Isotopes of meitnerium

Meitnerium (Mt) is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was ²⁶⁶Mt in 1982 (this is also the only isotope directly synthesized, all other isotopes are decay products of heavier elements). There are eight known isotopes, from ²⁶⁶Mt to ²⁷⁸Mt. There may also be two isomers. The longest-lived of the known isotopes is ²⁷⁸Mt with a half-life of 8 seconds.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin
	excitation energy
266Mt	109	157	266.13737(33)#	1.2(4) ms	α	262Bh
268Mt[n 1]	109	159	268.13865(25)#	21(+8-5) ms	α	264Bh	5+#,6+#
268mMt[n 2]	0+X keV			0.07(+10-3) s	α	264Bh
270Mt[n 3]	109	161	270.14033(18)#	0.57 s	α	266Bh
270mMt[n 2]				1.1 s?	α	266Bh
274Mt[n 4]	109	165	274.14725(38)#	0.45 s	α	270Bh
275Mt[n 5]	109	166	275.14882(50)#	9.7(+460-44) ms	α	271Bh
276Mt[n 6]	109	167	276.15159(59)#	0.72(+87-25) s	α	272Bh
277Mt[n 7]	109	168	277.15327(82)#	~5 ms[1][2]	SF	(various)
278Mt[n 8]	109	169	278.15631(68)#	7.6 s[3]	α	274Bh

1. ↑ Not directly synthesized, occurs as decay product of ²⁷²Rg
2. ↑ 2.0 2.1 This isomer is unconfirmed
3. ↑ Not directly synthesized, occurs in decay chain of ²⁷⁸Uut
4. ↑ Not directly synthesized, occurs in decay chain of ²⁸²Uut
5. ↑ Not directly synthesized, occurs in decay chain of ²⁸⁷Uup
6. ↑ Not directly synthesized, occurs in decay chain of ²⁸⁸Uup
7. ↑ Not directly synthesized, occurs in decay chain of ²⁹³Uus
8. ↑ Not directly synthesized, occurs in decay chain of ²⁹⁴Uus

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 meitnerium are produced by bombarding lighter elements in particle accelerators that induce fusion reactions. Whereas the lightest isotope of meitnerium, meitnerium-266, can be synthesized directly this way, all the heavier meitnerium isotopes 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] Nevertheless, the products of hot fusion tend to still have more neutrons overall. 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

After the first successful synthesis of meitnerium in 1982 by the GSI team,^[7] a team at the Joint Institute for Nuclear Research in Dubna, Russia, also tried to observe the new element by bombarding bismuth-209 with iron-58. In 1985 they managed to identity alpha decays from the descendant isotope ²⁴⁶Cf indicating the formation of meitnerium. The observation of a further two atoms of ²⁶⁶Mt from the same reaction was reported in 1988 and of another 12 in 1997 by the German team at GSI.^[8][9]

The same meitnerium isotope was also observed by the Russian team at Dubna in 1985 from the reaction:

208
82Pb + 59
27Co → 266
109Mt + n

by detecting the alpha decay of the descendant ²⁴⁶Cf nuclei. In 2007, an American team at the Lawrence Berkeley National Laboratory (LBNL) confirmed the decay chain of the ²⁶⁶Mt isotope from this reaction.^[10]

Hot fusion

In 2002–2003, the team at the LBNL attempted to generate the isotope ²⁷¹Mt to study its chemical properties by bombarding uranium-238 with chlorine-37, but without success.^[11] Another possible reaction that would form this isotope would be the fusion of berkelium-249 with magnesium-26; however, the yield for this reaction is expected to be very low due to the high radioactivity of the berkelium-249 target.^[12] Other long-lived isotopes were unsuccessfully targeted by a team at Lawrence Livermore National Laboratory (LLNL) in 1988 by bombarding einsteinium-254 with neon-22.^[11]

Decay products

All the isotopes of meitnerium except meitnerium-266 have been detected only in the decay chains of elements with a higher atomic number, such as roentgenium. Roentgenium currently has seven known isotopes; all but one of them undergo alpha decays to become meitnerium nuclei, with mass numbers between 268 and 278. Parent roentgenium nuclei can be themselves decay products of ununtrium, ununpentium, or ununseptium. To date, no other elements have been known to decay to meitnerium.^[18] For example, in January 2010, the Dubna team (JINR) identified meitnerium-278 as a product in the decay of ununseptium via an alpha decay sequence:^[13]

294
117Uus → 290
115Uup + 4
2He

290
115Uup → 286
113Uut + 4
2He

286
113Uut → 282
111Rg + 4
2He

282
111Rg → 278
109Mt + 4
2He

Nuclear isomerism

²⁷⁰Mt

Two atoms of ²⁷⁰Mt have been identified in the decay chains of ²⁷⁸Uut. The two decays have very different lifetimes and decay energies and are also produced from two apparently different isomers of ²⁷⁴Rg. The first isomer decays by emission of an alpha particle with energy 10.03 MeV and has a lifetime of 7.16 ms. The other alpha decays with a lifetime of 1.63 s; the decay energy was not measured. An assignment to specific levels is not possible with the limited data available and further research is required.^[16]

²⁶⁸Mt

The alpha decay spectrum for ²⁶⁸Mt appears to be complicated from the results of several experiments. Alpha particles of energies 10.28, 10.22 and 10.10 MeV have been observed, emitted from ²⁶⁸Mt atoms with half-lives of 42 ms, 21 ms and 102 ms respectively. The long-lived decay must be assigned to an isomeric level. The discrepancy between the other two half-lives has yet to be resolved. An assignment to specific levels is not possible with the data available and further research is required.^[17]

Nuclear isomerism

²⁷⁰Mt

Two atoms of ²⁷⁰Mt have been identified in the decay chains of ²⁷⁸Uut. The two decays have very different lifetimes and decay energies and are also produced from two apparently different isomers in ²⁷⁴Rg. The first isomer decays by emission of an 10.03 MeV alpha particle with a lifetime 7.2 ms. The other decays by emitting an alpha particle with a lifetime of 1.63 s. An assignment to specific levels is not possible with the limited data available. Further research is required.

²⁶⁸Mt

The alpha decay spectrum for ²⁶⁸Mt appears to be complicated from the results of several experiments. Alpha lines of 10.28,10.22 and 10.10 MeV have been observed. Half-lives of 42 ms, 21 ms and 102 ms have been determined. The long-lived decay is associated with alpha particles of energy 10.10 MeV and must be assigned to an isomeric level. The discrepancy between the other two half-lives has yet to be resolved. An assignment to specific levels is not possible with the data available and further research is required.

Chemical yields of isotopes

Cold fusion

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

Projectile	Target	CN	1n	2n	3n
58Fe	209Bi	267Mt	7.5 pb
59Co	208Pb	267Mt	2.6 pb, 14.9 MeV

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.

HIVAP = heavy-ion vaporisation statistical-evaporation model; σ = cross section

Target	Projectile	CN	Channel (product)	σmax	Model	Ref
243Am	30Si	273Mt	3n (270Mt)	22 pb	HIVAP	[19]
243Am	28Si	271Mt	4n (267Mt)	3 pb	HIVAP	[19]
249Bk	26Mg	275Mt	4n (271Mt)	9.5 pb	HIVAP	[19]
254Es	22Ne	276Mt	4n (272Mt)	8 pb	HIVAP	[19]
254Es	20Ne	274Mt	4-5n (270,269Mt)	3 pb	HIVAP	[19]

References

• Isotope masses from:
  • M. Wang, G. Audi, A. H. Wapstra, F. G. Kondev, M. MacCormick, X. Xu and B. Pfeiffer (2012). "The AME2012 atomic mass evaluation (II). Tables, graphs and references". Chinese Physics C, 36 (12): 1603–2014. Bibcode:2012ChPhC..36....3M. doi:10.1088/1674-1137/36/12/003. 
  • G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. 
• Isotopic compositions and standard atomic masses from:
  • J. R. de Laeter, J. K. Böhlke, P. De Bièvre, H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683. 
  • M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary. 
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. 
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. 
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9. 
  • GSI (2011). "Superheavy Element Research at GSI". GSI. Retrieved February 2013. 

Isotopes of hassium	Isotopes of meitnerium	Isotopes of darmstadtium
Table of nuclides

Isotopes of the chemical elements
1 H																	2 He
3 Li	4 Be											5 B	6 C	7 N	8 O	9 F	10 Ne
11 Na	12 Mg											13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
19 K	20 Ca	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
37 Rb	38 Sr	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
55 Cs	56 Ba		72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
87 Fr	88 Ra		104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Uut	114 Fl	115 Uup	116 Lv	117 Uus	118 Uuo
		57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu
		89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr
Table of nuclides Categories: Isotopes Tables of nuclides Metastable isotopes Isotopes by element