On 16 August 2003, at the 42nd IUPAC General Assembly in Ottawa,
Canada, the IUPAC Council officially approved the name for element
of atomic number 110, to be known as darmstadtium, with symbol
Ds. > View Press Release
The Questions and Answers below have been compiled from recent
communications with Dr. Sigurd Hofmann from the Gesellschaft
für Schwerionenforschung mbH (GSI) in Darmstadt, Germany, the
laboratory where Ds has been discovered.
Q. The element was produced in 1995. Why did the naming
take eight years? What was the name of the element in the interim
period?
A. The relatively long period before a name for element
110 was officially accepted was not based on uncertainties or major
objections from other laboratories. However, some clarification
was needed concerning experimental work made in Dubna and Berkeley
on element 110.
An IUPAC Technical Report on this subject was published by Karol
et al. (the Joint Working Party, JWP) in Pure
Appl. Chem.,
Vol 73, pp. 959-967, 2001. In that paper it was clearly stated
that "Element 110 has been discovered by this (Hofmann et al.,
Z. Phys. A350, 277-280, 1995) collaboration. All other work
was considered as insufficient to fulfill the criteria for the discovery
of a new element.
After this report, IUPAC set November 2002 as a deadline for suggesting
a name, which then, according to the rules, had to be made public
for a period of five months.
Interim names for elements to be discovered are recommended by
IUPAC.
For element 110 it was ununnilium, Uun.
However, in the laboratory jargon we simply used hundred ten, 110.
The first nucleus of 269Ds was produced on Nov. 9, 1994.
The publication was received by the editor on Nov. 14, 1994 and
the paper appeared early 1995.
Q.
How many of these nuclei have been produced to date?
A. By now a total of 48 nuclei of darmstadtium were measured
at different laboratories. The nuclei were attributed to 6 different
isotopes produced in different reactions. Some of the published
data is subject to further investigation and confirmation.
62Ni + 208Pb --> 269Ds + 1
n, 1994, GSI Darmstadt, 3 atoms
64Ni + 208Pb --> 271Ds + 1
n, 1994, GSI Darmstadt, 9 atoms
64Ni + 208Pb --> 271Ds + 1
n, 2000, GSI Darmstadt, 4 atoms
64Ni + 208Pb --> 271Ds + 1
n, 2000, LBNL Berkeley, 2 atoms
64Ni + 208Pb --> 271Ds + 1
n, 2002, RIKEN Japan, 14 atoms
64Ni + 207Pb --> 270Ds + 1
n, 2000, GSI Darmstadt, 8 atoms
70Zn + 208Pb --> 277Uub + 1
n, --> 273Ds + 1 alpha, 1996, GSI Darmstadt, 1 atom
70Zn + 208Pb --> 277Uub + 1
n, --> 273Ds + 1 alpha, 2000, GSI Darmstadt, 1 atom
48Ca + 244Pu --> 289Uuq + 3
n, --> 281Ds + 2 alpha, 1998, FLNR Dubna, 1 atom
48Ca + 244Pu --> 288Uuq + 4
n, --> 280Ds + 2 alpha, 1999, FLNR Dubna, 2 atoms
48Ca + 248Cm --> 292Uuh + 4
n, --> 280Ds + 3 alpha, 2000, FLNR Dubna, 1 atom
48Ca + 248Cm --> 292Uuh + 4
n, --> 280Ds + 3 alpha, 2001, FLNR Dubna, 2 atoms
The half-lives range from 180 microseconds for 269Ds
to 1.1 minute for 281Ds.
Q. Is there a scientific need to produce more of these
nuclei? In what way, does this specific achievement help to produce
other superheavy elements?
A. In order to better understand the synthesis of heavy
elements, it is necessary to produce them in different reactions
and at different beam energies, resulting in the so-called 'excitation
functions' which are the yield as function of the beam energy. In
these experiments one also increases the number of produced atoms.
A greater number of decays also exhibits more detailed information
on nuclear structure, e.g. nuclear deformation, angular momentum,
excited levels, decay modes like alpha or beta decay, or spontaneous
fission.
It also increases the statistical accuracy of half-life and decay
energy.
Q. Can you provide some story or episode of human interest
associated with the production of the element?
A. Here I would like to refer to my book:
Hofmann, S., On Beyond Uranium - Journey to the end of the Periodic
Table, Science Spectra Book Series, Volume 2, V. Moses, Series
Editor, ISBN 0-415-28495-3 (hardback)
Taylor and Francis, London and New York, 2002, pp. 216
> link
to publisher website or
> visit Taylor
& Francis eBookstore ... from here visitors are able to
use eSubscribe and ePrint/eCopy to access the sections of the book.
Q. What is the future plan in this expensive area of
research?
A. In order to achieve a more detailed exploration of the
structure and boundaries of the island of superheavy nuclei, technical
improvements have to be performed. The aim is to get increased beam
intensity, at least by a factor of 10, and to develop targets which
can stand these high intensities.
The most urgent physical question to be solved is, where actually
are the closed shells for the protons and neutrons located. Theory
presently predicts 114, 120 or 126 for the protons and 172 or 184
for the neutrons as possible candidates.
Of great importance is also the question regarding the strength
of these shells. Does only one major shell with strong shell effect
for the protons and neutrons exist, or is the shell strength more
equally distributed across a number of subshells?
These properties finally determine the production yield and the
lifetime of superheavy nuclei. Both decide the possibilities for
application of further techniques, like chemical separation to study
the chemical properties or capture of the atoms in ion traps to
perform high resolution mass spectroscopy and laser excitation of
the atomic electron shells.
What is your question?
E-mail Sigurd Hofmann or/and
visit <www.darmstadtium.com>
>
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