Saturday, September 26, 2009

Researchers at Lawrence Berkeley National Laboratory, California have confirmed the existence of the superheavy element 114 — otherwise known as ununquadium — ten years after its first observation by Russian scientists. Containing 114 protons, this is the heaviest element detected in multiple laboratories and another step towards the theorised island of stability, the "holy grail" of such research.

The elusive element was first detected in 1998 at the Joint Institute for Nuclear Research, Dubna, Russia, when a plutonium target was bombarded with calcium ions accelerated in a cyclotron. Until now no other groups had been able to confirm the Russian team's results. "It’s unusual for important results like the Dubna group’s claim to have produced 114 to go unconfirmed for so long," said Ken Gregorich, part of the Berkeley team.

Nuclear reactions producing the element occur only rarely, and once produced it decays quickly. The Berkeley experiment was run for eight days almost continuously and only two nuclei of element 114 were detected during this time. Each was a different isotope, both with 114 protons but one with 172 neutrons and one with 173. The team had to use sophisticated gas-filled separators to find these among the many other products of the collisions. To make sure their analysis of the data was correct, it was run through two independent computer programs written by different members of the team.

Both isotopes of 114 observed decayed to element 112 in less than a second. The superheavy elements are typically short-lived, but theorists predict a so-called "island of stability", a group of elements that are much more stable because they contain "magic numbers" of protons and neutrons. According to Gregorich: "Based on the ideas of the 1960s, we thought when we got to element 114 we would have reached the Island of Stability". But more recent theories suggest that heavier elements may be needed. "The work we're doing now will help us decide which theories are correct and how we should modify our models," Gregorich continued.

The Berkeley group's results have been reported in the journal Physical Review Letters.





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