Isotopes of flerovium

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Flerovium (Fl) is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 289Fl in 1999 (or possibly 1998). Flerovium has five confirmed isotopes, and possibly 2 nuclear isomers. The longest-lived isotope is 289Fl with a half-life of 2.6 seconds.

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay mode(s)[n 1] daughter
isotope(s)
nuclear
spin
excitation energy
285Fl 114 171 285.18364(47)# 125 ms α 281Cn 3/2+#
286Fl[n 2] 114 172 286.18424(71)# 130 ms SF (60%)[n 3] (variable) 0+
α (40%) 282Cn
287Fl 114 173 287.18678(66)# 510(+180-100) ms α 283Cn
287mFl[n 4] 5.5s α 283Cn
288Fl 114 174 288.18757(91)# .8(+27-16) s α 284Cn 0+
289Fl 114 175 289.19042(60)# 2.6(+12-7) s α 285Cn 5/2+#
289mFl[n 4] 1.1 min α 285Cn
  1. ^ Abbreviations:
    SF: Spontaneous fission
  2. ^ Not directly synthesized, produced in decay chain of 294Uuo
  3. ^ Heaviest nuclide known to undergo spontaneous fission
  4. ^ a b Existence of this isomer is uncertain

Notes[edit]

  • 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[edit]

Nucleosynthesis[edit]

Target-projectile combinations leading to Z=114 compound nuclei[edit]

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 result
208Pb 76Ge 284Fl Failure to date
232Th 54Cr 286Fl Reaction yet to be attempted
238U 50Ti 288Fl Reaction yet to be attempted
244Pu 48Ca 292Fl Successful reaction
242Pu 48Ca 290Fl Successful reaction
239Pu 48Ca 287Fl Reaction yet to be attempted
248Cm 40Ar 288Fl Reaction yet to be attempted
249Cf 36S 285Fl Reaction yet to be attempted

Cold fusion[edit]

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[edit]

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. 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[edit]

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)[edit]

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
.[1] The reaction was repeated in 1999 and a further two atoms of flerovium were detected. The products were assigned to 288
Fl
.[2] 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.[3] 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 of288
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 ununseptium. 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.[4]

242Pu(48Ca,xn)290−xFl (x=2,3,4,5)[edit]

The team at Dubna first studied this reaction in March–April 1999 and detected two atoms of flerovium, assigned to 287Fl.[5] The reaction was repeated in September 2003 in order to attempt to confirm the decay data for 287Fl and 283Cn since conflicting data for283Cn 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. [6][7]

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, as287
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.[8]

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[edit]

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

As a decay product[edit]

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

Evaporation residue Observed Fl isotope
293Lv 289Fl [7][9]
292Lv 288Fl [7]
291Lv 287Fl [3]
294Uuo, 290Lv 286Fl [10]

Retracted isotopes[edit]

285Fl[edit]

In the claimed synthesis of 293Uuo 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[edit]

Isotope Year discovered Discovery reaction
285Fl 2010 242Pu(48Ca,5n)
286Fl 2002 249Cf(48Ca,3n) [10]
287aFl 2002 244Pu(48Ca,5n)
287bFl ?? 1999 242Pu(48Ca,3n)
288Fl 2002 244Pu(48Ca,4n)
289aFl 1999 244Pu(48Ca,3n)
289bFl ? 1998 244Pu(48Ca,3n)

Fission of compound nuclei with an atomic number of 114[edit]

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.[11]

Nuclear isomerism[edit]

289Fl[edit]

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[edit]

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[edit]

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[edit]

Projectile Target CN 1n 2n 3n
76Ge 208Pb 284Fl <1.2 pb

Hot fusion[edit]

Projectile Target CN 2n 3n 4n 5n
48Ca 242Pu 290Fl 0.5 pb, 32.5 MeV 3.6 pb, 40.0 MeV 4.5 pb, 40.0 MeV <1.4 pb, 45.0 MeV
48Ca 244Pu 292Fl 1.7 pb, 40.0 MeV 5.3 pb, 40.0 MeV 1.1 pb, 52.0 MeV

Theoretical calculations[edit]

Evaporation residue cross sections[edit]

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

Target Projectile CN Channel (product) σmax Model Ref
208Pb 76Ge 284Fl 1n (283Fl) 60 fb DNS [12]
208Pb 73Ge 281Fl 1n (280Fl) 0.2 pb DNS [12]
238U 50Ti 288Fl 2n (286Fl) 60 fb DNS [13]
244Pu 48Ca 292Fl 4n (288Fl) 4 pb MD [14]
242Pu 48Ca 290Fl 3n (287Fl) 3 pb MD [14]

Decay characteristics[edit]

Theoretical estimation of the alpha decay half-lives of the isotopes of the flerovium supports the experimental data.[15][16] The fission-survived isotope 298Fl is predicted to have alpha decay half-life around 17 days.[17][18]

In search for the island of stability: 298Fl[edit]

According to macroscopic-microscopic (MM) theory[citation needed], 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 297Uup, 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.[citation needed] 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 Qalpha 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[edit]

While evidence for closed neutron shells can be deemed directly from the systematic variation of Qalpha 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 pairings282Cn (TSF1/2 = 0.8 ms) and 286Fl (TSF1/2 = 130 ms), and 284Cn (TSF = 97 ms) and288Fl (TSF >800 ms). Further evidence would come from the measurement of partial SF half-lives of nuclei with Z>114, such as290Lv and 292Uuo (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[edit]

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
80
Hg
+ 136
54
Xe
298
114
Fl
+ 40
20
Ca
+ 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.[19]

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

References[edit]

  1. ^ Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Shirokovsky, I.; Tsyganov, Yu.; Gulbekian, G.; Bogomolov, S.; Gikal, B.; Mezentsev, A.; Iliev, S.; Subbotin, V.; Sukhov, A.; Buklanov, G.; Subotic, K.; Itkis, M.; Moody, K.; Wild, J.; Stoyer, N.; Stoyer, M.; Lougheed, R. (1999). "Synthesis of Superheavy Nuclei in the ^{48}Ca+ ^{244}Pu Reaction". Physical Review Letters 83 (16): 3154. Bibcode:1999PhRvL..83.3154O. doi:10.1103/PhysRevLett.83.3154. 
  2. ^ Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Shirokovsky, I.; Tsyganov, Yu.; Gulbekian, G.; Bogomolov, S. et al. (2000). "Synthesis of superheavy nuclei in the 48Ca+244Pu reaction: 288Fl". Physical Review C 62 (4): 041604. Bibcode:2000PhRvC..62d1604O. doi:10.1103/PhysRevC.62.041604. 
  3. ^ a b Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Shirokovsky, I.; Tsyganov, Yu.; Gulbekian, G.; Bogomolov, S. et al. (2004). "Measurements of cross sections for the fusion-evaporation reactions 244Pu(48Ca,xn)292−xFl and 245Cm(48Ca,xn)293−x116". Physical Review C 69 (5): 054607. Bibcode:2004PhRvC..69e4607O. doi:10.1103/PhysRevC.69.054607. 
  4. ^ Element 114 – Heaviest Element at GSI Observed at TASCA
  5. ^ Yeremin, A. V.; Oganessian, Yu. Ts.; Popeko, A. G.; Bogomolov, S. L.; Buklanov, G. V.; Chelnokov, M. L.; Chepigin, V. I.; Gikal, B. N.; Gorshkov, V. A. et al. (1999). "Synthesis of nuclei of the superheavy element 114 in reactions induced by 48Ca". Nature 400 (6741): 242. Bibcode:1999Natur.400..242O. doi:10.1038/22281. 
  6. ^ Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Shirokovsky, I.; Tsyganov, Yu.; Gulbekian, G.; Bogomolov, S. et al. (2004). "Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions233,238U, 242Pu, and 248Cm+48Ca". Physical Review C 70 (6): 064609. Bibcode:2004PhRvC..70f4609O. doi:10.1103/PhysRevC.70.064609. 
  7. ^ a b c "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
  8. ^ Stavsetra, L.; Gregorich, KE; Dvorak, J; Ellison, PA; Dragojević, I; Garcia, MA; Nitsche, H (2009). "Independent Verification of Element 114 Production in the 48Ca+242Pu Reaction". Physical Review Letters 103 (13): 132502. Bibcode:2009PhRvL.103m2502S. doi:10.1103/PhysRevLett.103.132502. PMID 19905506. 
  9. ^ see livermorium
  10. ^ a b see ununoctium
  11. ^ seeFlerov lab annual reports 2000–2006
  12. ^ a b Feng, Zhao-Qing; Jin, Gen-Ming; Li, Jun-Qing; Scheid, Werner (2007). "Formation of superheavy nuclei in cold fusion reactions". Physical Review C 76 (4): 044606. arXiv:0707.2588. Bibcode:2007PhRvC..76d4606F. doi:10.1103/PhysRevC.76.044606. 
  13. ^ Feng, Z; Jin, G; Li, J; Scheid, W (2009). "Production of heavy and superheavy nuclei in massive fusion reactions". Nuclear Physics A 816: 33. arXiv:0803.1117. Bibcode:2009NuPhA.816...33F. doi:10.1016/j.nuclphysa.2008.11.003. 
  14. ^ a b Zagrebaev, V (2004). "Fusion-fission dynamics of super-heavy element formation and decay" (PDF). Nuclear Physics A 734: 164. Bibcode:2004NuPhA.734..164Z. doi:10.1016/j.nuclphysa.2004.01.025. 
  15. ^ P. Roy Chowdhury, C. Samanta, and D. N. Basu; Samanta; Basu (January 26, 2006). "α decay half-lives of new superheavy elements". Phys. Rev. C 73: 014612. arXiv:nucl-th/0507054. Bibcode:2006PhRvC..73a4612C. doi:10.1103/PhysRevC.73.014612. 
  16. ^ C. Samanta, P. Roy Chowdhury and D.N. Basu; Chowdhury; Basu (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nucl. Phys. A 789: 142–154. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. doi:10.1016/j.nuclphysa.2007.04.001. 
  17. ^ P. Roy Chowdhury, C. Samanta, and D. N. Basu; Samanta; Basu (2008). "Search for long lived heaviest nuclei beyond the valley of stability". Phys. Rev. C 77 (4): 044603. arXiv:0802.3837. Bibcode:2008PhRvC..77d4603C. doi:10.1103/PhysRevC.77.044603. 
  18. ^ P. Roy Chowdhury, C. Samanta, and D. N. Basu; Samanta; Basu (2008). "Nuclear half-lives for α-radioactivity of elements with 100 ≤ Z ≤ 130". At. Data & Nucl. Data Tables 94 (6): 781–806. arXiv:0802.4161. Bibcode:2008ADNDT..94..781C. doi:10.1016/j.adt.2008.01.003. 
  19. ^ Zagrebaev, V; Greiner, W; Greiner (2008). "Synthesis of superheavy nuclei: A search for new production reactions". Physical Review C 78 (3): 034610. arXiv:0807.2537. Bibcode:2008PhRvC..78c4610Z. doi:10.1103/PhysRevC.78.034610. 


Isotopes of ununtrium Isotopes of flerovium Isotopes of ununpentium
Table of nuclides