Superheavies extend periodic table to 115
A team from the Joint
Institute for Nuclear Research (JINR) in Dubna, Russia,
and the Lawrence Livermore National Laboratory (LLNL) in
the US, has published results on the synthesis of two new
superheavy elements, element 113 and element 115. In
experiments conducted at the JINR U400 cyclotron with the
Dubna gas-filled separator, the team observed decay
chains that confirm the existence of the two elements,
with element 113 produced via the alpha decay of element
115 (Oganessian et al. 2004).
The experiments produced four atoms each of element 115
and element 113 through the fusion reaction of calcium-48
nuclei at an energy of 248 MeV with nuclei in a target of
amercium-243. The team observed three similar decay
chains, each consisting of five consecutive alpha decays
that together took less than 30 seconds and terminated in
the spontaneous fission of dubnium-268, an isotope of
element 105 (which was named after Dubna) with a half-life
of 16 hours. An interesting fourth decay chain ending in
dubnium-267 was also observed when the energy of the
incident calcium ions was slightly increased.
The discovery was made possible through the use of the
intense calcium-48 beam from JINR's U400 cyclotron.
"Twenty years ago no one would have ever thought
that this was possible because the technology to produce
such an element just wasn't there," explained Joshua
Patin, LLNL's primary data analyst on the team. "But
with the efficiency of the Russian cyclotron and the
ability to run the experiments for long periods of time,
we were able to achieve this tremendous accomplishment."
The americium target material was supplied by the LLNL.
Zdroj: CERN Courier
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