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Aiming for superheavy elements.



When a light atomic nucleus smashes into a much heavier one, the two particles occasionally stick together to create a new element. Using such a strategy, researchers have synthesized more than two dozen elements having higher atomic numbers than that of uranium, which has 92 protons in its nucleus. Typically, these new elements survive for just fractions of a second before they radioactively decay or fission fission, in physics: see nuclear energy and nucleus; see also atomic bomb.  into isotopes of other elements.

Now, a team of physicists has discovered two new isotopes of element 106, seaborgium seaborgium (sēbôr`gēəm), artificially produced radioactive chemical element; symbol Sg; at. no. 106; mass number of most stable isotope 266; m.p., b.p., sp. gr., and valence unknown.  (SN: 3/19/94, p.180). One isotope has an atomic mass of 265 (having 159 neutrons in its nucleus), and the other has an atomic mass of 266 (having 160 neutrons in its nucleus). The isotopes take longer to decay than expected, suggesting that these particular combinations of protons and neutrons in a nucleus have an enhanced stability.

Yuri A. Lazarev of the Joint Institute for Nuclear Research The Joint Institute for Nuclear Research, JINR (Russian: Объединённый институт ядерных  in Dubna, Russia, Ronald W. Lougheed of the Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory: see Lawrence Berkeley National Laboratory.

(body) Lawrence Livermore National Laboratory - (LLNL) A research organaisatin operated by the University of California under a contract with the US Department of Energy.
 in Livermore, Calif., and their collaborators report the discovery in the Aug. 1 PHYSICAL REVIEW LETTERS Physical Review Letters is one of the most prestigious journals in physics.[1] Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. .

The researchers created these rare isotopes by hurling neon-22 nuclei into curium-248. One product, seaborgium-265, has a half-life (the time it takes for half of a sample to decay) between 2 and 30 seconds; seaborgium-266 has a half-life between 10 and 30 seconds. These half-lives are at least 10 times longer than those previously observed for a seaborgium isotope.

Theorists attribute the enhanced stability of these isotopes to a slight deformation of the nuclei from a spherical to an oval shape. They predict a stronger deformation and even greater stability for a nucleus with atomic number 108 and mass number 270.

"The remarkable influence seen here of small shape changes on nuclear properties will undoubtedly stimulate modeling of new nuclear shapes," Arthur N. James of the University of Liverpool The University of Liverpool is a university in the city of Liverpool, England. History

The University was established in 1881 as University College Liverpool, admitting its first students in 1882.
 in England comments in the Sept. 8 NATURE.

Meanwhile Lazarev and his coworkers are bombarding uranium with sulfur nuclei to create what they hope will be new, longer-lived isotopes of element 108, hassium hassium (hăs`ēəm, häs`–), artificially produced radioactive chemical element; symbol Hs; at. no. 108; mass number of most stable isotope 265; m.p., b.p., sp. gr., and valence unknown. .
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Title Annotation:new isotopes of seaborgium discovered
Publication:Science News
Article Type:Brief Article
Date:Sep 24, 1994
Words:344
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