Isotopes of roentgenium

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Main isotopes of roentgenium
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
286Rg[1] syn 640 s? α 282Mt
282Rg[2] syn 2 min α 278Mt
281Rg[3][4] syn 17 s SF (90%)
α (10%) 277Mt
280Rg syn 4 s α 276Mt
279Rg syn 0.1 s α 275Mt

Roentgenium (111Rg) is a synthetic element, and thus a standard atomic weight 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, although the unconfirmed 286Rg may have a longer half-life of about 11 minutes.

List of isotopes[edit]

Z(p) N(n)  
isotopic mass (u)
half-life decay
mode(s)[n 1]
272Rg 111 161 272.15327(25)# 2.0(8) ms
[3.8(+14−8) ms]
α 268Mt 5+#,6+#
273Rg 111 162 273.15313(57)# 5# ms
274Rg[n 2] 111 163 274.15525(19)# 6.4(+307−29) ms α 270Mt
275Rg 111 164 275.15594(56)# 10# ms
276Rg 111 165 276.15833(68)# 100# ms
277Rg 111 166 277.15907(61)# 1# s
278Rg[n 3] 111 167 278.16149(38)# 4.2(+75−17) ms α 274Mt
279Rg[n 4] 111 168 279.16272(51)# 0.17(+81−8) s α 275Mt
280Rg[n 5] 111 169 280.16514(61)# 3.6(+43−13) s α (87%) 276Mt
EC (13%)[5] 280Ds
281Rg[n 6] 111 170 281.16636(89)# 17 (+6−3) s[4] SF (90%) (various)
α (10%) 277Mt[4]
282Rg[n 7] 111 171 282.16912(72)# 2.1 (+1.4-0.6) min[6] α 278Mt
283Rg 111 172 283.17054(79)# 10# min
286Rg[n 8] 111 175 640 s? α 282Mt
  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
  8. ^ Not directly synthesised, occurs in decay chain of 290Fl and 294Lv; unconfirmed


  • 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[edit]


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.[7]

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.[8] 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.[7] The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).[9]

Cold fusion[edit]

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.[10] A further 3 atoms were synthesized in 2002.[11] The discovery of roentgenium was confirmed in 2003 when a team at RIKEN measured the decays of 14 atoms of 272Rg.[12]

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

+ 65

This reaction was conducted as part of their study of projectiles with odd atomic number in cold fusion reactions.[13]

The 205Tl(70Zn,n)274Rg reaction was tried by the RIKEN team in 2004 and repeated in 2010 in an attempt to secure the discovery of its parent 278Nh:[14]

+ 70

Due to the weakness of the thallium target, they were unable to detect any atoms of 274Rg.[14]

As decay product[edit]

List of roentgenium isotopes observed by decay
Evaporation residue Observed roentgenium isotope
294Lv, 290Fl, 290Nh ? 286Rg ?
294Ts, 290Mc, 286Nh 282Rg[15]
293Ts, 289Mc, 285Nh 281Rg[15]
288Mc, 284Nh 280Rg[16]
287Mc, 283Nh 279Rg[16]
282Nh 278Rg[16]
278Nh 274Rg[17]

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 seven known isotopes; all of them undergo alpha decays to become roentgenium nuclei, with mass numbers between 274 and 286. Parent nihonium nuclei can be themselves decay products of flerovium, moscovium, livermorium, or tennessine. To date, no other elements have been known to decay to roentgenium.[18] 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:[15]

+ 4
+ 4
+ 4

Nuclear isomerism[edit]


Two atoms of 274Rg have been observed in the decay chain of 278Nh. 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.[17]


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.[10][12]

Chemical yields of isotopes[edit]

Cold fusion[edit]

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.

Projectile Target CN 1n 2n 3n
64Ni 209Bi 273Rg 3.5 pb, 12.5 MeV
65Cu 208Pb 273Rg 1.7 pb, 13.2 MeV


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  2. ^ Khuyagbaatar, J.; Yakushev, A.; Düllmann, Ch. E.; et al. (2014). "48Ca+249Bk Fusion Reaction Leading to Element Z=117: Long-Lived α-Decaying 270Db and Discovery of 266Lr". Physical Review Letters. 112 (17): 172501. doi:10.1103/PhysRevLett.112.172501. PMID 24836239. 
  3. ^ Oganessian, Yuri Ts.; Abdullin, F. Sh.; Alexander, C.; et al. (2013-05-30). "Experimental studies of the 249Bk + 48Ca reaction including decay properties and excitation function for isotopes of element 117, and discovery of the new isotope 277Mt". Physical Review C. American Physical Society. 87 (054621). Bibcode:2013PhRvC..87e4621O. doi:10.1103/PhysRevC.87.054621. 
  4. ^ a b c Oganessian, Yu. Ts.; et al. (2013). "Experimental studies of the 249Bk + 48Ca reaction including decay properties and excitation function for isotopes of element 117, and discovery of the new isotope 277Mt". Physical Review C. 87 (5): 054621. Bibcode:2013PhRvC..87e4621O. doi:10.1103/PhysRevC.87.054621. 
  5. ^
  6. ^ Khuyagbaatar, J.; Yakushev, A.; Düllmann, Ch. E.; et al. (2014). "48Ca+249Bk Fusion Reaction Leading to Element Z=117: Long-Lived α-Decaying 270Db and Discovery of 266Lr". Physical Review Letters. 112 (17): 172501. Bibcode:2014PhRvL.112q2501K. doi:10.1103/PhysRevLett.112.172501. PMID 24836239. 
  7. ^ a b Armbruster, Peter & Munzenberg, Gottfried (1989). "Creating superheavy elements". Scientific American. 34: 36–42. 
  8. ^ Barber, Robert C.; Gäggeler, Heinz W.; Karol, Paul J.; Nakahara, Hiromichi; Vardaci, Emanuele; Vogt, Erich (2009). "Discovery of the element with atomic number 112 (IUPAC Technical Report)". Pure and Applied Chemistry. 81 (7): 1331. doi:10.1351/PAC-REP-08-03-05. 
  9. ^ Fleischmann, Martin; Pons, Stanley (1989). "Electrochemically induced nuclear fusion of deuterium". Journal of Electroanalytical Chemistry and Interfacial Electrochemistry. Elsevier. 261 (2): 301–308. doi:10.1016/0022-0728(89)80006-3. Retrieved 15 October 2012. 
  10. ^ a b Hofmann, S.; Ninov, V.; Heßberger, F. P.; Armbruster, P.; Folger, H.; Münzenberg, G.; Schött, H. J.; Popeko, A. G.; et al. (1995). "The new element 111". Zeitschrift für Physik A. 350 (4): 281–282. Bibcode:1995ZPhyA.350..281H. doi:10.1007/BF01291182. 
  11. ^ Hofmann, S.; Heßberger, F. P.; Ackermann, D.; Münzenberg, G.; Antalic, S.; Cagarda, P.; Kindler, B.; Kojouharova, J.; et al. (2002). "New results on elements 111 and 112". The European Physical Journal A. 14 (2): 147–157. doi:10.1140/epja/i2001-10119-x. 
  12. ^ a b Morita, K.; Morimoto, K. K.; Kaji, D.; Goto, S.; Haba, H.; Ideguchi, E.; Kanungo, R.; Katori, K.; Koura, H.; Kudo, H.; Ohnishi, T.; Ozawa, A.; Peter, J. C.; Suda, T.; Sueki, K.; Tanihata, I.; Tokanai, F.; Xu, H.; Yeremin, A. V.; Yoneda, A.; Yoshida, A.; Zhao, Y.-L.; Zheng, T. (2004). "Status of heavy element research using GARIS at RIKEN". Nuclear Physics A. 734: 101–108. Bibcode:2004NuPhA.734..101M. doi:10.1016/j.nuclphysa.2004.01.019. 
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  17. ^ a b Morita, Kosuke; Morimoto, Kouji; Kaji, Daiya; Akiyama, Takahiro; Goto, Sin-ichi; Haba, Hiromitsu; Ideguchi, Eiji; Kanungo, Rituparna; Katori, Kenji; Koura, Hiroyuki; Kudo, Hisaaki; Ohnishi, Tetsuya; Ozawa, Akira; Suda, Toshimi; Sueki, Keisuke; Xu, HuShan; Yamaguchi, Takayuki; Yoneda, Akira; Yoshida, Atsushi; Zhao, YuLiang (2004). "Experiment on the Synthesis of Element 113 in the Reaction 209Bi(70Zn,n)278113". Journal of the Physical Society of Japan. 73 (10): 2593–2596. Bibcode:2004JPSJ...73.2593M. doi:10.1143/JPSJ.73.2593. 
  18. ^ Sonzogni, Alejandro. "Interactive Chart of Nuclides". National Nuclear Data Center: Brookhaven National Laboratory. Retrieved 2008-06-06. 

Isotopes of darmstadtium Isotopes of roentgenium Isotopes of copernicium
Table of nuclides