Heaviest Element Lumbers Into View

Rich oversees Science's international coverage.

The race to capture one of the biggest prizes in nuclear physics--an exceptionally long-lived superheavy element--appears to be over. In a cautiously worded e-mail to a close-knit group vying for the trophy atom, scientists at the Joint Institute for Nuclear Research in Dubna, near Moscow, this month unveiled evidence for the creation of a nucleus with 114 protons--the heaviest element yet forged.

If confirmed, the sighting would mean far more than just another entry in the periodic table. Element 114 appears to last for 30 seconds before decaying, a longevity that would verify predictions of an "island of stability" beyond the lighter, less stable nuclei glimpsed earlier. "This is the most exciting event in our lives," says Albert Ghiorso of the Lawrence Berkeley National Laboratory in California, who has spent 35 years hoping his group would plant the flag on the fabled terrain.

For a half-century physicists have used nuclear reactors and particle accelerators to forge new elements, beyond the 94 known to exist in nature. Like climbing taller and taller peaks, each successive effort has required vastly more energy and greater technological legerdemain. And for ever-more fleeting results: Although some transuranic isotopes last for years, an isotope of the last element created--number 112--is so unstable it sticks around a mere 280 microseconds. Theorists have predicted, however, that this trend toward instability would be reversed as additional protons and neutrons fill out nuclear shells. With a full shell of protons, element 114 should lie well within the stable island.

For several weeks late last year, a team led by Dubna's Yuri Oganessian and Vladimir Utyonkov pounded a plutonium-244 target with some 5 × 1018 atoms of a rare calcium isotope, calcium-48. Sifting the data from their detector, the researchers and their collaborators at Lawrence Livermore National Laboratory in California spotted what appears to be the unique signature of a decay chain starting with 289114, which hung around for 30 seconds before hiccuping an alpha particle to form an isotope of 112.

More work is needed to confirm the find, says Ghiorso, whose group will do follow-up studies. In a sad footnote, isotope pioneer Glenn Seaborg, 86, suffered a crippling stroke a few months ago and may not comprehend the news, says Ghiorso. Seaborg, whose name graces element 106, would be thrilled by a discovery that, if verified, would open a terra incognita for nuclear science.

Posted in Physics