Isotopes of roentgenium

Roentgenium (Rg) is a synthetic element, and thus a standard atomic mass cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was ²⁷²Rg in 1994, which is also the only directly synthesized isotope, all others are decay products of nihonium, moscovium, and tennessine. There are 7 known radioisotopes from ²⁷²Rg to ²⁸²Rg. The longest-lived isotope is ²⁸²Rg with a half-life of 2.1 minutes.

Table

1. ↑ Abbreviations:
   SF: Spontaneous fission
2. ↑ Not directly synthesized, occurs as a decay product of ²⁷⁸Nh
3. ↑ Not directly synthesized, occurs as a decay product of ²⁸²Nh
4. ↑ Not directly synthesized, occurs in decay chain of ²⁸⁷Mc
5. ↑ Not directly synthesized, occurs in decay chain of ²⁸⁸Mc
6. ↑ Not directly synthesized, occurs in decay chain of ²⁹³Ts
7. ↑ Not directly synthesized, occurs in decay chain of ²⁹⁴Ts

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 roentgenium are produced by bombarding lighter elements in particle accelerators that induce fusion reactions. Whereas the lightest isotope of roentgenium, roentgenium-272, can be synthesized directly this way, all the heavier roentgenium isotopes have only been observed as decay products of elements with higher atomic numbers.^[4]

Depending on the energies involved, fusion reactions can be categorized as "hot" or "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 first successful synthesis of roentgenium in 1994 by the GSI team, a team at the Joint Institute for Nuclear Research in Dubna, Russia, also tried to synthesize roentgenium by bombarding bismuth-209 with nickel-64 in 1986. No roentgenium atoms were identified. After an upgrade of their facilities, the team at GSI successfully detected 3 atoms of ²⁷²Rg in their discovery experiment.^[7] A further 3 atoms were synthesized in 2002.^[8] The discovery of roentgenium was confirmed in 2003 when a team at RIKEN measured the decays of 14 atoms of ²⁷²Rg.^[9]

The same roentgenium isotope was also observed by an American team at the Lawrence Berkeley National Laboratory (LBNL) from the reaction:

208
82Pb
+ 65
29Cu
→ 272
111Rg
+
n

This reaction was conducted as part of their study of projectiles with odd atomic number in cold fusion reactions.^[10]

As decay product

All the isotopes of roentgenium except roentgenium-272 have been detected only in the decay chains of elements with a higher atomic number, such as nihonium. Nihonium currently has six known isotopes; all of them undergo alpha decays to become roentgenium nuclei, with mass numbers between 274 and 282. Parent nihonium nuclei can be themselves decay products of moscovium or tennessine. To date, no other elements have been known to decay to roentgenium.^[14] For example, in January 2010, the Dubna team (JINR) identified roentgenium-281 as a final product in the decay of tennessine via an alpha decay sequence:^[11]

293
117Ts
→ 289
115Mc
+ 4
2He

289
115Mc
→ 285
113Nh
+ 4
2He

285
113Nh
→ 281
111Rg
+ 4
2He

Nuclear isomerism

²⁷⁴Rg

Two atoms of ²⁷⁴Rg have been observed in the decay chain of ²⁷⁸Uut. They decay by alpha emission, emitting alpha particles with different energies, and have different lifetimes. In addition, the two entire decay chains appear to be different. This suggests the presence of two nuclear isomers but further research is required.^[13]

²⁷²Rg

Four alpha particles emitted from ²⁷²Rg with energies of 11.37, 11.03, 10.82, and 10.40 MeV have been detected. The GSI measured ²⁷²Rg to have a half-life of 1.6 ms while recent data from RIKEN have given a half-life of 3.8 ms. The conflicting data may be due to nuclear isomers but the current data are insufficient to come to any firm assignments.^[7][9]

Chemical yields of isotopes

Cold fusion

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

References

• Isotope masses from:
  • M. Wang; G. Audi; A. H. Wapstra; F. G. Kondev; M. MacCormick; X. Xu; et al. (2012). "The AME2012 atomic mass evaluation (II). Tables, graphs and references." (PDF). 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; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). 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; 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; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). 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.  Check date values in: |access-date= (help)
  • 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. 
  • Yu. Ts. Oganessian (2007). "Heaviest nuclei from ⁴⁸Ca-induced reactions". Journal of Physics G. 34 (4): R165–R242. Bibcode:2007JPhG...34..165O. doi:10.1088/0954-3899/34/4/R01. 

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 Nh	114 Fl	115 Mc	116 Lv	117 Ts	118 Og
		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