Isotopes of nihonium

Nihonium (₁₁₃Nh) is a synthetic element. Being synthetic, a standard atomic weight cannot be given and like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was ²⁸⁴Nh as a decay product of ²⁸⁸Mc in 2003. The first isotope to be directly synthesized was ²⁷⁸Nh in 2004. There are 6 known radioisotopes from ²⁷⁸Nh to ²⁸⁶Nh, along with the unconfirmed ²⁸⁷Nh and ²⁹⁰Nh. The longest-lived isotope is ²⁸⁶Nh with a half-life of 9.5 seconds.

Isotopes of nihonium (₁₁₃Nh)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 278Nh synth 2.0 ms α 274Rg 282Nh synth 61 ms α 278Rg 283Nh synth 123 ms α 279Rg 284Nh synth 0.90 s α 280Rg ε 284Cn 285Nh synth 2.1 s α 281Rg SF – 286Nh synth 9.5 s α 282Rg 287Nh synth 5.5 s?[2] α 283Rg 290Nh synth 2 s?[3] α 286Rg

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List of isotopes

Nuclide	Z	N	Isotopic mass (Da)[4] [n 1][n 2]	Half-life[1]	Decay mode[1] [n 3]	Daughter isotope	Spin and parity[1]
278Nh	113	165	278.17073(24)#	2.0+2.7 −0.7 ms [2.3(13) ms]	α	274Rg
282Nh	113	169	282.17577(43)#	61+73 −22 ms[5]	α	278Rg
283Nh[n 4]	113	170	283.17667(47)#	123+80 −35 ms[5]	α	279Rg
284Nh[n 5]	113	171	284.17884(57)#	0.90+0.07 −0.06 s[5]	α (≥99%)	280Rg
					EC (≤1%)[5]	284Cn
285Nh[n 6]	113	172	285.18011(83)#	2.1+0.6 −0.3 s[5]	α (82%)	281Rg
					SF (18%)[5]	(various)
286Nh[n 7]	113	173	286.18246(63)#	9.5+6.3 −2.7 s [12(5) s]	α	282Rg
287Nh[2][n 8]	113	174	287.18406(76)#	5.5 s	α	283Rg
290Nh[n 9]	113	177	290.19143(50)#	2.0+9.6 −0.9 s [8(6) s]	α	286Rg
					SF (<50%)	(various)
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1. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
2. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
3. Modes of decay:

   EC:	Electron capture

4. Not directly synthesized, occurs as decay product of ²⁸⁷Mc
5. Not directly synthesized, occurs as decay product of ²⁸⁸Mc
6. Not directly synthesized, occurs in decay chain of ²⁹³Ts
7. Not directly synthesized, occurs in decay chain of ²⁹⁴Ts
8. Not directly synthesized, occurs in decay chain of ²⁸⁷Fl; unconfirmed
9. Not directly synthesized, occurs in decay chain of ²⁹⁰Fl and ²⁹⁴Lv; unconfirmed

Isotopes and nuclear properties

Nucleosynthesis

Super-heavy elements such as nihonium are produced by bombarding lighter elements in particle accelerators that induce fusion reactions. Whereas most of the isotopes of nihonium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers.^[6]

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.^[7] 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.^[6] The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).^[8]

Cold fusion

Before the synthesis of nihonium by the RIKEN team, scientists at the Institute for Heavy Ion Research (Gesellschaft für Schwerionenforschung) in Darmstadt, Germany also tried to synthesize nihonium by bombarding bismuth-209 with zinc-70 in 1998. No nihonium atoms were identified in two separate runs of the reaction.^[9] They repeated the experiment in 2003 again without success.^[9] 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 ²⁷⁸Nh.^[10] They repeated the reaction in several runs in 2005 and were able to synthesize a second atom,^[11] followed by a third in 2012.^[12]

The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=113.

Target	Projectile	CN	Attempt result
208Pb	71Ga	279Nh	Reaction yet to be attempted
209Bi	70Zn	279Nh	Successful reaction
238U	45Sc	283Nh	Reaction yet to be attempted
237Np	48Ca	285Nh	Successful reaction
244Pu	41K	285Nh	Reaction yet to be attempted
250Cm	37Cl	287Nh	Reaction yet to be attempted
248Cm	37Cl	285Nh	Reaction yet to be attempted

Hot fusion

In June 2006, the Dubna-Livermore team synthesised nihonium directly by bombarding a neptunium-237 target with accelerated calcium-48 nuclei, in a search for the lighter isotopes ²⁸¹Nh and ²⁸²Nh and their decay products, to provide insight into the stabilizing effects of the closed neutron shells at N = 162 and N = 184:^[13]

²³⁷
₉₃Np + ⁴⁸
₂₀Ca → ²⁸²
₁₁₃Nh + 3 ¹
₀n

Two atoms of ²⁸²Nh were detected.^[13]

As decay product

List of nihonium isotopes observed by decay

Evaporation residue	Observed nihonium isotope
294Lv, 290Fl ?	290Nh ?[3]
287Fl ?	287Nh ?[2]
294Ts, 290Mc	286Nh[14]
293Ts, 289Mc	285Nh[14]
288Mc	284Nh[15]
287Mc	283Nh[15]
286Mc	282Nh

Nihonium has been observed as a decay product of moscovium (via alpha decay). Moscovium currently has five known isotopes; all of them undergo alpha decays to become nihonium nuclei, with mass numbers between 282 and 286. Parent moscovium nuclei can be themselves decay products of tennessine. It may also occur as a decay product of flerovium (via electron capture), and parent flerovium nuclei can be themselves decay products of livermorium.^[16] For example, in January 2010, the Dubna team (JINR) identified nihonium-286 as a product in the decay of tennessine via an alpha decay sequence:^[14]

²⁹⁴
₁₁₇Ts → ²⁹⁰
₁₁₅Mc + ⁴
₂He

²⁹⁰
₁₁₅Mc → ²⁸⁶
₁₁₃Nh + 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	279Nh	1n (278Nh)	30 fb	DNS	[17]
238U	45Sc	283Nh	3n (280Nh)	20 fb	DNS	[18]
237Np	48Ca	285Nh	3n (282Nh)	0.4 pb	DNS	[19]
244Pu	41K	285Nh	3n (282Nh)	42.2 fb	DNS	[18]
250Cm	37Cl	287Nh	4n (283Nh)	0.594 pb	DNS	[18]
248Cm	37Cl	285Nh	3n (282Nh)	0.26 pb	DNS	[18]