De facto discovery
In December 1998, scientists at Dubna (
Joint Institute for Nuclear Research) in Russia bombarded a Pu-244 target with Ca-48 ions. A single atom of element 114, decaying by 9.67 MeV alpha-emission with a lifetime of 30 s, was produced and assigned to 289114. This observation was subsequently published in January 1999.
[3] However, the decay chain observed has not been repeated and the exact identity of this activity is unknown, although it is possible that it is due to a meta-stable isomer, namely 289m114.
In March 1999, the same team replaced the Pu-244 target with a Pu-242 one in order to produce other isotopes. This time two atoms of element 114 were produced, decaying by 10.29 MeV alpha-emission with a half-life of 5.5 s. They were assigned as 287114.
[4] Once again, this activity has not been seen again and it is unclear what nucleus was produced. It is possible that it was a meta-stable isomer, namely 287m114.
The now-confirmed discovery of element 114 was made in June 1999 when the Dubna team repeated the Pu-244 reaction. This time, two atoms of element 114 were produced decaying by emission of 9.82 MeV alpha particles with a half life of 2.6 s.
[5]
This activity was initially assigned to 288114 in error, due to the confusion regarding the above observations. Further work in Dec 2002 has allowed a positive reassignment to 289114.
[6]
24494
Pu +
4820
Ca →
292114
Uuq* →
289114
Uuq + 3
10
n In May 2009, the Joint Working Party (JWP) of
IUPAC published a report on the discovery of element 112
ununbium in which they acknowledged the discovery of the isotope 283112.
[7] This therefore implies the
de facto discovery of element 114, from the acknowledgment of the data for the synthesis of 287114 and 291116 (see below), relating to 283112, although this may not be determined as the first synthesis of the element. An impending report by the JWP will discuss these issues.
The discovery of element 114, as 287114 and 286114, was confirmed in January 2009 at Berkeley. This was followed by confirmation of 288114 and 289114 in July 2009 at the GSI (see section 2.1.3).
http://en.wikipedia.org/wiki/Ununquadium