for National Geographic News
A team of Russian and American physicists says it has created three atoms of a new element.
The as-yet-unnamed element, element 118, is the heaviest yet discovered, with a nucleus consisting of 118 protons and 176 neutrons.
The heaviest naturally occurring element is uranium, which has 92 protons. Its most common form, or isotope, has 146 neutrons. Scientists have also artificially created most of the other elements between uranium and element 118. (Related: "Nuclear Tech Not a 'New Capability' for North Korea, Experts Say" [October 13, 2006.)
The newest element was created in a particle accelerator in Dubna, Russia, that shot a beam of calcium-48 ions (containing 20 protons) into a target of californium 249, an artificial element with 98 protons (map of Russia).
To create a mere three atoms of element 118, the scientists spent two months bombarding the californium target with 30 billion billion calcium ions.
"Most of them just go right through the target and don't do anything," said Mark Stoyer, a nuclear chemist at Lawrence Livermore National Laboratory who was part of the research team.
Only rare head-on collisions occurring with just the right energy caused the two elements to stick together to form a new super-heavy atom, Stoyer said. "One of the reasons we did it in Dubna is because they have a very intense beam of calcium 48."
A detector allowed the researchers to track radiation and by-products created by the high-energy collisions.
By working backward through a decay sequence, the scientists are reasonably certain they created element 118, even though the highly unstable new atoms survived only a millisecond apiece.
Element 118 first decayed into element 116, then into element 114. That decayed into element 112, which split into two roughly equal pieces, the researchers say.
Their next goal is to create element 120 by beaming iron atoms (26 protons) at a plutonium target (which has 94 protons).
No Sure Thing
SOURCES AND RELATED WEB SITES