Isotopes of flerovium
These are processes which create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of survival from fission.
The first attempt to synthesise flerovium in cold fusion reactions was performed at Grand accélérateur national d'ions lourds (GANIL), France in 2003.
These are processes which create compound nuclei at high excitation energy (~40–50 MeV, hence "hot"), leading to a reduced probability of survival from fission.
No events attributable to superheavy nuclei were identified; this was expected as the compound nucleus 288Fl (with N = 174) falls ten neutrons short of the closed shell predicted at N = 184.
[13] This first unsuccessful synthesis attempt provided early indications of cross-section and half-life limits for superheavy nuclei producible in hot fusion reactions.
[20][21] In April 2006, a PSI-FLNR collaboration used the reaction to determine the first chemical properties of copernicium by producing 283Cn as an overshoot product.
In a confirmatory experiment in April 2007, the team were able to detect 287Fl directly and therefore measure some initial data on the atomic chemical properties of flerovium.
One new isotope was found in both the 240Pu(48Ca,4n) and 239Pu(48Ca,3n) reactions, the rapidly spontaneously fissioning 284Fl, giving a clear demarcation of the neutron-poor edge of the island of stability.
Several experiments have been performed between 2000 and 2004 at the Flerov Laboratory of Nuclear Reactions in Dubna studying the fission characteristics of the compound nucleus 292Fl.
[28] In the first claimed synthesis of flerovium, an isotope assigned as 289Fl decayed by emitting a 9.71 MeV alpha particle with a lifetime of 30 seconds.
However, in a single case from the synthesis of 293Lv, a decay chain was measured starting with the emission of a 9.63 MeV alpha particle with a lifetime of 2.7 minutes.
This assignment necessitates the postulation of undetected electron capture to 290Nh, because it would otherwise be difficult to explain the long half-lives of the daughters of 290Fl to spontaneous fission if they are all even-even.
This would suggest that the erstwhile isomeric 289mFl, 285mCn, 281mDs, and 277mHs are thus actually 290Nh (electron capture of 290Fl having been missed, as current detectors are not sensitive to this decay mode), 286Rg, 282Mt, and the spontaneously fissioning 278Bh, creating some of the most neutron-rich superheavy isotopes known to date: this fits well with the systematic trend of increasing half-life as neutrons are added to superheavy nuclei towards the beta-stability line, which this chain would then terminate very close to.
[6] In a manner similar to those for 289Fl, first experiments with a 242Pu target identified an isotope 287Fl decaying by emission of a 10.29 MeV alpha particle with a lifetime of 5.5 seconds.
However, the correlation suggests that the results are not random and are possible due to the formation of isomers whose yield is obviously dependent on production methods.
The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels.
MD = multi-dimensional; DNS = Dinuclear system; σ = cross section Theoretical estimation of the alpha decay half-lives of the isotopes of the flerovium supports the experimental data.
However, other calculations using relativistic mean field (RMF) theory propose Z = 120, 122, and 126 as alternative proton magic numbers, depending upon the chosen set of parameters, and some entirely omit Z = 114 or N = 184.
The direct synthesis of the nucleus 298Fl by a fusion-evaporation pathway is impossible with current technology, as no combination of available projectiles and targets may be used to populate nuclei with enough neutrons to be within the island of stability, and radioactive beams (such as 44S) cannot be produced with sufficient intensities to make an experiment feasible.
