Darmstadt gets credit for new elements
The discovery of element
111 has been officially credited to the GSI laboratory in
Darmstadt, Germany, by a joint working party set up by
the International Union of Pure and Applied Chemistry (IUPAC)
and the sister union for physics (IUPAP). IUPAC has also
officially approved a proposal from GSI that element 110
- which was also discovered at the German lab - should be
known as darmstadtium (Ds).
Sigurd Hofmann and co-workers first created element 111
in December 1994 by colliding a beam of nickel-64 nuclei
with a target made of bismuth-209. The GSI team observed
three chains of events that signalled the production and
decay of nuclei that contained 111 protons and 161
However IUPAC - the organization that is responsible for
assessing such claims - was reluctant to accept this
result as conclusive proof for the discovery of a new
element because two of the decay chains involved isotopes
that were unknown at the time: meitnerium-268, which
contains 109 protons, and bohrium-264 (107 protons). The
next members of the chain - dubnium-206 (105 protons) and
lawrencium-256 (103 protons) - were known but the group
was unable to unambiguously measure their decay.
In 2000, the GSI team repeated their experiment with an
improved set-up and observed another three decay chains.
Moreover, this time Hofmann and co-workers succeeded in
detecting isotopes all the way down to lawrencium-256 and
the IUPAC-IUPAP working party accepted the new result (P
Karol et al. 2003 Pure Appl. Chem. 75 1601).
"IUPAC will now ask us to suggest a name for element
111 and we are in the process of discussing this at GSI,"
Hofmann told PhysicsWeb.
However, the working party reported that further results
will be needed before credit can be assigned for the
discovery of elements 112, 114 and 116. Evidence for
these new elements has been seen at GSI and in
experiments by Yuri Oganessian's group at the Dubna
Laboratory of Heavy Ion Nuclear Reactions in Russia.
Claims by a US team to have created element 118 in 1999
were subsequently retracted after it emerged that the
results had been fabricated by one member of the team.
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