Isotopes of nihonium

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Main isotopes of nihonium (113Nh)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
278Nh syn 1.4 ms α 274Rg
282Nh syn 73 ms α 278Rg
283Nh syn 75 ms α 279Rg
284Nh syn 0.91 s α 280Rg
EC 284Cn
285Nh syn 4.2 s α 281Rg
286Nh syn 9.5 s α 282Rg
287Nh[1] syn 5.5 s? α 283Rg
290Nh[2] syn 2 s? α 286Rg
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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 8 seconds.

List of isotopes[]

Nuclide
 Z N Isotopic mass (Da)
[n 1][n 2] 		Half-life
 Decay
mode
[n 3] 		Daughter
isotope
 Spin and
parity
278Nh 113 165 278.17058(20)# 1.4 ms α 274Rg
282Nh 113 169 282.17567(39)# 73 ms α 278Rg
283Nh[n 4] 113 170 283.17657(52)# 75 ms α 279Rg
284Nh[n 5] 113 171 284.17873(62)# 0.91 s α (96.8%) 280Rg  
EC (3.2%)[3] 284Cn
285Nh[n 6] 113 172 285.17973(89)# 4.2 s α 281Rg
286Nh[n 7] 113 173 286.18221(72)# 9.5 s α 282Rg
287Nh[n 8] 113 174 287.18339(81)# 5.5 s α 283Rg
290Nh[n 9] 113 177 2 s? α 286Rg
This table header & footer:
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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.[4]

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.[5] 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.[4] The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).[6]

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.[7] They repeated the experiment in 2003 again without success.[7] 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.[8] They repeated the reaction in several runs in 2005 and were able to synthesize a second atom,[9] followed by a third in 2012.[10]

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:[11]

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

Two atoms of 282Nh were detected.[11]

As decay product[]

List of nihonium isotopes observed by decay
Evaporation residue Observed nihonium isotope
294Lv, 290Fl ? 290Nh ?[2]
287Fl ? 287Nh ?[1]
294Ts, 290Mc 286Nh[12]
293Ts, 289Mc 285Nh[12]
288Mc 284Nh[13]
287Mc 283Nh[13]

Nihonium has been observed as a decay product of moscovium (via alpha decay). Moscovium currently has four known isotopes; all of them undergo alpha decays to become nihonium nuclei, with mass numbers between 283 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. To date, no other elements have been known to decay to nihonium.[14] 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:[12]

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 [15]
238U 45Sc 283Nh 3n (280Nh) 20 fb DNS [16]
237Np 48Ca 285Nh 3n (282Nh) 0.4 pb DNS [17]
244Pu 41K 285Nh 3n (282Nh) 42.2 fb DNS [16]
250Cm 37Cl 287Nh 4n (283Nh) 0.594 pb DNS [16]
248Cm 37Cl 285Nh 3n (282Nh) 0.26 pb DNS [16]

References[]

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