yielded three atoms of element 118 by bombarding a californium target with calcium ions. The team observed the alpha decay from element 118 to element 116 and then to element 114. The Livermore–Dubna team had created the same isotope of element 116 in earlier experiments. This discovery brings the total to five new elements for the Livermore–Dubna collaboration (113, 114, 115, 116, and 118). The results were published in the October 9, 2006, edition of Physical Review C.
Contact: Ken Moody (925) 423-4585 (moody3@llnl.gov).

Scientists crack open stellar evolution
Using three-dimensional models run on some of the fastest computers in the world, Laboratory physicists have created a mathematical code that cracks a mystery surrounding stellar evolution. For years, physicists have theorized that low-mass stars (about one to two times the size of the sun) produce great amounts of helium-3 (3He). When low-mass stars exhaust the hydrogen in their cores to become red giants, most of their matter is ejected, substantially enriching the universe in this light isotope of helium. However, this enrichment when added to big bang predictions conflicts with observations. Assuming that nearly all stars were rapidly rotating, scientists theorized that stars destroy the 3He. However, even this theory failed to bring the evolution results into agreement with the big bang and observations.
Now, by modeling a red giant with a fully three-dimensional hydrodynamic code, Livermore researchers Peter Eggleton and David Dearborn identified the mechanism of how and where low-mass stars destroy the 3He produced during the stars’ evolution. They found that 3He burning in a region just outside of the helium core, previously thought to be stable, creates conditions that drive a newly discovered mixing mechanism. Bubbles of material, slightly enriched in hydrogen and substantially depleted in 3He, float to the surface of the star and are replaced by 3He-rich material for additional burning. In this way, the stars destroy their excess 3He, without requiring additional conditions such as rapid rotation. The research appears in the October 26, 2006, edition of Science Express.
Contact: David S. Dearborn (925) 422-7219 (dearborn2@llnl.gov) or Peter Eggleton (925) 423-0660 (eggleton1@llnl.gov).

Scientists capture nanoscale images with x-ray laser
Laboratory scientists have for the first time validated the idea of using extremely short and intense x-ray pulses to capture images of objects, such as proteins, before the x rays destroy the sample. At the same time, they also established a speed record of 25 femtoseconds for flash imaging. When even more powerful x-ray lasers are available, the new method will be applicable to atomic-resolution imaging of complex biomolecules. The technique will allow scientists to gain insight into the fields of materials science, plasma physics, biology, and medicine.
Using the free-electron laser at Deutsches Elektronen-Synchrotron in Hamburg, scientists, as part of an international collaboration led by Henry Chapman of Lawrence Livermore and Janos Hajdu of Uppsala University, were able to record a single diffraction pattern of a nanostructured object before the laser destroyed the sample. A Livermore-developed computer algorithm then used the recorded diffraction pattern to re-create an image of the object. This imaging technique could be applied to atomic-resolution imaging because it does not require a high-resolution lens. The flash images could resolve features 50 nanometers in size, which is about 10 times smaller than what is achievable with an optical microscope. The research appeared in the November 12, 2006, online edition of Nature Physics.
Contact: Henry Chapman (925) 423-1580 (chapman9@llnl.gov).



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UCRL-52000-07-1/2 | January 12, 2007