Isotopes of flerovium

Flerovium (Fl) is a synthetic element, and thus a standard atomic mass 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, and possibly 2 nuclear isomers. The longest-lived isotope is ²⁸⁹Fl with a half-life of 2.6 seconds.

Table

1. ↑ Abbreviations:
   SF: Spontaneous fission
2. ↑ Not directly synthesized, produced in decay chain of ²⁹⁴Og
3. ↑ Heaviest nuclide known to undergo spontaneous fission
4. 1 2 Existence of this isomer is uncertain

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.
• It is theorized that ²⁹⁸Fl will have a relatively long half-life.

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.

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.

²⁴⁴Pu(⁴⁸Ca,xn)^292−xFl (x=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 289
Fl.^[2] The reaction was repeated in 1999 and a further two atoms of flerovium were detected. The products were assigned to 288
Fl.^[3] 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 289
Fl, twelve atoms of the new isotope 288
Fl, and one atom of the new isotope²⁸⁷Fl. Based on these results, the first atom to be detected was tentatively reassigned to 290
Fl or ^289mFl, whilst the two subsequent atoms were reassigned to 289
Fl and therefore belong to the unofficial discovery experiment.^[4] In an attempt to study the chemistry of copernicium as the isotope 285
Cn, this reaction was repeated in April 2007. Surprisingly, a PSI-FLNR directly detected two atoms of 288
Fl 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 289
Fl 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 288
Fl and 289
Fl, producing nine atoms of the former isotope and four atoms of the latter.^[5]

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.^[6] 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. ^[7][8]

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 242
Pu 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 287
Fl and 286
Fl, confirming the decay properties reported at the FLNR, although the measured cross sections were slightly lower; however the statistics were of lower quality.^[9]

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.

²³⁹Pu(⁴⁸Ca,xn)^287−xFl

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

As a decay product

The isotopes of flerovium have also been observed in the decay chains of livermorium and oganesson.

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.

Chronology of isotope discovery

Fission of compound nuclei with an atomic number of 114

Several experiments have been performed between 2000–2004 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 between⁴⁸Ca and ⁵⁸Fe projectiles, indicating a possible future use of ⁵⁸Fe projectiles in superheavy element formation.^[12]

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.

²⁸⁷Fl

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. The daughter spontaneously fissioned with a lifetime in accord with the previous synthesis of²⁸³Cn. Both these activities have not been observed since (see copernicium). 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. Further research is required to unravel these discrepancies.

Yields of isotopes

The tables below provide cross-sections and excitation energies for fusion reactions producing flerovium isotopes directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.

Cold fusion

Hot fusion

Theoretical calculations

Evaporation residue cross sections

The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

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

Decay characteristics

Theoretical estimation of the alpha decay half-lives of the isotopes of the flerovium supports the experimental data.^[16][17] The fission-survived isotope ²⁹⁸Fl is predicted to have alpha decay half-life around 17 days.^[18][19]

In search for the island of stability: ²⁹⁸Fl

According to macroscopic-microscopic (MM) theory, Z=114 is the next spherical magic number. This means that such nuclei are spherical in their ground state and should have high, wide fission barriers to deformation and hence long SF partial half-lives.

In the region of Z=114, MM theory indicates that N=184 is the next spherical neutron magic number and puts forward the nucleus ²⁹⁸Fl as a strong candidate for the next spherical doubly magic nucleus, after ²⁰⁸Pb (Z=82, N=126). ²⁹⁸Fl is taken to be at the centre of a hypothetical "island of stability". 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. It is possible that rather than a peak at a specific proton shell, there exists a plateau of proton shell effects from Z=114–126.

It should be noted that calculations suggest that the minimum of the shell-correction energy and hence the highest fission barrier exists for ²⁹⁷Mc, caused by pairing effects. Due to the expected high fission barriers, any nucleus within this island of stability will exclusively decay by alpha-particle emission and as such the nucleus with the longest half-life is predicted to be ²⁹⁸Fl. The expected half-life is unlikely to reach values higher than about 10 minutes, unless the N=184 neutron shell proves to be more stabilising than predicted, for which there exists some evidence. In addition, ²⁹⁷Fl may have an even-longer half-life due to the effect of the odd neutron, creating transitions between similar Nilsson levels with lower Q_alpha values.

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

Evidence for Z=114 closed proton shell

While evidence for closed neutron shells can be deemed directly from the systematic variation of Q_alpha values for ground-state to ground-state transitions, evidence for closed proton shells comes from (partial) spontaneous fission half-lives. Such data can sometimes be difficult to extract due to low production rates and weak SF branching. In the case of Z=114, evidence for the effect of this proposed closed shell comes from the comparison between the nuclei pairings ²⁸²Cn (T_SF1/2 = 0.8 ms) and ²⁸⁶Fl (T_SF1/2 = 130 ms), and ²⁸⁴Cn (T_SF = 97 ms) and ²⁸⁸Fl (T_SF >800 ms). Further evidence would come from the measurement of partial SF half-lives of nuclei with Z>114, such as ²⁹⁰Lv and ²⁹²Og (both N=174 isotones). The extraction of Z=114 effects is complicated by the presence of a dominating N=184 effect in this region.

Difficulty of synthesis of ²⁹⁸Fl

The direct synthesis of the nucleus ²⁹⁸Fl by a fusion-evaporation pathway is impossible since no known combination of target and projectile can provide 184 neutrons in the compound nucleus.

It has been suggested that such a neutron-rich isotope can be formed by the quasifission (partial fusion followed by fission) of a massive nucleus. Such nuclei tend to fission with the formation of isotopes close to the closed shells Z=20/N=20 (⁴⁰Ca), Z=50/N=82 (¹³²Sn) or Z=82/N=126 (²⁰⁸Pb/²⁰⁹Bi). If Z=114 does represent a closed shell, then the hypothetical reaction below may represent a method of synthesis:

204
80Hg + 136
54Xe → 298
114Fl + 40
20Ca + 2 1
0

Recently it has been shown that the multi-nucleon transfer reactions in collisions of actinide nuclei (such as uranium and curium) might be used to synthesize the neutron-rich superheavy nuclei located at the island of stability.^[20]

It is also possible that ²⁹⁸Fl can be synthesized by the alpha decay of a massive nucleus. Such a method would depend highly on the SF stability of such nuclei, since the alpha half-lives are expected to be very short. The yields for such reactions will also most likely be extremely small. One such reaction is:

244
94Pu(96
40Zr, 2n) → 338
134Utq → 298
114Fl + 10 4
2He

References

• Isotope masses from:
  • M. Wang; G. Audi; A. H. Wapstra; F. G. Kondev; M. MacCormick; X. Xu; et al. (2012). "The AME2012 atomic mass evaluation (II). Tables, graphs and references." (PDF). Chinese Physics C. 36 (12): 1603–2014. Bibcode:2012ChPhC..36....3M. doi:10.1088/1674-1137/36/12/003. 
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. 
• Isotopic compositions and standard atomic masses from:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683. 
  • M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary. 
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. 
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005.  Check date values in: |access-date= (help)
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9. 

Isotopes of the chemical elements
1 H																	2 He
3 Li	4 Be											5 B	6 C	7 N	8 O	9 F	10 Ne
11 Na	12 Mg											13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
19 K	20 Ca	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
37 Rb	38 Sr	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
55 Cs	56 Ba		72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
87 Fr	88 Ra		104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Nh	114 Fl	115 Mc	116 Lv	117 Ts	118 Og
		57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu
		89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr
Table of nuclides Categories: Isotopes Tables of nuclides Metastable isotopes Isotopes by element