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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