Physics:Isotopes of hassium

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Short description: Nuclides with atomic number of 108 but with different mass numbers

Hassium (108Hs) 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 265Hs in 1984. There are 13 known isotopes from 263Hs to 277Hs and 1–4 isomers. The most stable isotope of hassium cannot be determined based on existing data due to uncertainty that arises from the low number of measurements. The half-lives of 269Hs and 271Hs are about 12 seconds, whereas that of 270Hs is about 7.6 seconds. It is also possible that 277mHs is more stable than these, with its half-life likely being 130±100 seconds, but only one event of decay of this isotope has been registered as of 2016.[1][2]

List of isotopes

Nuclide
[n 1] 		Z N Isotopic mass (u)
[n 2][n 3] 		Half-life
 Decay
mode
[n 4] 		Daughter
isotope
 Spin and
parity
[n 5]
Excitation energy
263Hs 108 155 263.12848(21)# 760(40) µs α 259Sg 3/2+#
264Hs[3] 108 156 264.12836(3) 0.7(3) ms α (70%) 260Sg 0+
SF (30%) (various)
265Hs[4] 108 157 265.129792(26) 1.96(16) ms α 261Sg 9/2+#
265mHs 229(22) keV 360(150) µs α 261Sg 3/2+#
266Hs[n 6][5] 108 158 266.130049(29) 2.97+0.78
−0.51 ms 		α (76%) 262Sg 0+
SF (24%) (various)
266mHs 1100(70) keV 280(220) ms
[74+354
−34 ms] 		α 262Sg 9-#
267Hs 108 159 267.13168(10)# 55(11) ms α 263Sg 5/2+#
267mHs[n 7] 39(24) keV 990(90) µs α 263Sg
268Hs 108 160 268.13201(32)# 1.42(1.13) s
[0.38+1.8
−0.17 s] 		α 264Sg 0+
269Hs 108 161 269.13365(14)# 12+9
−4 s[6] 		α 265Sg 9/2+#
270Hs[7] 108 162 270.13431(27)# 7.6+4.9
−2.2 s 		α 266Sg 0+
SF (<50%) (various)
271Hs 108 163 271.13708(30)# ~12 s[8] α 267Sg
272Hs[n 8][9] 108 164 272.13849(55)# 160+190
−60 ms 		α 268Sg 0+
273Hs[n 9] 108 165 273.14146(40)# 510+300
−140 ms[10] 		α 269Sg 3/2+#
275Hs[n 10][11] 108 167 275.14653(64)# 600+230
−130 ms 		α 271Sg
SF (<11%) (various)
277Hs[n 11] 108 169 277.15177(48)# 18+25
−7 ms[12] 		SF (various) 3/2+#
277mHs[n 7][n 11][13] 100(100) keV# 130(100) s SF (various)
278Hs[n 12][n 13] 108 170 278.15375(32)# 2# s SF (various) 0+
  1. ↑ mHs – Excited nuclear isomer.
  2. ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. ↑ Modes of decay:
    SF: Spontaneous fission
  5. ↑ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  6. ↑ Not directly synthesized, occurs as decay product of 270Ds
  7. ↑ 7.0 7.1 Existence of this isomer is unconfirmed
  8. ↑ Not directly synthesized, occurs in decay chain of 276Ds
  9. ↑ Not directly synthesized, occurs in decay chain of 285Fl
  10. ↑ Not directly synthesized, occurs in decay chain of 287Fl
  11. ↑ 11.0 11.1 Not directly synthesized, occurs in decay chain of 289Fl
  12. ↑ Not directly synthesized, created as decay product of 290Fl
  13. ↑ This isotope is unconfirmed

Isotopes and nuclear properties

Target-projectile combinations leading to Z=108 compound nuclei

Target Projectile CN Attempt result
136Xe 136Xe 272Hs Failure to date
198Pt 70Zn 268Hs Failure to date[14]
208Pb 58Fe 266Hs Successful reaction
207Pb 58Fe 265Hs Successful reaction
208Pb 56Fe 264Hs Successful reaction
207Pb 56Fe 263Hs Reaction yet to be attempted
206Pb 58Fe 264Hs Successful reaction
209Bi 55Mn 264Hs Failure to date
226Ra 48Ca 274Hs Successful reaction
232Th 40Ar 272Hs Reaction yet to be attempted
238U 36S 274Hs Successful reaction
238U 34S 272Hs Successful reaction
244Pu 30Si 274Hs Reaction yet to be attempted
248Cm 26Mg 274Hs Successful reaction
248Cm 25Mg 273Hs Failure to date
250Cm 26Mg 276Hs Reaction yet to be attempted
249Cf 22Ne 271Hs Successful reaction

Nucleosynthesis

Superheavy elements such as hassium are produced by bombarding lighter elements in particle accelerators that induce fusion reactions. Whereas most of the isotopes of hassium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers.[15]

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.[16] 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.[15] The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).[17]

Cold fusion

Before the first successful synthesis of hassium in 1984 by the GSI team, scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia also tried to synthesize hassium by bombarding lead-208 with iron-58 in 1978. No hassium atoms were identified. They repeated the experiment in 1984 and were able to detect a spontaneous fission activity assigned to 260Sg, the daughter of 264Hs.[18] Later that year, they tried the experiment again, and tried to chemically identify the decay products of hassium to provide support to their synthesis of element 108. They were able to detect several alpha decays of 253Es and 253Fm, decay products of 265Hs.[19]

In the official discovery of the element in 1984, the team at GSI studied the same reaction using the alpha decay genetic correlation method and were able to positively identify 3 atoms of 265Hs.[20] After an upgrade of their facilities in 1993, the team repeated the experiment in 1994 and detected 75 atoms of 265Hs and 2 atoms of 264Hs, during the measurement of a partial excitation function for the 1n neutron evaporation channel.[21] A further run of the reaction was conducted in late 1997 in which a further 20 atoms were detected.[22] This discovery experiment was successfully repeated in 2002 at RIKEN (10 atoms) and in 2003 at GANIL (7 atoms). The team at RIKEN further studied the reaction in 2008 in order to conduct the first spectroscopic studies of the even-even nucleus 264Hs. They were also able to detect a further 29 atoms of 265Hs.

The team at Dubna also conducted the analogous reaction with a lead-207 target instead of a lead-208 target in 1984:

20782Pb + 5826Fe → 264108Hs + neutron

They were able to detect the same spontaneous fission activity as observed in the reaction with a lead-208 target and once again assigned it to 260Sg, daughter of 264Hs.[19] The team at GSI first studied the reaction in 1986 using the method of genetic correlation of alpha decays and identified a single atom of 264Hs with a cross section of 3.2 pb.[23] The reaction was repeated in 1994 and the team were able to measure both alpha decay and spontaneous fission for 264Hs. This reaction was also studied in 2008 at RIKEN in order to conduct the first spectroscopic studies of the even-even nucleus 264Hs. The team detected 11 atoms of 264Hs.

In 2008, the team at RIKEN conducted the analogous reaction with a lead-206 target for the first time:

20682Pb + 5826Fe → 263108Hs + neutron

They were able to identify 8 atoms of the new isotope 263Hs.[24]

In 2008, the team at the Lawrence Berkeley National Laboratory (LBNL) studied the analogous reaction with iron-56 projectiles for the first time:

20882Pb + 5626Fe → 263108Hs + neutron

They were able to produce and identify six atoms of the new isotope 263Hs.[25] A few months later, the RIKEN team also published their results on the same reaction.[26]

Further attempts to synthesise nuclei of hassium were performed the team at Dubna in 1983 using the cold fusion reaction between a bismuth-209 target and manganese-55 projectiles:

20983Bi + 5525Mn → 264−x108Hs + x Neutron (x = 1 or 2)

They were able to detect a spontaneous fission activity assigned to 255Rf, a product of the 263Hs decay chain. Identical results were measured in a repeat run in 1984.[19] In a subsequent experiment in 1983, they applied the method of chemical identification of a descendant to provide support to the synthesis of hassium. They were able to detect alpha decays from fermium isotopes, assigned as descendants of the decay of 262Hs. This reaction has not been tried since and 262Hs is currently unconfirmed.[19]

Hot fusion

Under the leadership of Yuri Oganessian, the team at the Joint Institute for Nuclear Research studied the hot fusion reaction between calcium-48 projectiles and radium-226 targets in 1978:

22688Ra + 4820Ca → 270108Hs + 4 Neutron

However, results are not available in the literature.[19] The reaction was repeated at the JINR in June 2008 and 4 atoms of the isotope 270Hs were detected.[27] In January 2009, the team repeated the experiment and a further 2 atoms of 270Hs were detected.[28]

The team at Dubna studied the reaction between californium-249 targets and neon-22 projectiles in 1983 by detecting spontaneous fission activities:

24998Cf + 2210Ne → 271−x108Hs + x Neutron

Several short spontaneous fission activities were found, indicating the formation of nuclei of hassium.[19]

The hot fusion reaction between uranium-238 targets and projectiles of the rare and expensive isotope sulfur-36 was conducted at the GSI in April–May 2008:

23892U + 3616S → 270108Hs + 4 Neutron

Preliminary results show that a single atom of 270Hs was detected. This experiment confirmed the decay properties of the isotopes 270Hs and 266Sg.[29]

In March 1994, the team at Dubna led by the late Yuri Lazarev attempted the analogous reaction with sulfur-34 projectiles:

23892U + 3416S → 272−x108Hs + x Neutron (x = 4 or 5)

They announced the detection of 3 atoms of 267Hs from the 5n neutron evaporation channel.[30] The decay properties were confirmed by the team at GSI in their simultaneous study of darmstadtium. The reaction was repeated at the GSI in January–February 2009 in order to search for the new isotope 268Hs. The team, led by Prof. Nishio, detected a single atom each of both 268Hs and 267Hs. The new isotope 268Hs underwent alpha decay to the previously known isotope 264Sg.

Between May 2001 and August 2005, a GSI–PSI (Paul Scherrer Institute) collaboration studied the nuclear reaction between curium-248 targets and magnesium-26 projectiles:

24896Cm + 2612Mg → 274−x108Hs + x Neutron (x = 3, 4, or 5)

The team studied the excitation function of the 3n, 4n, and 5n evaporation channels leading to the isotopes 269Hs, 270Hs, and 271Hs.[31][32] The synthesis of the doubly magic isotope 270Hs was published in December 2006 by the team of scientists from the Technical University of Munich.[33] It was reported that this isotope decayed by emission of an alpha particle with an energy of 8.83 MeV and a half-life of ~22 s. This figure has since been revised to 3.6 s.[34]

As decay product

List of hassium isotopes observed by decay
Evaporation residue Observed hassium isotope
267Ds 263Hs[35]
269Ds 265Hs[36]
270Ds 266Hs[37]
271Ds 267Hs[38]
277Cn, 273Ds 269Hs[39]
276Ds 272Hs[9]
285Fl, 281Cn, 277Ds 273Hs[40]
291Lv, 287Fl, 283Cn, 279Ds 275Hs[41]
293Lv, 289Fl, 285Cn, 281Ds 277Hs[42][43][44]

Hassium isotopes have been observed as decay products of darmstadtium. Darmstadtium currently has ten known isotopes, all but one of which have been shown to undergo alpha decays to become hassium nuclei with mass numbers between 263 and 277. Hassium isotopes with mass numbers 266, 272, 273, 275, and 277 to date have only been produced by decay of darmstadtium nuclei. Parent darmstadtium nuclei can be themselves decay products of copernicium, flerovium, or livermorium.[34] For example, in 2004, the Dubna team identified hassium-277 as a final product in the decay of livermorium-293 via an alpha decay sequence:[44]

293116Lv → 289114Fl + 42He
289114Fl → 285112Cn + 42He
285112Cn → 281110Ds + 42He
281110Ds → 277108Hs + 42He

Unconfirmed isotopes

List of hassium isotopes
Isotope Half-life[lower-alpha 1][lower-alpha 2] Decay
mode 		Discovery
year[46] 		Discovery
reaction[47][lower-alpha 3]
Value Ref
263Hs 760 760 μs [46] α, SF 2009 208Pb(56Fe,n)
264Hs 540 540 μs [46] α, SF 1986 207Pb(58Fe,n)
265Hs 1960 1.96 ms [46] α, SF 1984 208Pb(58Fe,n)
265mHs 360 360 μs [46] α 1995 208Pb(56Fe,n)
266Hs 3020 3.02 ms [46] α, SF 2001 270Ds(—,α)
266mHs 280000 280 ms [46] α 2011 270mDs(—,α)
267Hs 55000 55 ms [45] α 1995 238U(34S,5n)
267mHs 990 990 μs [45] α 2004 238U(34S,5n)
268Hs 1420000 1.42 s [45] α 2010 238U(34S,4n)
269Hs 16000000 16 s [45] α 1996 277Cn(—,2α)
270Hs 9000000 9 s [45] α 2003 248Cm(26Mg,4n)
271Hs 10000000 10 s

[lower-alpha 4]||[48]||α||2008||248Cm(26Mg,3n)

272Hs 160 ms [9] α 2022 276Ds(—,α)
273Hs 510000 510 ms [10] α 2010 285Fl(—,3α)
275Hs 600000 600 ms [11] α 2004 287Fl(—,3α)
277Hs 12000 12 ms [2] α 2010 289Fl(—,3α)
277mHs 130000000 130 s

[lower-alpha 5]||[2][49]||SF||2012||293mLv(—,4α)

277mHs

An isotope assigned to 277Hs has been observed on one occasion decaying by SF with a long half-life of ~11 minutes.[50] The isotope is not observed in the decay of the ground state of 281Ds but is observed in the decay from a rare, as yet unconfirmed isomeric level, namely 281mDs. The half-life is very long for the ground state and it is possible that it belongs to an isomeric level in 277Hs. It has also been suggested that this activity actually comes from 278Bh, formed as the great-great-granddaughter of 290Fl through one electron capture to 290Nh and three further alpha decays. Furthermore, in 2009, the team at the GSI observed a small alpha decay branch for 281Ds producing the nuclide 277Hs decaying by SF in a short lifetime. The measured half-life is close to the expected value for ground state isomer, 277Hs. Further research is required to confirm the production of the isomer.

Retracted isotopes

273Hs

In 1999, American scientists at the University of California, Berkeley, announced that they had succeeded in synthesizing three atoms of 293118.[51] These parent nuclei were reported to have successively emitted three alpha particles to form hassium-273 nuclei, which were claimed to have undergone an alpha decay, emitting alpha particles with decay energies of 9.78 and 9.47 MeV and half-life 1.2 s, but their claim was retracted in 2001.[52] The isotope, however, was produced in 2010 by the same team. The new data matched the previous (fabricated)[53] data.[40]

270Hs: prospects for a deformed doubly magic nucleus

According to macroscopic-microscopic (MM) theory, Z = 108 is a deformed proton magic number, in combination with the neutron shell at N = 162. This means that such nuclei are permanently deformed in their ground state but have high, narrow fission barriers to further deformation and hence relatively long SF partial half-lives. The SF half-lives in this region are typically reduced by a factor of 109 in comparison with those in the vicinity of the spherical doubly magic nucleus 298Fl, caused by an increase in the probability of barrier penetration by quantum tunnelling, due to the narrower fission barrier. In addition, N = 162 has been calculated as a deformed neutron magic number and hence the nucleus 270Hs has promise as a deformed doubly magic nucleus. Experimental data from the decay of Z = 110 isotopes 271Ds and 273Ds, provides strong evidence for the magic nature of the N = 162 sub-shell. The recent synthesis of 269Hs, 270Hs, and 271Hs also fully support the assignment of N = 162 as a magic closed shell. In particular, the low decay energy for 270Hs is in complete agreement with calculations.[54]

Evidence for the Z = 108 deformed proton shell

Evidence for the magicity of the Z = 108 proton shell can be deemed from two sources:

  1. the variation in the partial spontaneous fission half-lives for isotones
  2. the large gap in Qα for isotonic pairs between Z = 108 and Z = 110.

For SF, it is necessary to measure the half-lives for the isotonic nuclei 268Sg, 270Hs and 272Ds. Since fission of 270Hs has not been measured, detailed data of 268Sg fission is not yet available,[9] and 272Ds is still unknown, this method cannot be used to date to confirm the stabilizing nature of the Z = 108 shell. However, good evidence for the magicity of Z = 108 can be deemed from the large differences in the alpha decay energies measured for 270Hs, 271Ds and 273Ds. More conclusive evidence would come from the determination of the decay energy of the yet-unknown nuclide 272Ds.

Nuclear isomerism

277Hs

An isotope assigned to 277Hs has been observed on one occasion decaying by spontaneous fission with a long half-life of ~11 minutes.[55] The isotope is not observed in the decay of the most common isomer of 281Ds but is observed in the decay from a rare, as yet unconfirmed isomeric level, namely 281mDs. The half-life is very long for the ground state and it is possible that it belongs to an isomeric level in 277Hs. Furthermore, in 2009, the team at the GSI observed a small alpha decay branch for 281Ds producing an isotope of 277Hs decaying by spontaneous fission with a short lifetime. The measured half-life is close to the expected value for ground state isomer, 277Hs. Further research is required to confirm the production of the isomer.[42] A more recent study suggests that this observed activity may actually be from 278Bh.[56]

269Hs

The direct synthesis of 269Hs has resulted in the observation of three alpha particles with energies 9.21, 9.10, and 8.94 MeV emitted from 269Hs atoms. However, when this isotope is indirectly synthesized from the decay of 277Cn, only alpha particles with energy 9.21 MeV have been observed, indicating that this decay occurs from an isomeric level. Further research is required to confirm this.[31][39]

267Hs

267Hs is known to decay by alpha decay, emitting alpha particles with energies of 9.88, 9.83, and 9.75 MeV. It has a half-life of 52 ms. In the recent syntheses of 271Ds and 271mDs, additional activities have been observed. A 0.94 ms activity emitting alpha particles with energy 9.83 MeV has been observed in addition to longer lived ~0.8 s and ~6.0 s activities. Currently, none of these are assigned and confirmed and further research is required to positively identify them.[30]

265Hs

The synthesis of 265Hs has also provided evidence for two isomeric levels. The ground state decays by emission of an alpha particle with energy 10.30 MeV and has a half-life of 2.0 ms. The isomeric state has 300 keV of excess energy and decays by the emission of an alpha particle with energy 10.57 MeV and has a half-life of 0.75 ms.[20]

Future experiments

Scientists at the GSI are planning to search for isomers of 270Hs using the reaction 226Ra(48Ca,4n) in 2010 using the new TASCA facility at the GSI.[57] In addition, they also hope to study the spectroscopy of 269Hs, 265Sg and 261Rf, using the reaction 248Cm(26Mg,5n) or 226Ra(48Ca,5n). This will allow them to determine the level structure in 265Sg and 261Rf and attempt to give spin and parity assignments to the various proposed isomers.[58]

Physical production yields

The tables below provides cross-sections and excitation energies for nuclear reactions that produce isotopes of hassium directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.

Cold fusion

Projectile Target CN 1n 2n 3n
58Fe 208Pb 266Hs 69 pb, 13.9 MeV 4.5 pb
58Fe 207Pb 265Hs 3.2 pb

Hot fusion

Projectile Target CN 3n 4n 5n
48Ca 226Ra 274Hs 9.0 pb
36S 238U 274Hs 0.8 pb
34S 238U 272Hs 2.5 pb, 50.0 MeV
26Mg 248Cm 274Hs 2.5 pb 3.0 pb 7.0 pb

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.

DNS = Di-nuclear system ; σ = cross section

Target Projectile CN Channel (product) σ max Model Ref
136Xe 136Xe 272Hs 1–4n (271–268Hs) 10−6 pb DNS [59]
238U 34S 272Hs 4n (268Hs) 10 pb DNS [59]
238U 36S 274Hs 4n (270Hs) 42.97 pb DNS [60]
244Pu 30Si 274Hs 4n (270Hs) 185.1 pb DNS [60]
248Cm 26Mg 274Hs 4n (270Hs) 719.1 pb DNS [60]
250Cm 26Mg 276Hs 4n (272Hs) 185.2 pb DNS [60]

Notes

  1. ↑ Different sources give different values for half-lives; the most recently published values are listed. Uncertainties are not given.
  2. ↑ Few nuclei of each hassium isotope have been synthesized, and thus half-lives of these isotopes cannot be determined very precisely. Therefore, a half-life may be given as the most likely value alongside a confidence interval that corresponds to one standard deviation (such an interval based on future experiments, whose result is yet unknown, contains the true value with a probability of ~68.3%): for example, the value of 1.42 s in the isotope table obtained for 268Hs was listed in the source as 1.42 ±1.13 s, and this value is a modification of the value of 0.38+1.8−0.17 s.[45]
  3. ↑ The notation 208Pb(56Fe,n)263Hs denotes a nuclear reaction between a nucleus of 208Pb that was bombarded with a nucleus of 56Fe; the two fused, and after a single neutron had been emitted, the remaining nucleus was 263Hs. Another notation for this reaction would be 208Pb + 56Fe → 263Hs + n.
  4. ↑ Half-life of this isotope is estimated from trends across nuclides with the same number of protons and neutrons rather than measured directly.
  5. ↑ Only one event of decay of this isotope has been registered.

References

  1. ↑ "Radioactive Elements" (in en). 2018. https://ciaaw.org/radioactive-elements.htm. 
  2. ↑ 2.0 2.1 2.2 Audi et al. 2017, p. 030001-136.
  3. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *" (in English). Chinese Physics C, High Energy Physics and Nuclear Physics 45 (3): 030001. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. Bibcode: 2021ChPhC..45c0001K. 
  4. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *" (in English). Chinese Physics C, High Energy Physics and Nuclear Physics 45 (3): 030001. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. Bibcode: 2021ChPhC..45c0001K. 
  5. ↑ Ackermann, Dieter (23–27 January 2012). "270Ds and its decay products – K-isomers, α-sf competition and masses". Proceedings of 50th International Winter Meeting on Nuclear Physics — PoS(Bormio2012). 030. doi:10.22323/1.160.0030. https://pos.sissa.it/160/030/pdf. Retrieved 1 July 2023. 
  6. ↑ Sumita, Takayuki; Morimoto, Kouji; Kaji, Daiya; Haba, Hiromitsu; Ozeki, Kazutaka; Sakai, Ryutaro; Yoneda, Akira; Yoshida, Atsushi et al. (15 February 2013). "New Result on the Production of 277Cn by the 208Pb + 70Zn Reaction" (in en). Journal of the Physical Society of Japan 82 (2): 024202. doi:10.7566/JPSJ.82.024202. ISSN 0031-9015. Bibcode: 2013JPSJ...82b4202S. https://journals.jps.jp/doi/abs/10.7566/JPSJ.82.024202. Retrieved 1 July 2023. 
  7. ↑ Oganessian, Yu. Ts.; Utyonkov, V. K.; Abdullin, F. Sh.; Dmitriev, S. N.; Graeger, R.; Henderson, R. A.; Itkis, M. G.; Lobanov, Yu. V. et al. (5 March 2013). "Synthesis and study of decay properties of the doubly magic nucleus 270Hs in the 226Ra + 48Ca reaction". Physical Review C 87 (3): 034605. doi:10.1103/PhysRevC.87.034605. Bibcode: 2013PhRvC..87c4605O. 
  8. ↑ "New darmstadtium isotope discovered at Superheavy Element Factory". Joint Institute for Nuclear Research. 27 February 2023. http://www.jinr.ru/posts/new-darmstadtium-isotope-discovered-at-superheavy-element-factory/. 
  9. ↑ 9.0 9.1 9.2 9.3 Oganessian, Yu. Ts.Expression error: Unrecognized word "et". (2023). "New isotope 276Ds and its decay products 272Hs and 268Sg from the 232Th + 48Ca reaction". Physical Review C 108 (24611): 024611. doi:10.1103/PhysRevC.108.024611. Bibcode: 2023PhRvC.108b4611O. 
  10. ↑ 10.0 10.1 Utyonkov, V. K.; Brewer, N. T.; Oganessian, Yu. Ts.; Rykaczewski, K. P.; Abdullin, F. Sh.; Dimitriev, S. N.; Grzywacz, R. K.; Itkis, M. G. et al. (30 January 2018). "Neutron-deficient superheavy nuclei obtained in the 240Pu+48Ca reaction". Physical Review C 97 (14320): 014320. doi:10.1103/PhysRevC.97.014320. Bibcode: 2018PhRvC..97a4320U. 
  11. ↑ 11.0 11.1 Oganessian, Yu. Ts.Expression error: Unrecognized word "et". (2022). "Investigation of 48Ca-induced reactions with 242Pu and 238U targets at the JINR Superheavy Element Factory". Physical Review C 106 (24612): 024612. doi:10.1103/PhysRevC.106.024612. Bibcode: 2022PhRvC.106b4612O. 
  12. ↑ Cox, D. M.; Såmark-Roth, A.; Rudolph, D.; Sarmiento, L. G.; Clark, R. M.; Egido, J. L.; Golubev, P.; Heery, J. et al. (6 February 2023). "Spectroscopy along flerovium decay chains. II. Fine structure in odd-A 289Fl". Physical Review C 107 (2): L021301. doi:10.1103/PhysRevC.107.L021301. Bibcode: 2023PhRvC.107b1301C. 
  13. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties". Chinese Physics C 45 (3): 030001. doi:10.1088/1674-1137/abddae. https://www-nds.iaea.org/amdc/ame2020/NUBASE2020.pdf. 
  14. ↑ "Archived copy". http://www.nupecc.org/ecos/sh_0710.pdf. 
  15. ↑ 15.0 15.1 Armbruster, Peter; Münzenberg, Gottfried (1989). "Creating superheavy elements". Scientific American 34: 36–42. 
  16. ↑ 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. 
  17. ↑ Fleischmann, Martin; Pons, Stanley (1989). "Electrochemically induced nuclear fusion of deuterium". Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 261 (2): 301–308. doi:10.1016/0022-0728(89)80006-3. 
  18. ↑ Oganessian, Yu Ts; Demin, A. G.; Hussonnois, M.; Tretyakova, S. P.; Kharitonov, Yu P.; Utyonkov, V. K.; Shirokovsky, I. V.; Constantinescu, O. et al. (1984). "On the stability of the nuclei of element 108 with A=263–265". Zeitschrift für Physik A 319 (2): 215–217. doi:10.1007/BF01415635. Bibcode: 1984ZPhyA.319..215O. 
  19. ↑ 19.0 19.1 19.2 19.3 19.4 19.5 Barber, R. C.; Greenwood, N. N.; Hrynkiewicz, A. Z.; Jeannin, Y. P.; Lefort, M.; Sakai, M.; Ulehla, I.; Wapstra, A. P. et al. (1993). "Discovery of the transfermium elements. Part II: Introduction to discovery profiles. Part III: Discovery profiles of the transfermium elements (Note: for Part I see Pure Appl. Chem., Vol. 63, No. 6, pp. 879–886, 1991)". Pure and Applied Chemistry 65 (8): 1757. doi:10.1351/pac199365081757. 
  20. ↑ 20.0 20.1 Münzenberg, G.; Armbruster, P.; Folger, H.; Heßberger, F. P.; Hofmann, S.; Keller, J.; Poppensieker, K.; Reisdorf, W. et al. (1984). "The identification of element 108". Zeitschrift für Physik A 317 (2): 235–236. doi:10.1007/BF01421260. Bibcode: 1984ZPhyA.317..235M. 
  21. ↑ Hofmann, S. (1998). "New elements – approaching". Reports on Progress in Physics 61 (6): 639–689. doi:10.1088/0034-4885/61/6/002. Bibcode: 1998RPPh...61..639H. 
  22. ↑ Hofmann, S.; Heßberger, F.P.; Ninov, V.; Armbruster, P.; Münzenberg, G.; Stodel, C.; Popeko, A.G.; Yeremin, A.V. et al. (1997). "Excitation function for the production of 265 108 and 266 109". Zeitschrift für Physik A 358 (4): 377–378. doi:10.1007/s002180050343. Bibcode: 1997ZPhyA.358..377H. 
  23. ↑ Münzenberg, G.; Armbruster, P.; Berthes, G.; Folger, H.; Heßberger, F. P.; Hofmann, S.; Poppensieker, K.; Reisdorf, W. et al. (1986). "Evidence for264108, the heaviest known even-even isotope". Zeitschrift für Physik A 324 (4): 489–490. doi:10.1007/BF01290935. Bibcode: 1986ZPhyA.324..489M. 
  24. ↑ Mendeleev Symposium. Morita
  25. ↑ Dragojević, I.; Gregorich, K.; Düllmann, Ch.; Dvorak, J.; Ellison, P.; Gates, J.; Nelson, S.; Stavsetra, L. et al. (2009). "New Isotope 263108". Physical Review C 79 (1): 011602. doi:10.1103/PhysRevC.79.011602. Bibcode: 2009PhRvC..79a1602D. 
  26. ↑ Kaji, Daiya; Morimoto, Kouji; Sato, Nozomi; Ichikawa, Takatoshi; Ideguchi, Eiji; Ozeki, Kazutaka; Haba, Hiromitsu; Koura, Hiroyuki et al. (2009). "Production and Decay Properties of 263108". Journal of the Physical Society of Japan 78 (3): 035003. doi:10.1143/JPSJ.78.035003. Bibcode: 2009JPSJ...78c5003K. 
  27. ↑ "Flerov Laboratory of Nuclear Reactions". http://www1.jinr.ru/Reports/2008/english/06_flnr_e.pdf. [page needed]
  28. ↑ Tsyganov, Yu.; Oganessian, Yu.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Shirokovsky, I.; Polyakov, A.; Subbotin, V. et al. (2009-04-07). "Results of 226Ra+48Ca Experiment". http://www.np.ph.bham.ac.uk/iop09/iop_talks/07_04_09_Parallel_2/Y%20Tsyganov.ppt. [|permanent dead link|dead link}}] Alt URL
  29. ↑ Observation of 270Hs in the complete fusion reaction 36S+238U* R. Graeger et al., GSI Report 2008
  30. ↑ 30.0 30.1 Lazarev, Yu. A.; Lobanov, YV; Oganessian, YT; Tsyganov, YS; Utyonkov, VK; Abdullin, FS; Iliev, S; Polyakov, AN et al. (1995). "New Nuclide 267108 Produced by the 238U + 34S Reaction". Physical Review Letters 75 (10): 1903–1906. doi:10.1103/PhysRevLett.75.1903. PMID 10059158. Bibcode: 1995PhRvL..75.1903L. https://cds.cern.ch/record/284096/files/SCAN-9507002.pdf. 
  31. ↑ 31.0 31.1 "Decay properties of 269Hs and evidence for the new nuclide 270Hs" , Turler et al., GSI Annual Report 2001. Retrieved 2008-03-01.
  32. ↑ Dvorak, Jan (2006-09-25). "On the production and chemical separation of Hs (element 108)". Technical University of Munich. http://www2.ha.physik.uni-muenchen.de/heaviest_atoms/talks/Dvorak.pdf. 
  33. ↑ "Doubly magic 270Hs" , Turler et al., GSI report, 2006. Retrieved 2008-03-01.
  34. ↑ 34.0 34.1 Sonzogni, Alejandro. "Interactive Chart of Nuclides". National Nuclear Data Center: Brookhaven National Laboratory. http://www.nndc.bnl.gov/chart/reCenter.jsp?z=108&n=161. 
  35. ↑ Ghiorso, A.; Lee, D.; Somerville, L.; Loveland, W.; Nitschke, J.; Ghiorso, W.; Seaborg, G.; Wilmarth, P. et al. (1995). "Evidence for the possible synthesis of element 110 produced by the 59Co+209Bi reaction". Physical Review C 51 (5): R2293–R2297. doi:10.1103/PhysRevC.51.R2293. PMID 9970386. Bibcode: 1995PhRvC..51.2293G. 
  36. ↑ Hofmann, S.; Ninov, V.; Heßberger, F. P.; Armbruster, P.; Folger, H.; Münzenberg, G.; Schött, H. J.; Popeko, A. G. et al. (1995). "Production and decay of 269110". Zeitschrift für Physik A 350 (4): 277–280. doi:10.1007/BF01291181. Bibcode: 1995ZPhyA.350..277H. 
  37. ↑ Hofmann, S.; Heßberger, F. P.; Ackermann, D.; Antalic, S.; Cagarda, P.; Ćwiok, S.; Kindler, B.; Kojouharova, J. et al. (2001). "The new isotope 270110 and its decay products 266Hs and 262Sg". The European Physical Journal A 10 (1): 5–10. doi:10.1007/s100500170137. Bibcode: 2001EPJA...10....5H. http://www.dnp.fmph.uniba.sk/etext/68/text/Hofmann_et_al_EPJ_A10_(2001)_5.pdf. 
  38. ↑ Hofmann, S. (1998). "New elements – approaching". Reports on Progress in Physics 61 (6): 639–689. doi:10.1088/0034-4885/61/6/002. Bibcode: 1998RPPh...61..639H. 
  39. ↑ 39.0 39.1 Hofmann, S. (1996). "The new element 112". Zeitschrift für Physik A 354 (1): 229–230. doi:10.1007/BF02769517. Bibcode: 1996ZPhyA.354..229H. 
  40. ↑ 40.0 40.1 Public Affairs Department (26 October 2010). "Six New Isotopes of the Superheavy Elements Discovered: Moving Closer to Understanding the Island of Stability". Berkeley Lab. http://newscenter.lbl.gov/news-releases/2010/10/26/six-new-isotopes. 
  41. ↑ Yeremin, A. V.; Oganessian, Yu. Ts.; Popeko, A. G.; Bogomolov, S. L.; Buklanov, G. V.; Chelnokov, M. L.; Chepigin, V. I.; Gikal, B. N. et al. (1999). "Synthesis of nuclei of the superheavy element 114 in reactions induced by 48Ca". Nature 400 (6741): 242–245. doi:10.1038/22281. Bibcode: 1999Natur.400..242O. 
  42. ↑ 42.0 42.1 "Element 114 – Heaviest Element at GSI Observed at TASCA". http://www-win.gsi.de/kernchemie/English/Research/Elements/Element_114_eng.htm. 
  43. ↑ Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Shirokovsky, I.; Tsyganov, Yu.; Gulbekian, G. et al. (1999). "Synthesis of Superheavy Nuclei in the 48Ca+ 244Pu Reaction". Physical Review Letters 83 (16): 3154–3157. doi:10.1103/PhysRevLett.83.3154. Bibcode: 1999PhRvL..83.3154O. 
  44. ↑ 44.0 44.1 Oganessian, Yu. Ts. (2004). "Measurements of cross sections for the fusion-evaporation reactions 244Pu(48Ca,xn)292−x114 and 245Cm(48Ca,xn)293−x116". Physical Review C 69 (5): 054607. doi:10.1103/PhysRevC.69.054607. Bibcode: 2004PhRvC..69e4607O. http://link.aps.org/abstract/PRC/V69/E054607/. 
  45. ↑ 45.0 45.1 45.2 45.3 45.4 45.5 Audi et al. 2017, p. 030001-134.
  46. ↑ 46.0 46.1 46.2 46.3 46.4 46.5 46.6 Audi et al. 2017, p. 030001-133.
  47. ↑ Thoennessen, M. (2016). The Discovery of Isotopes: A Complete Compilation. Springer. pp. 229, 234, 238. doi:10.1007/978-3-319-31763-2. ISBN 978-3-319-31761-8. 
  48. ↑ Audi et al. 2017, p. 030001-135.
  49. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties". Chinese Physics C 45 (3): 030001. doi:10.1088/1674-1137/abddae. https://www-nds.iaea.org/amdc/ame2020/NUBASE2020.pdf. 
  50. ↑ Yu. Ts. Oganessian et al. (October 2000). "Synthesis of superheavy nuclei in 48Ca+244Pu interactions". Nuclei Experiment: Physics of Atomic Nuclei 63 (10): 1679–1687. doi:10.1134/1.1320137. Bibcode: 2000PAN....63.1679O. 
  51. ↑ Ninov, V. (1999). "Observation of Superheavy Nuclei Produced in the Reaction of 86Kr with 208Pb". Physical Review Letters 83 (6): 1104–1107. doi:10.1103/PhysRevLett.83.1104. Bibcode: 1999PhRvL..83.1104N. https://zenodo.org/record/1233919. 
  52. ↑ Public Affairs Department (21 July 2001). "Results of element 118 experiment retracted". Berkeley Lab. http://enews.lbl.gov/Science-Articles/Archive/118-retraction.html. 
  53. ↑ George Johnson (15 October 2002). "At Lawrence Berkeley, Physicists Say a Colleague Took Them for a Ride". The New York Times. https://www.nytimes.com/2002/10/15/science/at-lawrence-berkeley-physicists-say-a-colleague-took-them-for-a-ride.html?scp=2&sq=victor%20ninov&st=cse&pagewanted=1. 
  54. ↑ Robert Smolanczuk (1997). "Properties of the hypothetical spherical superheavy nuclei". Physical Review C 56 (2): 812–824. doi:10.1103/PhysRevC.56.812. Bibcode: 1997PhRvC..56..812S. 
  55. ↑ Oganessian, Yu. Ts.; Utyonkov, V. K.; Lobanov, Yu. V.; Abdullin, F. Sh.; Polyakov, A. N.; Shirokovsky, I. V.; Tsyganov, Yu. S.; Gulbekian, G. G. et al. (2000). "Synthesis of superheavy nuclei in 48Ca+244Pu interactions". Physics of Atomic Nuclei 63 (10): 1679–1687. doi:10.1134/1.1320137. Bibcode: 2000PAN....63.1679O. 
  56. ↑ Hofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Münzenberg, G.; Antalic, S.; Barth, W.; Burkhard, H. G. et al. (2016). "Review of even element super-heavy nuclei and search for element 120". The European Physical Journal A 2016 (52): 180. doi:10.1140/epja/i2016-16180-4. Bibcode: 2016EPJA...52..180H. https://zenodo.org/record/897926. 
  57. ↑ "TASCA in Small Image Mode Spectroscopy". http://www-win.gsi.de/tasca08/contributions/TASCA08_Cont_Andersson.pdf. 
  58. ↑ Hassium spectroscopy experiments at TASCA, A. Yakushev
  59. ↑ 59.0 59.1 Influence of entrance channels on formation of superheavy nuclei in massive fusion reactions, Zhao-Qing Feng, Jun-Qing Li, Gen-Ming Jin, April 2009
  60. ↑ 60.0 60.1 60.2 60.3 Feng, Z.; Jin, G.; Li, J. (2009). "Production of new superheavy Z=108–114 nuclei with 238U, 244Pu and 248,250Cm targets". Physical Review C 80: 057601. doi:10.1103/PhysRevC.80.057601. 

Isotopic compositions and standard atomic masses from:

Half-life, spin, and isomer data selected from:



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