Flerovium (114Fl) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 289Fl in 1999 (or possibly 1998). Flerovium has six known isotopes, along with the unconfirmed 290Fl, and possibly two nuclear isomers. The longest-lived isotope is 289Fl with a half-life of 1.9 seconds, but 290Fl may have a longer half-life of 19 seconds.
List of isotopes
|-id=Flerovium-284 | rowspan=2|284Fl | rowspan=2 style="text-align:right" | 114 | rowspan=2 style="text-align:right" | 170 | rowspan=2|284.18119(70)# | rowspan=2 style="text-align:center" | 2015 | rowspan=2| | SF (76%) | (various) | rowspan=2|0+ |- | α (24%) | 280Cn |-id=Flerovium-285 | 285Fl | style="text-align:right" | 114 | style="text-align:right" | 171 | 285.18350(43)# | style="text-align:center" | 2010 | | α | 281Cn | 3/2+# |-id=Flerovium-286 | rowspan=2|286Fl | rowspan=2 style="text-align:right" | 114 | rowspan=2 style="text-align:right" | 172 | rowspan=2|286.18423(59)# | rowspan=2 style="text-align:center" | 2004 | rowspan=2| | α (55%) | 282Cn | rowspan=2|0+ |- | SF (45%) | (various) |-id=Flerovium-287 | rowspan=2| 287Fl | rowspan=2 style="text-align:right" | 114 | rowspan=2 style="text-align:right" | 173 | rowspan=2| 287.18672(66)# | rowspan=2 style="text-align:center" | 2004 | rowspan=2| | α | 283Cn | rowspan=2| |- | EC? | 287Nh |-id=Flerovium-288 | 288Fl | style="text-align:right" | 114 | style="text-align:right" | 174 | 288.18778(82)# | style="text-align:center" | 2004 | 653(113) ms | α | 284Cn | 0+ |-id=Flerovium-289 | 289Fl | style="text-align:right" | 114 | style="text-align:right" | 175 | 289.19052(55)# | style="text-align:center" | 2004 | [] | α | 285Cn | 5/2+# |-id=Flerovium-289m | style="text-indent:1em" | 289mFlDiscovery of this isomer is unconfirmed | colspan="3" style="text-indent:2em" | 750(280)# keV | style="text-align:center" | 2012 | | α | 285mCn | |-id=Flerovium-290 | rowspan=2 | 290FlDiscovery of this isotope is unconfirmed | rowspan=2 style="text-align:right" | 114 | rowspan=2 style="text-align:right" | 176 | rowspan=2 | 290.19188(75)# | rowspan=2 style="text-align:center" | (2016) | rowspan=2 | 19 s? | EC | 290Nh | rowspan=2 | 0+ |- | α | 286Cn
Isotopes and nuclear properties
Nucleosynthesis
Target-projectile combinations leading to Z=114 compound nuclei The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with an atomic number of 114.
Target Projectile CN Attempt result208Pb76Ge284Fl238U50Ti288Fl238U48Ti286Fl244Pu48Ca292Fl242Pu48Ca290Fl240Pu48Ca288Fl239Pu48Ca287Fl250Cm40Ar290Fl248Cm40Ar288Fl
Cold fusion This section deals with the synthesis of nuclei of flerovium by so-called "cold" fusion reactions. 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 excited nucleus then decays to the ground state via the emission of one or two neutrons only.
208Pb(76Ge,xn)284−xFl The first attempt to synthesise flerovium in cold fusion reactions was performed at Grand accélérateur national d'ions lourds (GANIL), France in 2003. No atoms were detected, providing a yield limit of 1.2 pb. The team at RIKEN have indicated plans to study this reaction.
Hot fusion This section deals with the synthesis of nuclei of flerovium by so-called "hot" fusion reactions. 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. The excited nucleus then decays to the ground state via the emission of 3–5 neutrons. Fusion reactions utilizing 48Ca nuclei usually produce compound nuclei with intermediate excitation energies (~30–35 MeV) and are sometimes referred to as "warm" fusion reactions. This leads, in part, to relatively high yields from these reactions.
248Cm(40Ar,xn)288-xFl One of the first attempts at synthesis of superheavy elements was performed by Albert Ghiorso et al. and Stan Thompson et al. in 1968 at the Lawrence Berkeley National Laboratory using this reaction. 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. This first unsuccessful synthesis attempt provided early indications of cross-section and half-life limits for superheavy nuclei producible in hot fusion reactions.
244Pu(48Ca,xn)292−xFl (x=2?,3,4,5) The first experiments on the synthesis of flerovium were performed by the team in Dubna in November 1998. They were able to detect a single, long decay chain, assigned to . The reaction was repeated in 1999 and a further two atoms of flerovium were detected. The products were assigned to . The team further studied the reaction in 2002. During the measurement of the 3n, 4n, and 5n neutron evaporation excitation functions they were able to detect three atoms of , twelve atoms of the new isotope , and one atom of the new isotope 287Fl. Based on these results, the first atom to be detected was tentatively reassigned to or 289mFl, whilst the two subsequent atoms were reassigned to and therefore belong to the unofficial discovery experiment. In an attempt to study the chemistry of copernicium as the isotope , this reaction was repeated in April 2007. Surprisingly, a PSI-FLNR directly detected two atoms of forming the basis for the first chemical studies of flerovium.
In June 2008, the experiment was repeated in order to further assess the chemistry of the element using the isotope. A single atom was detected seeming to confirm the noble-gas-like properties of the element.
During May–July 2009, the team at GSI studied this reaction for the first time, as a first step towards the synthesis of tennessine. The team were able to confirm the synthesis and decay data for and , producing nine atoms of the former isotope and four atoms of the latter.
242Pu(48Ca,xn)290−xFl (x=2,3,4,5) The team at Dubna first studied this reaction in March–April 1999 and detected two atoms of flerovium, assigned to 287Fl. The reaction was repeated in September 2003 in order to attempt to confirm the decay data for 287Fl and 283Cn since conflicting data for 283Cn had been collected (see copernicium). The Russian scientists were able to measure decay data for 288Fl, 287Fl and the new isotope 286Fl from the measurement of the 2n, 3n, and 4n excitation functions."Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions 233,238U, 242Pu, and248Cm+48Ca" , Oganessian et al., JINR preprints, 2004. Retrieved on 2008-03-03
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.
The team at Berkeley, using the Berkeley gas-filled separator (BGS), continued their studies using newly acquired targets by attempting the synthesis of flerovium in January 2009 using the above reaction. In September 2009, they reported that they had succeeded in detecting two atoms of flerovium, as and , confirming the decay properties reported at the FLNR, although the measured cross sections were slightly lower; however the statistics were of lower quality.
In April 2009, the collaboration of Paul Scherrer Institute (PSI) and Flerov Laboratory of Nuclear Reactions (FLNR) of JINR carried out another study of the chemistry of flerovium using this reaction. A single atom of 283Cn was detected.
In December 2010, the team at the LBNL announced the synthesis of a single atom of the new isotope 285Fl with the consequent observation of 5 new isotopes of daughter elements.
239,240Pu(48Ca,xn)287,288−xFl (x=3 for 239Pu; x=3, 4 for 240Pu) The FLNR had plans to study light isotopes of flerovium, formed in the reaction between 239Pu or 240Pu and 48Ca: in particular, the decay products of 283Fl and 284Fl were expected to fill in the gap between the isotopes of the lighter superheavy elements formed by cold fusion with 208Pb and 209Bi targets and those formed by hot fusion with 48Ca projectiles. These reactions were studied in 2015. 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. Three atoms of 285Fl were also produced. The Dubna team repeated their investigation of the 240Pu+48Ca reaction in 2017, observing three new consistent decay chains of 285Fl, an additional decay chain from this nuclide that may pass through some isomeric states in its daughters, a chain that could be assigned to 287Fl (likely stemming from 242Pu impurities in the target), and some spontaneous fission events of which some could be from 284Fl, though other interpretations including side reactions involving the evaporation of charged particles are also possible.
As a decay product Most of the isotopes of flerovium have also been observed in the decay chains of livermorium and oganesson.
Evaporation residueObserved Fl isotope294Lv ?? 290Fl ?293Lv289Flsee livermorium292Lv288Fl291Lv287Fl294Og, 290Lv286Flsee oganesson288Lv284Fl
Retracted isotopes
285Fl In the claimed synthesis of 293Og in 1999, the isotope 285Fl was identified as decaying by 11.35 MeV alpha emission with a half-life of 0.58 ms. The claim was retracted in 2001. This isotope was finally created in 2010 and its decay properties supported the fabrication of the previously published decay data.
Fission of compound nuclei with an atomic number of 114 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. The nuclear reaction used is 244Pu+48Ca. The results have revealed how nuclei such as this fission predominantly by expelling closed shell nuclei such as 132Sn (Z = 50, N = 82). It was also found that the yield for the fusion-fission pathway was similar between 48Ca and 58Fe projectiles, indicating a possible future use of 58Fe projectiles in superheavy element formation.see Flerov lab annual reports 2000–2006
Nuclear isomerism
289Fl 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. This activity was not observed in repetitions of the direct synthesis of this isotope. 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. All subsequent decays were very similar to that observed from 289Fl, presuming that the parent decay was missed. This strongly suggests that the activity should be assigned to an isomeric level. The absence of the activity in recent experiments indicates that the yield of the isomer is ~20% compared to the supposed ground state and that the observation in the first experiment was a fortunate (or not as the case history indicates). Further research is required to resolve these issues.