In 1967 G.N. Flerov reported that a Soviet team working at the Joint
Institute for Nuclear Research at Dubna may have
produced a few atoms of 260-105 and 261-105 by bombarding 243Am with
22Ne. The evidence was based on
time coincidence measurements of alpha energies.
In 1970 Dubna scientists synthesized Element 105 and, by the end of
April 1970, "had investigated all the types of decay of
the new element and had determined its chemical properties," according
to a report in 1970. The Soviet group had not
proposed a name for 105. In late April 1970, it was announced that
Ghiorso, Nurmia, Haris, K.A.Y. Eskola, and P.L.
Eskola, working at the University of California at Berkeley, had positively
identified element 105. The discovery was made by bombarding a target of
249Cf with a beam of 84 MeV nitrogen nuclei in the Heavy Ion Linear Accelerator
(HILAC). When a 15N nuclear is absorbed by a 249Cf nucleus, four neutrons
are emitted and a new atom of 260-105 with a half-life of 1.6 s is formed.
While the first atoms of Element 105 are said to have been detected conclusively
on March 5, 1970, there is evidence that Element 105 had been formed in
Berkeley experiments a year earlier by the method described.
Ghiorso and his associates have attempted to confirm Soviet findings
by more sophisticated methods without success. The
Berkeley Group proposed the name hahnium -- after the late German scientist
Otto Hahn (1879-1968) -- and symbol Ha.
However, the International Union of Pure and Applied Chemistry panel
members in 1977 recommended that element 105 be
named to Dubnium (symbol Db) after the site of the Joint Institute
for Nuclear Research in Russia. Unfortunately, the name
hahnium will not be used again according to the rules for naming new
elements. Some scientists still use the earlier name of
hahnium because it had been used for about 25 years.
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