Physics:Isotopes of moscovium

Short description: Nuclides with atomic number of 115 but with different mass numbers

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.

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 (u)	Half-life	Decay mode	Daughter isotope	Spin and parity
286Mc	115	171		20+98 −9 ms	α	282Nh
287Mc	115	172	287.19082(48)#	38+22 −10 ms	α	283Nh
288Mc	115	173	288.19288(58)#	193+15 −13 ms	α	284Nh
289Mc	115	174	289.19397(83)#	250+51 −35 ms	α	285Nh
290Mc	115	175	290.19624(64)#	650+490 −200 ms	α	286Nh

Nucleosynthesis

Chronology of isotope discovery

Isotope	Year discovered	Discovery reaction
286Mc	2021	243Am(48Ca,5n)
287Mc	2003	243Am(48Ca,4n)
288Mc	2003	243Am(48Ca,3n)
289Mc	2009	249Bk(48Ca,4n)
290Mc	2009	249Bk(48Ca,3n)

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.

Target	Projectile	CN	Attempt result
208Pb	75As	283Mc	Reaction yet to be attempted
209Bi	76Ge	285Mc	Reaction yet to be attempted
238U	51V	289Mc	Failure to date
243Am	48Ca	291Mc	Successful reaction
241Am	48Ca	289Mc	Planned reaction
243Am	44Ca	287Mc	Reaction 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.

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.

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.

Projectile	Target	CN	2n	3n	4n	5n
48Ca	243Am	291Mc		3.7 pb, 39.0 MeV	0.9 pb, 44.4 MeV

Theoretical calculations

Decay characteristics

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

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

Target	Projectile	CN	Channel (product)	σmax	Model	Ref
243Am	48Ca	291Mc	3n (288Mc)	3 pb	MD
243Am	48Ca	291Mc	4n (287Mc)	2 pb	MD
243Am	48Ca	291Mc	3n (288Mc)	1 pb	DNS
242Am	48Ca	290Mc	3n (287Mc)	2.5 pb	DNS
241Am	48Ca	289Mc	4n (285Mc)	1.04 pb	DNS

References

• Isotopic compositions and standard atomic masses from:
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. 
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A 729: 3–128, doi:10.1016/j.nuclphysa.2003.11.001, Bibcode: 2003NuPhA.729....3A, https://hal.archives-ouvertes.fr/in2p3-00020241/document 
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. 
  • Lide, David R., ed (2004). "11. Table of the Isotopes". CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.