Two New Elements Made: Atom smashups yield 113 and 115

Peter Weiss

Last summer, when more than 8 million trillion calcium ions blasted a thin film of americium atoms nonstop for more than a month, the collisions generated four atoms of never-before-seen element 115, a Russian-U.S. team now reports.

Each of those putative atoms of element 115 disintegrated within fractions of a second by spontaneously ejecting an alpha particle, which contains two protons and two neutrons. Therefore, the experiment appears to have also produced the first four atoms of element 113 ever recognized.

In the Feb. 1 Physical Review C, researchers of the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, and Lawrence Livermore (Calif.) National Laboratory (LLNL) detail these new findings. Adding to previous results dating to late 1998, the Dubna-Livermore team has single-handedly chalked up evidence of all the elements from 113 to 118 (SN: 2/6/99, p. 85: http://www.sciencenews.org/pages/sn_arc99/2_6_99/fob4.htm; 7/20/02, p. 37: Available to subscribers at http://www.sciencenews.org/articles/20020720/fob5.asp).

"It's very spectacular. You just have to say, 'Wow!'," comments nuclear chemist Walter D. Loveland of Oregon State University in Corvallis.

The new findings, which have yet to be confirmed by other laboratories, tentatively add two entries to the periodic table of the chemical elements. Because the lifetimes of these atoms—up to 1.2 seconds for element 113—are lengthy for atoms of such high masses, the findings give credence to a long-standing notion that there are many so-called superheavy elements yet to be created that could prove to be much longer-lived, says LLNL chemist Kenton J. Moody, a member of the team.

Since the 1960s, nuclear chemists have theorized that superheavy elements with lifetimes of hours, days, or even longer are possible. Such jumbo atoms could provide a rich testing ground for currently inaccessible realms of chemistry and nuclear physics.

To create elements 113 and 115, Yuri Ts. Oganessian and his colleagues of JINR accelerated neutron-rich calcium-48 ions in a circular particle accelerator and then steered them into a spinning, saucer-size ring of americium-coated titanium foil. Calcium is element 20, and the human-made element americium is 95.

To determine what atoms were created by calcium-americium fusions and what formed from the subsequent decays of these atoms, groups of analysts at Dubna and Livermore each separately interpreted readings from detectors struck by the newly made particles.

Loveland says that such dual scrutiny has reassured other heavy-element scientists made cautious by the 1999 false claim of scientists at Lawrence Berkeley (Calif.) National Laboratory that they had discovered elements 116 and 118 (SN: 8/4/01, p. 68: Available to subscribers at http://www.sciencenews.org/articles/20010804/fob2.asp).

Still, none of the many Dubna-Livermore findings can be considered rock-solid until other laboratories have confirmed them, Loveland cautions.

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References:

Oganessian, Y.Ts. … K.J. Moody … M.A. Stoyer, et al. 2004. Experiments on the synthesis of element 115 in the reaction ²⁴³Am(⁴⁸Ca,xn)^291-x115. Physical Review C 69(Feb. 1):021601. Abstract available at http://dx.doi.org/10.1103/PhysRevC.69.021601.

Further Readings:

Gorman, J. 2001. Researchers take an element off the table. Science News 160(Aug. 4):68. Available to subscribers at http://www.sciencenews.org/articles/20010804/fob2.asp.

Peterson, I. 1999. Glimpses of a superheavy element. Science News 156(Oct. 30):287. References and sources available at http://www.sciencenews.org/pages/sn_arc99/10_30_99/note10ref.htm.

Weiss, P. 2002. Heavy suspicion: Elemental discoveries trace to fake data. Science News 162(July 20):37–38. Available to subscribers at http://www.sciencenews.org/articles/20020720/fob5.asp.

______. 1999. New elements pop in, cousins may linger. Science News 155(June 12):273. Available at http://www.sciencenews.org/pages/sn_arc99/6_12_99/fob2.htm.

______. 1999. New element leaves lightweights behind. Science News 155(Feb. 6):85. Available at http://www.sciencenews.org/pages/sn_arc99/2_6_99/fob4.htm.

For further information on superheavy elements, go to http://www-cms.llnl.gov/e113_115/about.html (Lawrence Livermore National Laboratory).

Sources:

Kenneth Gregorich
Lawrence Berkeley National Laboratory
1 Cyclotron Road
Mailstop 88R0192
Berkeley, CA 94720

Sigurd Hofmann
Gesellschaft für Schwerionenforschung mbH
Planckstrasse 1
64291 Darmstadt
Germany

Walter D. Loveland
Department of Chemistry
Oregon State University
153 Gilbert Hall
Corvallis, OR 97331-4003

Kenton J. Moody
University of California, Livermore
Lawrence Livermore National Laboratory
Livermore, CA 94551

Yuri Ts. Organessian
Joint Institute for Nuclear Research
141980 Dubna
Russian Federation

Mark A. Stoyer
University of California, Livermore
Lawrence Livermore National Laboratory
Livermore, CA 94551

From Science News, Volume 165, No. 6, February 7, 2004, p. 84.