Isotopes of ununseptium

Ununseptium (Uus) is the most-recently synthesized synthetic element, and much of the data is hypothetical. As any synthetic element, a standard atomic mass cannot be given. Like all synthetic 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

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

• 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

Nucleosynthesis

Target-projectile combinations leading to Z=117 compound nuclei

The below table contains various combinations of targets and projectiles that 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

²⁴⁹Bk (⁴⁸Ca, xn)^297−xUus (x=3,4)

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.

• 

  Calculated decay chains from the parent nuclei ²⁹³Uus and ²⁹⁴ Uus^[1]

• 

  Calculated excitation function for the production of the compound nucleus ²⁹⁷Uus from the reaction²⁴⁹Bk (⁴⁸Ca,xn)^[1]

1. ^ ^{a b} Roman Sagaidak. "Experiment setting on synthesis of superheavy nuclei in fusion-evaporation reactions. Preparation to synthesis of new element with Z=117" (PDF). Retrieved 2009-07-07.

The team published a scientific paper in April 2010 (first results were presented in January 2010^[4]) 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 2×10¹⁹) and 39 MeV (dose 2.4×10¹⁹). Initial decay data was published as a preliminary presentation on the JINR website.^[5]

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

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

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.

DNS = Di-nuclear system; σ = cross section

Target	Projectile	CN	Channel (product)	σmax	Model	Ref
^209Bi	^82Se	^291Uus	1n (^290Uus)	15 fb	DNS	[6]
^209Bi	^79Se	^288Uus	1n (^287Uus)	0.2 pb	DNS	[6]
^232Th	^59Co	^291Uus	2n (^289Uus)	0.1 pb	DNS	[6]
^238U	^55Mn	^293Uus	2-3n (^291,290Uus)	70 fb	DNS	[6]
^244Pu	^51V	^295Uus	3n (^292Uus)	0.6 pb	DNS	[6]
^248Cm	^45Sc	^293Uus	4n (^289Uus)	2.9 pb	DNS	[6]
^246Cm	^45Sc	^291Uus	4n (^287Uus)	1 pb	DNS	[6]
^249Bk	^48Ca	^297Uus	3n (^294Uus)	2.1 pb ; 3 pb	DNS	[6][7]
^247Bk	^48Ca	^295Uus	3n (^292Uus)	0.8, 0.9 pb	DNS	[6][7]

Decay characteristics

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.^[8][9][10]

References

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. Recommendations: 31st meeting, PAC for Nuclear Physics
5. Walter Grenier: Recommendations, a PowerPoint presentation at the January 2010 meeting of the PAC for Nuclear Physics
6. 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.
7. 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.
8. C. Samanta; P. Roy Chowdhury; D. N. Basu (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nuclear Physics A 789: 142. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. doi:10.1016/j.nuclphysa.2007.04.001.
9. P. Roy Chowdhury; C. Samanta; D. N. Basu (2008). "Search for long lived heaviest nuclei beyond the valley of stability". Physical Review C 77 (4): 044603. arXiv:0802.3837. Bibcode:2008PhRvC..77d4603C. doi:10.1103/PhysRevC.77.044603.
10. P. Roy Chowdhury; C. Samanta; D. N. Basu (2008). "Nuclear half-lives for α -radioactivity of elements with 100 ≤ Z ≤ 130". Atomic Data and Nuclear Data Tables 94 (6): 781–806. arXiv:0802.4161. Bibcode:2008ADNDT..94..781C. doi:10.1016/j.adt.2008.01.003.

External sources

• 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)" (PDF). Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683.