Element 110 makes a very fleeting debut.
Researchers at GSI, the center for heavy ion research in Darmstadt, reported evidence last week of an isotope of element 110, with an atomic mass of 269. The atomic number indicates the number of protons in the atom, while its mass reveals the number of protons and neutrons.
The international team of scientists, led by GSI physicist Peter Armbruster, produced the element by bombarding an isotope of lead with nickel atoms. The two fused, producing an unstable, intermediate atom with an atomic number of 110 and a mass of 270.
That intermediate atom then ejected a neutron, stabilizing itself for 270 microseconds as the long-sought element 110 before undergoing a unique chain of decays. The researchers meticulously recorded the emission of four alpha-particles, each a helium nucleus with two protons and two neutrons.
Observing this distinct decay pattern -- as element 110 spawned daughter and granddaughter isotopes 108 to 102 -- permits researchers to confirm the presence of the parent element 110, says Armbruster.
To produce a single atom of element 110, the researchers used the UNILAC accelerator at GSI to bombard a target of lead over many days with more than a billion billion nickel atoms. A detector system searched each collision for element 110's distinct decay sequence. Armbruster and his 12 coworkers detected the new element on Nov. 9, then hastily penned an article for the Nov. 14 issue of ZEITSCHRIFT FURE PHYSIK A.
"This is excellent work," says Albert Ghiorso, a physicist at Lawrence Berkeley Laboratory in Berkeley, Calif., who led the discoverers of element 106. "There's no question in my mind that they've actually found element 110."
In 1991, scientists in Berkeley, performing similar experiments, reported seeing evidence of element 110, but it was not confirmed. Meanwhile, in Dubna, Russia, researchers have experiments under way to produce an isotope of element 110 with a mass of 273 by bombarding plutonium with sulfur. Other experiments at GSI are pursuing more heavy isotopes.
"This is all very exciting," says Ghiorso. "Who knows, we may see more isotopes before the year's end. That would be magnificent."
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|Title Annotation:||heaviest known element has an atomic number of 110 and a mass of 270|
|Date:||Nov 26, 1994|
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