Isotopes of ununtrium

Ununtrium (Uut) 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 ²⁸⁴Uut as a decay product of ²⁸⁸Uup in 2003. The first isotope to be directly synthesized was ²⁷⁸Uut in 2004. There are 6 known radioisotopes from ²⁷⁸Uut to ²⁸⁶Uut. The longest-lived isotope is ²⁸⁶Uut with a half-life of 19.6 seconds.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin
278Uut	113	165	278.17058(20)#	340 µs	α	274Rg
282Uut	113	169	282.17567(39)#	73 ms	α	278Rg
283Uut	113	170	283.17657(52)#	100(+490-45) ms	α	279Rg
284Uut	113	171	284.17873(62)#	0.48(+58-17) s	α	280Rg
285Uut	113	172	285.17973(89)#	5.5 s	α	281Rg
286Uut	113	173	286.18221(72)#	19.6 s	α	282Rg

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.

Isotopes and nuclear properties

Nucleosynthesis

Target-projectile combinations leading to Z=113 compound nuclei

The below table contains various combinations of targets and projectiles (both at max no. of neutrons) which could be used to form compound nuclei with an atomic number of 113.

Target	Projectile	CN	Attempt result
208Pb	71Ga	279Uut	Reaction yet to be attempted
209Bi	70Zn	279Uut	Successful reaction
232Th	51V	283Uut	Reaction yet to be attempted
238U	45Sc	283Uut	Reaction yet to be attempted
237Np	48Ca	285Uut	Successful reaction
244Pu	41K	285Uut	Reaction yet to be attempted
243Am	40Ar	283Uut	Reaction yet to be attempted
248Cm	37Cl	285Uut	Reaction yet to be attempted
249Bk	36S	285Uut	Reaction yet to be attempted
249Cf	31P	280Uut	Reaction yet to be attempted

Cold fusion

This section deals with the synthesis of nuclei of ununtrium 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.

²⁰⁹Bi(⁷⁰Zn,xn)^279-xUut (x=1)

The synthesis of ununtrium was first attempted in 1998 by the team at GSI using the above cold fusion reaction. In two separate runs, they were unable to detect any atoms and calculated a cross section limit of 900 fb. They repeated the experiment in 2003 and lowered the limit further to 400 fb. In late 2003, the emerging team at RIKEN using their efficient apparatus GARIS attempted the reaction and reached a limit of 140 fb. In December 2003 – August 2004, they resorted to 'brute force' and performed an eight-month-long irradiation in which they increased the sensitivity to 51 fb. They were able to detect a single atom of ²⁷⁸Uut. They repeated the reaction in several runs in 2005 and were able to synthesize a second atom. They calculated a record-low 31 fb for the cross section for the 2 atoms. The reaction was repeated again in 2006 with two long production runs but no further atoms were detected. This lowered the yield further to the current value of just 23 fb.

Hot fusion

This section deals with the synthesis of nuclei of ununtrium 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.

²³⁷Np(⁴⁸Ca,xn)^285-xUut (x=3)

In June 2006, the Dubna-Livermore team synthesised ununtrium directly in the "warm" fusion reaction between neptunium-237 and calcium-48 nuclei. Two atoms of²⁸²Uut were detected with a cross section of 900 fb.

As a decay product

Ununtrium has also been detected in the decay of ununpentium and ununseptium.

Chronology of isotope discovery

Isotope	Year discovered	Discovery reaction
278Uut	2004	209Bi(70Zn,n)
279Uut	unknown
280Uut	unknown
281Uut	unknown
282Uut	2006	237Np(48Ca,3n)
283Uut	2003	243Am(48Ca,4n)
284Uut	2003	243Am(48Ca,3n)
285Uut	2009	249Bk(48Ca,4n)
286Uut	2009	249Bk(48Ca,3n)

Yields of isotopes

Cold fusion

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

Projectile	Target	CN	1n	2n	3n
70Zn	209Bi	279Uut	23 fb

Hot fusion

The table below provides cross-sections and excitation energies for hot fusion reactions producing ununtrium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Projectile	Target	CN	3n	4n	5n
48Ca	237Np	285Uut	0.9 pb, 39.1 MeV

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	70Zn	279Uut	1n (278Uut)	30 fb	DNS
237Np	48Ca	285Uut	3n (282Uut)	0.4 pb	DNS

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.". Chinese Physics C, 36 (12): 1603–2014. doi:10.1088/1674-1137/36/12/003. 
  • G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". 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 and 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 and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". 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. 
  • 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. 

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