Isotopes of ununtrium

Ununtrium (Uut, element 113) is a synthetic element with atomic number 113. Being synthetic, a standard atomic mass cannot be given and 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

Super-heavy elements such as ununtrium are produced by bombarding lighter elements in particle accelerators that induce fusion reactions. Whereas most of the isotopes of ununtrium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers.

Depending on the energies involved, the former are separated into "hot" and "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets (actinides), giving rise to compound nuclei at high excitation energy (~40–50 MeV) that may either fission or evaporate several (3 to 5) neutrons. In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20 MeV), which decreases the probability that these products will undergo fission reactions. As the fused nuclei cool to the ground state, they require emission of only one or two neutrons, and thus, allows for the generation of more neutron-rich products. The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).

Cold fusion

Before the successful synthesis of ununtrium by the RIKEN team, scientists at the Institute for Heavy Ion Research (Gesellschaft für Schwerionenforschung) in Darmstadt, Germany also tried to synthesize ununtrium by bombarding bismuth-209 with zinc-70 in 1998. No ununtrium atoms were identified in two separate runs of the reaction. They repeated the experiment in 2003 again without success. 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 carried out the reaction for a period of eight months. 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.

Hot fusion

In June 2006, the Dubna-Livermore team synthesised ununtrium directly by bombarding a neptunium-237 target with accelerated calcium-48 nuclei:

237
93Np + 48
20Ca → 282
113Uut + 1
0n

Two atoms of ²⁸²Uut were detected.

As decay product

List of ununtrium isotopes observed by decay

Evaporation residue	Observed ununtrium isotope
294Uus, 290Uup	286Uut
293Uus, 289Uup	285Uut
288Uup	284Uut
287Uup	283Uut

Ununtrium has been observed as decay products of ununpentium. Ununpentium currently has four known isotopes; all of them undergo alpha decays to become ununtrium nuclei, with mass numbers between 283 and 286. Parent ununpentium nuclei can be themselves decay products of ununseptium. To date, no other elements have been known to decay to ununtrium. For example, in January 2010, the Dubna team (JINR) identified ununtrium-286 as a product in the decay of ununseptium via an alpha decay sequence:

294
117Uus → 290
115Uup + 4
2He

290
115Uup → 286
113Uut + 4
2He

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:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.

Isotopes of copernicium	Isotopes of ununtrium	Isotopes of flerovium
Table of nuclides