Isotopes of moscovium

Moscovium (115Mc) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no known stable isotopes. The first isotope to be synthesized was 288Mc in 2004. There are five known radioisotopes from 286Mc to 290Mc. The longest-lived isotope is 290Mc with a half-life of 0.65 seconds.

Isotopes of moscovium (115Mc)
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
286Mc synth 20 ms[1] α 282Nh
287Mc synth 38 ms α 283Nh
288Mc synth 193 ms α 284Nh
289Mc synth 250 ms[2][3] α 285Nh
290Mc synth 650 ms[2][3] α 286Nh

List of isotopes

The isotopes undergo alpha decay into the corresponding isotope of nihonium, with half-lives increasing as neutron numbers increase.

Nuclide
 Z N Isotopic mass (Da)
[n 1][n 2]		 Half-life
 Decay
mode
 Daughter
isotope
 Spin and
parity
286Mc[4] 115 171 20+98
−9 ms		 α 282Nh
287Mc 115 172 287.19070(52)# 38+22
−10 ms[4]		 α 283Nh
288Mc 115 173 288.19274(62)# 193+15
−13 ms[4]		 α 284Nh
289Mc 115 174 289.19363(89)# 250+51
−35 ms[4]		 α 285Nh
290Mc[n 3] 115 175 290.19598(73)# 650+490
−200 ms		 α 286Nh
This table header & footer:
  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. Not directly synthesized, created as decay product of 294Ts

Nucleosynthesis
Chronology of isotope discovery
IsotopeYear discoveredDiscovery reaction
286Mc2021243Am(48Ca,5n)
287Mc2003243Am(48Ca,4n)
288Mc2003243Am(48Ca,3n)
289Mc2009249Bk(48Ca,4n)[2]
290Mc2009249Bk(48Ca,3n)[2]

Target-projectile combinations

The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z = 115. Each entry is a combination for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

TargetProjectileCNAttempt result
208Pb 75As283McReaction yet to be attempted
209Bi 76Ge285McReaction yet to be attempted
238U 51V289McFailure to date
243Am 48Ca291Mc[5][6]Successful reaction
241Am 48Ca289McPlanned reaction
243Am 44Ca287McReaction yet to be attempted

Hot fusion

Hot fusion reactions are processes that 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.

238U(51V,xn)289−xMc

There are strong indications that this reaction was performed in late 2004 as part of a uranium(IV) fluoride target test at the GSI. No reports have been published suggesting that no product atoms were detected, as anticipated by the team.[7]

243Am(48Ca,xn)291−xMc (x=2,3,4,5)

This reaction was first performed by the team in Dubna in July–August 2003. In two separate runs they were able to detect 3 atoms of 288Mc and a single atom of 287Mc. The reaction was studied further in June 2004 in an attempt to isolate the descendant 268Db from the 288Mc decay chain. After chemical separation of a +4/+5 fraction, 15 SF decays were measured with a lifetime consistent with 268Db. In order to prove that the decays were from dubnium-268, the team repeated the reaction in August 2005 and separated the +4 and +5 fractions and further separated the +5 fractions into tantalum-like and niobium-like ones. Five SF activities were observed, all occurring in the niobium-like fractions and none in the tantalum-like fractions, proving that the product was indeed isotopes of dubnium.

In a series of experiments between October 2010 – February 2011, scientists at the FLNR studied this reaction at a range of excitation energies. They were able to detect 21 atoms of 288Mc and one atom of 289Mc, from the 2n exit channel. This latter result was used to support the synthesis of tennessine. The 3n excitation function was completed with a maximum at ~8 pb. The data was consistent with that found in the first experiments in 2003.

This reaction was run again at five different energies in 2021 to test the new gas-filled separator at Dubna's SHE-factory. They detected 6 chains of 289Mc, 58 chains of 288Mc, and 2 chains of 287Mc. For the first time the 5n channel was observed with 2 atoms of 286Mc.[8]

Reaction yields

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

ProjectileTargetCN2n3n4n5n
48Ca243Am291Mc3.7 pb, 39.0 MeV0.9 pb, 44.4 MeV

Decay characteristics

Theoretical calculations using a quantum-tunneling model support the experimental alpha-decay half-lives.[9]

Evaporation residue cross sections

The table below contains various target-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.

MD = multi-dimensional; DNS = Di-nuclear system; σ = cross section

TargetProjectileCNChannel (product)σmaxModelRef
243Am 48Ca291Mc3n (288Mc)3 pbMD[5]
243Am 48Ca291Mc4n (287Mc)2 pbMD[5]
243Am 48Ca291Mc3n (288Mc)1 pbDNS[6]
242Am 48Ca290Mc3n (287Mc)2.5 pbDNS[6]
241Am 48Ca289Mc4n (285Mc)1.04 pbDNS[10]

References
  1. Kovrizhnykh, N. (27 January 2022). "Update on the experiments at the SHE Factory". Flerov Laboratory of Nuclear Reactions. Retrieved 28 February 2022.
  2. Oganessian, Yuri Ts.; Abdullin, F. Sh.; Bailey, P. D.; et al. (2010-04-09). "Synthesis of a New Element with Atomic Number Z=117". Physical Review Letters. American Physical Society. 104 (142502): 142502. Bibcode:2010PhRvL.104n2502O. doi:10.1103/PhysRevLett.104.142502. PMID 20481935.
  3. Oganessian, Y.T. (2015). "Super-heavy element research". Reports on Progress in Physics. 78 (3): 036301. Bibcode:2015RPPh...78c6301O. doi:10.1088/0034-4885/78/3/036301. PMID 25746203. S2CID 37779526.
  4. Oganessian, Yu. Ts.; Utyonkov, V. K.; Kovrizhnykh, N. D.; et al. (2022). "New isotope 286Mc produced in the 243Am+48Ca reaction". Physical Review C. 106 (64306). Bibcode:2022PhRvC.106f4306O. doi:10.1103/PhysRevC.106.064306. S2CID 254435744.
  5. Zagrebaev, V. (2004). "Fusion-fission dynamics of super-heavy element formation and decay" (PDF). Nuclear Physics A. 734: 164–167. Bibcode:2004NuPhA.734..164Z. doi:10.1016/j.nuclphysa.2004.01.025.
  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. S2CID 18647291.
  7. "List of experiments 2000–2006". Univerzita Komenského v Bratislave. Archived from the original on July 23, 2007.
  8. "Both neutron properties and new results at SHE Factory".
  9. C. Samanta; P. Roy Chowdhury; D. N. Basu (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nucl. Phys. A. 789 (1–4): 142–154. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. doi:10.1016/j.nuclphysa.2007.04.001. S2CID 7496348.
  10. Zhu, L.; Su, J.; Zhang, F. (2016). "Influence of the neutron numbers of projectile and target on the evaporation residue cross sections in hot fusion reactions". Physical Review C. 93 (6): 064610. Bibcode:2016PhRvC..93f4610Z. doi:10.1103/PhysRevC.93.064610.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.