International team fills gap in the periodic table
Editor’s Note: Additional material was added to this story at 5 p.m. on April 6, 2010.
Physicists have reported synthesizing element 117, the latest achievement in their quest to create “superheavy” elements in the laboratory. A paper describing the discovery has been accepted for publication in Physical Review Letters.
A team led by Yuri Oganessian of the Joint Institute for Nuclear Research in Dubna, Russia, reports smashing together calcium-48 — an isotope with 20 protons and 28 neutrons — and berkelium-249, which has 97 protons and 152 neutrons. The collisions spit out either three or four neutrons, creating two different isotopes of an element with 117 protons.
Sigurd Hofmann, a nuclear physicist at the GSI research center in Darmstadt, Germany, calls the new work on element 117 “convincing.”
Most elements heavier than uranium, which has 92 protons, do not exist stably in nature and must