Isotopes of ununseptium

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Ununseptium (Uus) is the most-recently synthesized artificial element, and much of the data is hypothetical. As any artificial element, a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first (and so far only) isotopes to be synthesized were 293Uus and 294Uus in 2009. The longer-lived isotope is 294Uus with a half-life of 51 ms.

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay mode(s) daughter
isotope(s)
nuclear
spin
293Uus 117 176 293.20824(89)# 22 (+8, -4) ms[1] α 289Uup
294Uus 117 177 294.21046(74)# 51 (+41, -16) ms[2] α 290Uup

Notes[edit]

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values from Ame2003 denote one standard deviation. Values from IUPAC are expanded uncertainties.

Isotopes and nuclear properties[edit]

Nucleosynthesis[edit]

Target-projectile combinations leading to Z=117 compound nuclei[edit]

The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with atomic number 117.

Target Projectile CN Attempt result
153Eu 136Xe 289Uus Reaction yet to be attempted
208Pb 81Br 289Uus Reaction yet to be attempted
209Bi 82Se 291Uus Reaction yet to be attempted
232Th 59Co 291Uus Reaction yet to be attempted
231Pa 58Fe 289Uus Reaction yet to be attempted
238U 55Mn 293Uus Reaction yet to be attempted
237Np 54Cr 291Uus Reaction yet to be attempted
244Pu 51V 295Uus Reaction yet to be attempted
243Am 50Ti 293Uus Reaction yet to be attempted
248Cm 45Sc 293Uus Reaction yet to be attempted
250Cm 45Sc 295Uus Reaction yet to be attempted
249Bk 48Ca 297Uus Successful reaction
249Cf 41K 290Uus Reaction yet to be attempted
252Cf 41K 293Uus Reaction yet to be attempted
253Es 40Ar 293Uus Reaction yet to be attempted

Hot fusion[edit]

249Bk (48Ca, xn)297-xUus (x=3,4)[edit]

Between July 2009 and February 2010, the team at the JINR (Flerov Laboratory of Nuclear Reactions) ran a 7-month-long experiment to synthesize ununseptium using the reaction above.[3] The expected cross-section was of the order of 2 pb. The expected evaporation residues, 293Uus and 294Uus, were predicted to decay via relatively long decay chains as far as isotopes of dubnium or lawrencium.


The team published a scientific paper in April 2010 (first results were presented in January 2010[5]) that six atoms of the neighbouring isotopes 294Uus (one atom) and 293Uus (five atoms) were detected. The heavier isotope decayed by the successive emission of six alpha particles down as far as the new isotope 270Db which underwent apparent spontaneous fission. On the other hand, the lighter odd-even isotope decayed by the emission of just three alpha particles, as far as 281Rg, which underwent spontaneous fission. The reaction was run at two different excitation energies of 35 MeV (dose 2x1019) and 39 MeV (dose 2.4×1019). Initial decay data was published as a preliminary presentation on the JINR website.[6]

A further experiment in May 2010, looking at the chemistry of one of the decay products, ununtrium, identified a further two atoms derived from 294Uus.

Chronology of isotope discovery[edit]

Isotope Year discovered Discovery reaction
294Uus 2009 249Bk(48Ca,3n)
293Uus 2009 249Bk(48Ca,4n)

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.

DNS = Di-nuclear system; σ = cross section

Target Projectile CN Channel (product) σmax Model Ref
209Bi 82Se 291Uus 1n (290Uus) 15 fb DNS [7]
209Bi 79Se 288Uus 1n (287Uus) 0.2 pb DNS [7]
232Th 59Co 291Uus 2n (289Uus) 0.1 pb DNS [7]
238U 55Mn 293Uus 2-3n (291,290Uus) 70 fb DNS [7]
244Pu 51V 295Uus 3n (292Uus) 0.6 pb DNS [7]
248Cm 45Sc 293Uus 4n (289Uus) 2.9 pb DNS [7]
246Cm 45Sc 291Uus 4n (287Uus) 1 pb DNS [7]
249Bk 48Ca 297Uus 3n (294Uus) 2.1 pb ; 3 pb DNS [7][8]
247Bk 48Ca 295Uus 3n (292Uus) 0.8, 0.9 pb DNS [7][8]

Decay characteristics[edit]

Theoretical calculations in a quantum tunneling model with mass estimates from a macroscopic-microscopic model predict the alpha-decay half-lives of isotopes of ununseptium (namely, 289–303Uus) to be around 0.1–40 ms.[9][10][11]

References[edit]

  1. ^ Oganessian, Yu. Ts.; et al. (2013). "Experimental studies of the 249Bk + 48Ca reaction including decay properties and excitation function for isotopes of element 117, and discovery of the new isotope 277Mt". Physical Review C 87 (5): 054621. Bibcode:2013PhRvC..87e4621O. doi:10.1103/PhysRevC.87.054621. 
  2. ^ Khuyagbaatar, J.; Yakushev, A.; Düllmann, Ch. E.; "et al." (2014). "48Ca+249Bk Fusion Reaction Leading to Element Z=117: Long-Lived α-Decaying 270Db and Discovery of 266Lr". Physical Review Letters 112 (17): 172501. doi:10.1103/PhysRevLett.112.172501. 
  3. ^ Ununseptium – the 117th element at AtomInfo.ru
  4. ^ a b Roman Sagaidak. "Experiment setting on synthesis of superheavy nuclei in fusion-evaporation reactions. Preparation to synthesis of new element with Z=117". Retrieved 2009-07-07. 
  5. ^ Recommendations: 31st meeting, PAC for Nuclear Physics
  6. ^ Walter Grenier: Recommendations, a PowerPoint presentation at the January 2010 meeting of the PAC for Nuclear Physics
  7. ^ a b c d e f g h i Zhao-Qing, Feng; Gen-Ming, Jin; Ming-Hui, Huang; Zai-Guo, Gan; Nan, Wang; Jun-Qing, Li (2007). "Possible Way to Synthesize Superheavy Element Z = 117". Chinese Physics Letters 24 (9): 2551. arXiv:0708.0159. Bibcode:2007ChPhL..24.2551F. doi:10.1088/0256-307X/24/9/024. 
  8. ^ a b 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. 
  9. ^ C. Samanta, P. Roy Chowdhury and D.N. Basu (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nucl. Phys. A 789: 142. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. doi:10.1016/j.nuclphysa.2007.04.001. 
  10. ^ P. Roy Chowdhury, C. Samanta, and D. N. 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. 
  11. ^ P. Roy Chowdhury, C. Samanta, and D. N. 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. 

External sources[edit]


Isotopes of livermorium Isotopes of ununseptium Isotopes of ununoctium
Table of nuclides