Isotopes of ununoctium

Ununoctium (Uuo) is an synthetic element created in particle colliders, and thus a standard atomic mass cannot be given. Like all synthetic elements, it has no stable isotopes. The first (and so far only) isotope to be synthesized was ²⁹⁴Uuo in 2006; it has a half-life of 890 microseconds.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin
^294Uuo	118	176	294.21392(71)#	890 µs	α	^290Lv

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.

Theoretical

Theoretical calculations done on the synthetic pathways for, and the half-life of, other isotopes have shown that some could be slightly more stable than the synthesized isotope ²⁹⁴Uuo, most likely ²⁹³Uuo, ²⁹⁵Uuo, ²⁹⁶Uuo, ²⁹⁷Uuo, ²⁹⁸Uuo, ³⁰⁰Uuo and ³⁰²Uuo.^[1][2][3] Of these, ²⁹⁷Uuo, might provide the best chances for obtaining longer-lived nuclei,^[1][3] and thus might become the focus of future work with this element. Some isotopes with many more neutrons, such as some located around ³¹³Uuo, could also provide longer-lived nuclei.^[4]

Target-projectile combinations leading to Z=118 compound nuclei

The below table contains various combinations of targets and projectiles that could be used to form compound nuclei with Z=118.

Target	Projectile	CN	Attempt result
^160Gd	^136Xe	^296Uuo*	Reaction yet to be attempted
^208Pb	^86Kr	^294Uuo*	Failure to date
^232Th	^64Ni	^296Uuo*	Reaction yet to be attempted
^238U	^58Fe	^296Uuo*	Reaction yet to be attempted
^244Pu	^54Cr	^298Uuo*	Reaction yet to be attempted
^248Cm	^50Ti	^298Uuo*	Reaction yet to be attempted
^250Cm	^50Ti	^300Uuo*	Reaction yet to be attempted
^249Cf	^48Ca	^297Uuo*	Successful reaction
^252Cf	^48Ca	^300Uuo*	Reaction yet to be attempted
^257Fm	^40Ar	^297Uuo*	Reaction yet to be attempted

Theoretical calculations on evaporation 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)	σ max	Model	Ref
^208Pb	^86Kr	^294Uuo	1n (^293Uuo)	0.1 pb	DNS	[5]
^208Pb	^85Kr	^293Uuo	1n (^292Uuo)	0.18 pb	DNS	[5]
^252Cf	^48Ca	^300Uuo	3n (^297Uuo)	1.2 pb	DNS	[6]
^251Cf	^48Ca	^299Uuo	3n (^296Uuo)	1.2 pb	DNS	[6]
^249Cf	^48Ca	^297Uuo	3n (^294Uuo)	0.3 pb	DNS	[6]

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 (1): 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.

1. P. Roy Chowdhury; C. Samanta; D. N. Basu (January 26, 2006). "α decay half-lives of new superheavy elements". Physical Review C 73: 014612. arXiv:nucl-th/0507054. Bibcode:2006PhRvC..73a4612C. doi:10.1103/PhysRevC.73.014612. Retrieved 2008-01-18.
2. C. Samanta; P. Roy Chowdhury; D. N. Basu (April 6, 2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nuclear Physics A 789 (1–4): 142–154. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. doi:10.1016/j.nuclphysa.2007.04.001. Retrieved 2008-01-18.
3. G. Royer; K. Zbiri; C. Bonilla (2004). "Entrance channels and alpha decay half-lives of the heaviest elements". Nuclear Physics A 730 (3–4): 355–376. arXiv:nucl-th/0410048. Bibcode:2004NuPhA.730..355R. doi:10.1016/j.nuclphysa.2003.11.010. Retrieved 2008-01-18.
4. S. B. Duarte; O. A. P. Tavares; M. Gonçalves; O. Rodríguez; F. Guzmán; T. N. Barbosa; F. García; A. Dimarco (2004). "Half-life predictions for decay modes of superheavy nuclei". Journal of Physics G: Nuclear and Particle Physics 30 (10): 1487–1494. Bibcode:2004JPhG...30.1487D. doi:10.1088/0954-3899/30/10/014. Retrieved 2008-01-18.
5. 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.
6. Feng, Z; Jin, G; Li, J; Scheid, W (2009). "Production of heavy and superheavy nuclei in massive fusion reactions". Nuclear Physics A 816 (1–4): 33–51. arXiv:0803.1117. Bibcode:2009NuPhA.816...33F. doi:10.1016/j.nuclphysa.2008.11.003.