Flerovium

Flerovio is the name of a radioactive chemical element with the symbol Fl and atomic number 114. Named after Gueorgui Fliorov.

To date around 80 decays of flerovium atoms have been observed, 50 of them directly and 30 from the decay of the heavier elements livermorium and oganeson. All the decays have been assigned to the four neighboring isotopes with mass numbers 286-289. The longest-lived isotope currently known is ²⁸⁹Fl₁₁₄ with a half-life of approximately 2.6 s, although there is evidence of an isomer, ^{289b< /sup>Fl₁₁₄, with a half-life of about 66 s, which would be one of the longest-lived nuclei in the superheavy element region.}

Very recent chemical experiments have strongly indicated that element 114 does not possess 'eka'lead-like properties and seems to behave like the first superheavy element, exhibiting noble gas-like properties due to relativistic effects.

History

Element Discovery

In December 1998, scientists at the Dubna Joint Institute for Nuclear Research in Russia bombarded a Pu-244 target with Ca-48 ions. A single atom of element 114, assigned to the isotope ²⁸⁹Uuq₁₁₄, was produced and decayed by alpha emission of 9.67 MeV, with a half-life of 30 s. This observation was later published in January 1999. However, the observed decay chain 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, called, ^289mFl₁₁₄.

In March 1999, the same team replaced the Pu-244 target with a Pu-242 target in order to produce other isotopes. On this occasion, two atoms of element 114 were produced, which disintegrated by alpha emission of 10.29 MeV with a half-life of 5.5 s. They were assigned as ²⁸⁷Uuq₁₁₄. Again, this activity has not been observed again and it is not clear which core occurred. It is possible that it was a meta-stable isomer, called ^287mUuq₁₁₄.

The now confirmed discovery of element 114 was made in June 1999, when the Dubná team repeated the Pu-244 reaction. This time two atoms of element 114 were produced, which decayed by emission of alpha particles of 9.82 MeV, with a half-life of 2.6 s.

This activity was initially misassigned to ²⁸⁸Uuq₁₁₄, due to confusion regarding previous observations. New work in December 2002, allowed a positive reassignment to ²⁸⁹Fl₁₁₄,

²⁴⁴Pu₉₄ + ⁴⁸Ca₂₀ → ²⁹²Fl₁₁₄^♪ → ²⁸⁹Fl₁₁₄ +3 ¹n₀

In May 2009, the IUPAC Joint Working Party (JWP) published a report on the discovery of element 112 copernicium acknowledging the discovery of the isotope ²⁸³Cn₁₁₂ . This involves the de facto discovery of element 114, the recognition of the data for the synthesis of ²⁸⁷Uuq₁₁₄ and ²⁹¹Uuh₁₁₆ (see below), related to ²⁸³Cn₁₁₂, although this cannot be determined as the first element synthesis. An upcoming JWP report will discuss these issues.

The discovery of element 114, like ²⁸⁷Uuq₁₁₄ and ²⁸⁶Uuq₁₁₄, was confirmed in January 2009 at Berkeley. This was followed by the confirmation of ²⁸⁸Uuq₁₁₄ and ²⁸⁹Uuq₁₁₄ in July 2009 in the GSI (see section 2.1.3).

Names

Ununquadio (Uuq) is a temporary IUPAC systematic element name. Researchers often refer to the element simply as element 114.

According to IUPAC recommendations, the discoverer of a new element has the right to suggest a name. On December 8, 2011, it was named Flerovio in honor of Gueorgui Fliórov.

Current Experiments

In April 2009, the Paul Scherrer Institute (PSI) in collaboration with the Flyov Laboratory of Nuclear Reactions (FLNR) of the Joint Institute for Nuclear Research conducted another study of the chemistry of element 114. The results are not yet available.

Future Experiments

The RIKEN team has outlined plans to study the cold fusion reaction:

²⁰⁸Pb₈₂ + ⁷⁶Ge₃₂ → ²⁸⁴Fl₁₁₄^♪ →?

The Transactinide Separator and Chemistry Apparatus (TASCA) collaboration based at the Gesellschaft für Schwerionenforschung (GSI) will perform their first chemistry experiments on E114 starting in August 2009, after their successful production of the element in April 2009.

The FLNR has future plans to study light isotopes of element 114, formed in the reaction between ²³⁹Pu and ⁴⁸Ca.

Isotopes and nuclear properties

Nucleosynthesis

Projectile-target combinations leading to Z=114 composite nuclei

The table below contains various combinations of targets and projectiles that could be used to form composite nuclei with Z=114.

Destination	Proyectil	NC	Expected outcome
208Pb	76Ge	284114	Lack of data
232Th	54Cr	286114	Successful reaction
238U	50Ti	288114	Reaction not yet attempted
244Pu	48Ca	292114	Successful reaction
242Pu	48Ca	290114	Successful reaction
239Pu	48Ca	287114	Successful reaction
248Cm	40Ar	288114	Reaction not yet attempted
249Cf	36S	285114	Reaction not yet attempted

Cold Fusion

This section deals with the synthesis of flerovium nuclei by so-called "cold" fusion reactions. These are processes that create compound nuclei at low excitation energies (~10-20 MeV, hence the term "cold"), leading to a higher probability of fission survival. The excited nucleus then decays to the ground state through the emission of only one or two neutrons.

208Pb(76Ge, xn)284−x114

The first attempt to synthesize element 114 in cold fusion reactions was made at the Grand Accélérateur National d'Ions Lourds (GANIL) in France in 2003. No atoms have been detected establishing a detection limit of 1.2 bp.

Hot Fusion

This section deals with the synthesis of flerovium nuclei by so-called "hot" fusion reactions. These are processes that create compound nuclei at high excitation energies (~40-50 MeV, hence the term 'hot'), leading to a lower probability of fission survival. The excited nucleus then falls to the ground state through the emission of 3-5 neutrons. Fusion reactions using ⁴⁸Ca nuclei usually produce compound nuclei with intermediate excitation energies (~30-35 MeV) and are sometimes called "warm" fusion reactions. This leads, in part, to relatively high yields for these reactions.

244Pu(48Ca, xn)292−x114 (x=3,4,5)

The first experiment to synthesize element 114 was carried out by the team in Dubná in November 1998. They were able to detect a single, long decay chain, assigned to ²⁸⁹114. The reaction was repeated in 1999 and another 2 atoms of element 114 were detected. The products were assigned to ²⁸⁸114. The team also studied the reaction in 2002. During the measurement of the evaporation excitation functions of 3n, 4n and 5n were able to detect 3 atoms of ²⁸⁹Uuq₁₁₄, 12 atoms of the new isotope ²⁸⁸Uuq₁₁₄, and 1 atom of the new isotope ²⁸⁷Uuq₁₁₄. Based on these results, the first atom to be detected was provisionally assigned to ²⁹⁰Uuq₁₁₄ or ^289mUuq₁₁₄., while the two subsequent atoms were assigned to ²⁸⁹Uuq₁₁₄ and therefore belong to unofficial experimental discovery. In an attempt to study the chemistry of element 112 as the isotope ²⁸⁵Cn₁₁₂, this reaction was repeated in April 2007. Surprisingly, the PSI-FLNR directly detected 2 atoms of ²⁸⁸Uuq< sub>114 which form the basis for the first chemical studies of element 114.
In June 2008, the experiment was repeated in order to better assess the chemistry of the element using the isotope ²⁸⁹Uuq₁₁₄. The single atom that was detected seems to confirm the noble gas properties of the element.
In May-July 2009, the GSI team studied this reaction, for the first time, as a first step towards the synthesis of element 117. The team was able to confirm the synthesis and decay data for ^{288< /sup>Uuq₁₁₄ and 289Uuq₁₁₄.}

242Pu(48Ca, xn)290−x114 (x=2,3,4)

Dubná's team first studied this reaction in March-April 1999 and detected two atoms of element 114, assigned to ²⁸⁷Uuq₁₁₄. The reaction was repeated in September 2003 to try to confirm the data on the disintegrations of ²⁸⁷Uuq₁₁₄ and ²⁸³Cn_{112 as they conflicted with data from ²⁸³Cn112 that had already been collected (see copernicius). Russian scientists were able to measure data from the decay of ²⁸⁸Uuq114, ²⁸⁷Uuq114 and the new isotope ²⁸⁶Uuq114 from the measurements for the excitation functions of 2n, 3n and 4n.
In April 2006, a PSI-FLNR collaboration used the reaction to determine the first chemical properties of element 112 by producing ²⁸³Cn112 as a waste product. In a confirmatory experiment in April 2007, the team was able to detect ²⁸⁷Uuq114 directly and thus measure some initial data on the atomic chemical properties of element 114..
The Berkeley team, using the Berkeley gas-filled separator (BGS), continued their studies using the recently acquired ²⁴²Pu targets to attempt the synthesis of element 114 in January 2009 using the above reaction. In September 2009, they reported that they had succeeded in detecting 2 E114 atoms, as ²⁸⁷Uuq114 and ²⁸⁶Uuq114, confirming the decay properties reported in the FLNR, although the measured cross sections were slightly lower, but the statistics were of lower quality.}

Like a decay product

Isotopes of flerovium have also been observed in the decay of elements 116 and 118 (see Oganeson for the decay chain).

Retired Isotopes

285Uuq114

In the claimed synthesis of ²⁹³Uuo₁₁₈ in 1999, the isotope ²⁸⁵Uuq₁₁₄ was identified as alpha emission decay of 11.35 MeV with a half-life of 0.58 ms. The claim was withdrawn in 2001 and hence this flerovium isotope is currently unknown or unconfirmed.

Timeline of isotope discovery

Fission of compound nuclei with Z=114

Between 2000-2004 several experiments have been carried out at the Fliórov Laboratory of Nuclear Reactions in Dubná to study the fission characteristics of the compound nucleus ²⁹²Uuq₁₁₄. The nuclear reaction used is ²⁴⁴Pu + ⁴⁸Ca. The results have revealed how nuclei like this fission predominantly ejecting closed-shell nuclei like ¹³²Sn₅₀. Performance for the fusion-fission pathway was also found to be similar between ⁴⁸Ca and ⁵⁸Fe projectiles, indicating a possible future use of ^{58< projectiles. /sup>Faith in the formation of superheavy elements.}

Nuclear isomerism

289Uuq114

In the first alleged synthesis of element 114, an isotope assigned as ²⁸⁹Uuq₁₁₄ decayed emitting a 9.71 MeV alpha particle, with a duration of 30 seconds. This activity has not been observed in replicates of the direct synthesis of this isotope. However, in a single instance of the synthesis of ²⁹³ Uuh₁₁₆, a decay chain was measured starting with the emission of a 9.63 MeV alpha particle, with a half-life of 2.7 minutes. All subsequent decompositions were very similar to those observed from ²⁸⁹Uuq₁₁₄, assuming that the parental decomposition was lost. This strongly suggests that the activity must be assigned to an isomeric level. The absence of activity in recent experiments indicates that the isomer yield is ~20% relative to the ground state and assumes that the observation in the first experiment was fortunate (or not as indicated by the case history). Additional research is required to resolve these issues.

287Uuq114

Similar to ²⁸⁹Uuq₁₁₄, early experiments with a ²⁴²Pu target identified an isotope ²⁸⁷ Uuq₁₁₄ that decayed by emission of a 10.29 MeV alpha particle, with a lifetime of 5.5 seconds. The daughter nucleus spontaneously fissioned with a lifetime in agreement with the previous synthesis of ²⁸³Cn₁₁₂. Both of these activities have not been observed (see copernicio). However, the correlation suggests that the results are not random and are possible due to the formation of isomers whose performance is obviously dependent on production methods. Additional research is required to unravel these discrepancies.

Isotope Yields

The following tables provide the cross sections and excitation energies for fusion reactions that directly produce flerovium isotopes. Data in bold represent maxima from excitation function measurements.

Cold Fusion

Hot Fusion

Theoretical calculations

Waste evaporation cross sections

The following table contains various target-projectile combinations for which calculations have provided estimates for the cross-sectional yields of different channels of neutron evaporation. The channel with the highest expected performance is indicated.

MD = multi-dimensional; DNS = Dinuclear System; σ = cross section

Features of Disintegration

Theoretical estimate of the alpha decay half-life of element 114 isotopes supports the experimental data. The fission survival of the isotope ²⁹⁸Uuq₁₁₄ is predicted for alpha decay with a half-life of about 17 days.

In search of the island of stability: 298Uuq114

According to macroscopic-microscopic (MM) theory, Z = 114 is the next spherical magic number. This means that these nuclei are spherical in their ground state and must have high and wide fission barriers to deformation and therefore long half-lifes for simple partial fission.

In the region of Z = 114, MM theory indicates that N = 184 is the next magic number of spherical neutrons and puts the nucleus ²⁹⁸Uuq₁₁₄ as a strong candidate for the next doubly magical spherical nucleus, after ²⁰⁸Pb₈₂ (Z = 82, N = 126). ²⁹⁸Uuq₁₁₄ appears to be at the center of a hypothetical 'island of stability'. However, other relativistic mean field (RMF) theory calculations propose Z = 120, 122, and 126 as alternative proton magic numbers, depending on the selected parameter set. It is possible that instead of a peak for a specific proton shell, there is a plateau of proton shell effects from Z = 114 to Z = 126.

It should be noted that calculations suggest that the minimum shell correction energy and hence the highest fission barrier exists for ²⁹⁷115, caused by pair effects. Due to the high fission barriers expected, any nucleus within this island of stability will exclusively decay by alpha particle emission and as such the nucleus with the longest predicted half-life is ²⁹⁸Uuq> ₁₁₄. The expected half-life is unlikely to reach values greater than 10 minutes unless the N=184 neutron shell proves to be more stabilizing than predicted, for which some evidence exists. In addition, ²⁹⁷Uuq₁₁₄ may have an even longer half-life due to the odd neutron effect, which creates transitions between similar Nilsson levels with Q _{values. alpha} minors.

In either case, an island of stability does not represent nuclei with the longest half-lives, but rather those that are significantly stabilized against fission by closed-shell effects.

Evidence for a closed proton shell for Z = 114

While the evidence for closed neutron shells can be taken directly from the systematic variation of Q_alpha values for ground-state transitions has been fundamental, the evidence for proton shells closed come from the half-life of spontaneous (partial) fission. These data can sometimes be difficult to extract, due to low production rates and weak single fission (SF) branching. In the case of Z = 114, evidence for the effects of this proposed closed shell comes from the comparison between pairs of ²⁸²Cn₁₁₂ nuclei (T_SF 1/2 = 0.8 ms) and ²⁸⁶Uuq₁₁₄ (T_SF1/2 = 130 ms), and on the other side ²⁸⁴Cn₁₁₂ (T_SF = 97 ms) and ²⁸⁸Uuq₁₁₄ (T_SF >800ms). Other evidence that comes from measuring the partial SF half-life of nuclei with Z> 114, such as ²⁹⁰Uuh₁₁₆ and ²⁹²Uuo₁₁₈ (both isotones, with N = 174). The extraction of effects of Z = 114 is complicated by the presence of a dominant effect N = 184 in this region.

Difficulty of the synthesis of 298Uuq114

Direct synthesis of the nucleus of ²⁹⁸Uuq₁₁₄ by an evaporation-fusion pathway is impossible, as no known combination of target and projectile can provide 184 neutrons in the compound nucleus.

It has been suggested that a neutron-rich isotope formed by quasifission (partial melting followed by fission) of a massive nucleus. Such nuclei tend to fission with the formation of close-shell isotopes Z = 20 / N = 20 (⁴⁰Ca), Z = 50 / N = 82 (^{132< /sup>Sn) or Z = 82 / N = 126 (208Pb / 209Bi). If Z = 114 represents a closed shell, then the following hypothetical reaction may represent a synthetic method:}

²⁰⁴Hg₈₀ + ¹³⁶Xe₅₄ → ²⁹⁸Uuq₁₁₄ + ⁴⁰Ca₂₀ + 2 ¹n₀

It has recently been shown that multi-nucleon transfer reactions in actinide nuclei collisions (such as U + Cm) could be used to synthesize neutron-rich superheavy nuclei located on the island of stability.

It is also possible that ²⁹⁸Uuq₁₁₄ could be synthesized by the alpha decay of a massive nucleus. This method will largely depend on the SF stability of such nuclei, since the half-life for alpha decay is expected to be very short. The yields of these reactions are also very likely to be extremely small. Such a reaction is:

²²⁴Pu₉₄(⁹⁶Zr₄₀, 2n) → ³³⁸Utq₁₃₄ → → ²⁹⁸Uuq₁₁₄ + 10 ⁴He₂

Chemical properties

Extrapolated chemical properties

Oxidation States

Element 114 is predicted to be the second member of the 7p series of nonmetals and the heaviest member of group 14 (IVA) in the Periodic Table, below lead. Each of the members of this group shows the group oxidation state of +IV and the later members of this group have increased +II chemistry due to the appearance of the inert pair effect. Tin represents the point where the stability of the +II and +IV states is similar. Lead, the heaviest member, represents a change from the +IV state to the +II state. Element 114, therefore, follows this trend and has an oxidizing state + IV, and a stable state + II.

Chemistry

Element 114 should have the chemical properties of eka-lead and thus could form a monoxide, UuqO, and dihalides, UuqF₂, UuqCl₂, UuqBr ₂, and UuqI₂. If the +IV + state is accessible, it is likely only possible in the oxide, UuqO₂, and the fluoride, UuqF₄. It can also show a mixture of oxides, Uuq₃O₄ analogous to Pb₃O₄.

Some studies also suggest that the chemical behavior of element 114 may, in fact, be closer to that of the noble gas radon than lead.

Experimental Chemistry

Atomic Gas Phase

Two experiments were performed in May-April 2007 in an FLNR-PSI collaboration to study the chemistry of element 112. The first experiment involved the reaction:

²⁴²Pu⁴⁸Ca.3n) → ²⁸⁷Uuq₁₁₄ and the second implied the reaction:

²⁴⁴Pu⁴⁸Ca,4n) → ²⁸⁸Uuq₁₁₄.

The adsorption properties of the resulting atoms on a gold surface were compared with those of radon. The first experiment allowed the detection of 3 atoms of ²⁸³Cn₁₁₂ (see copernicium), but also apparently detected 1 atom of ²⁸⁷Uuq< sub>114. This result was a surprise, given that the transport time of the product atoms is ~2 s, so the element 114 atoms could decay before absorption. In the second reaction, 2 atoms of ²⁸⁸Uuq₁₁₄ and possibly 1 atom of ²⁸⁹Uuq₁₁₄ were detected. >. Two of the three atoms displayed adsorption characteristics associated with a volatile element, which has been suggested to be of the noble gas type, but not predicted by more recent calculations. These experiments did, however, provide independent confirmation for the discovery of elements 112, 114, and 116, through comparison with published decay data. Further experiments were performed in 2008 to confirm this important result and a single ²⁸⁹Uuq₁₁₄ atom was detected giving data consistent with previous data in support of the interaction as a noble gas of element 114 with gold.