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Isotopes of nobelium

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Nobelium (102No) 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 (and correctly identified) was 254No in 1966. There are fourteen known radioisotopes, which are 248No to 260No and 262No, and many isomers. The longest-lived isotope is 259No with a half-life of 58 minutes. The longest-lived isomer is 251m1No with a half-life of 1.02 seconds.

Isotopes of nobelium (102No)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
253No synth 1.6 min α55% 249Fm
β+45% 253Md
254No synth 51 s α90% 250Fm
β+10% 254Md
255No synth 3.5 min α61% 251Fm
β+39% 255Md
257No synth 25 s α99% 253Fm
β+1% 257Md
259No synth 58 min α75% 255Fm
ε25% 259Md
SF<10% –

List of isotopes

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Nuclide
[n 1] 		Z N Isotopic mass (Da)
[n 2][n 3] 		Half-life
 Decay
mode
[n 4] 		Daughter
isotope
 Spin and
parity
[n 5][n 6]
Excitation energy[n 6]
248No 102 146 248.08662(24)# <2 μs 0+
249No[2][3] 102 147 249.0878(3)# 38.3(28) ms α 245Fm 5/2+
SF (<0.23%) (various)
250No[4] 102 148 250.08756(22)# 4.0(4) μs SF (various) 0+
α (rare) 246Fm
250m1No ~1250 keV 23(4) μs IT 250No (6+)
SF (<3.5%) (various)
250m2No 0.7+1.4
−0.3 μs 		IT 250m1No
251No[5] 102 149 251.088945(4)[6] 0.80(1) s α (91%)[5] 247Fm (7/2+)
β+ (9%) 251Md
SF (0.14%) (various)
251m1No 105(3) keV[7] 1.02(3) s α 247mFm (1/2+)
β+? 251Md
251m2No >1700 keV ~2 μs IT 251No
252No[8] 102 150 252.088967(10) 2.42(6) s α (70.1%) 248Fm 0+
SF (29.1%) (various)
β+ (0.8%) 252Md
252m1No 1254 keV 100(3) ms IT 252No (8−)
252m2No 921(118) μs IT 252No
253No[1] 102 151 253.090564(7) 1.57(2) min α (55%) 249Fm (9/2−)
β+ (45%) 253Md
SF (rare) (various)
253m1No 167.5(5) keV 30.3(1.6) μs IT 253No (5/2+)
253m2No 1196(107) keV 706(24) μs IT 253No 19/2+#
253m3No 1256(113) keV 552(15) μs IT 253No 25/2+#
254No[1] 102 152 254.090956(11) 51.2(4) s α (90%) 250Fm 0+
β+ (10%) 254Md
SF (0.17%) (various)
254m1No 1296.4(1.1) keV 264.9(1.4) ms IT (98.0%) 254No (8−)
SF (2.0%) (various)
α (<1%) 250Fm
254m2No 3217(300)# keV 184(3) μs IT 254m1No 16+#
SF (<1.2%) (various)
255No[9] 102 153 255.093191(16) 3.52(18) min[1] α (61.4%) 251Fm 1/2+
β+ (38.6%) 255Md
255m1No 240–300 keV 109(9) μs IT 255No (11/2−)
255m2No 1400–1600 keV 77(6) μs IT 255m1No (19/2,21/2,23/2)
255m3No ≥1500 keV 1.2+0.6
−0.4 μs 		IT 255m1No (≥19/2)
256No[10] 102 154 256.094283(8) 2.91(5) s α (99.47%) 252Fm 0+
SF (0.53%) (various)
EC (rare) 256Md
256mNo[11] 7.8+8.3
−2.6 μs 		IT 256No (5−,7−)
257No[12] 102 155 257.096888(7) 24.5(5) s α 253Fm (3/2+)
β+ (rare) 257Md
258No[1] 102 156 258.09821(11)# 1.23(12) ms SF (various) 0+
α (rare) 254Fm
259No 102 157 259.10103(11)# 58(5) min α (75%) 255Fm 9/2+
EC (25%) 259Md
SF (<10%)[13]) (various)
260No 102 158 260.10264(22)# 106(8) ms SF (various) 0+
262No[n 7] 102 160 262.10746(39)# ~5 ms SF (various) 0+
This table header & footer:
  1. ^ mNo – 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:
    EC: Electron capture
    IT: Isomeric transition
    SF: Spontaneous fission
  5. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  6. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  7. ^ Not directly synthesized, occurs as decay product of 262Lr

Nucleosynthesis

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Cold fusion

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208Pb(48Ca,xn)256−xNo (x=1,2,3,4)

This cold fusion reaction was first studied in 1979 at Flerov Laboratory of Nuclear Reactions (FLNR). Further work in 1988 at GSI measured EC and SF branchings in 254No. In 1989, the FLNR used the reaction to measure SF decay characteristics for the two isomers of 254No. The measurement of the 2n excitation function was reported in 2001 by Yuri Oganessian at the FLNR.

Patin et al. at the LBNL reported in 2002 the synthesis of 255–251No in the 1-4n exit channels and measured further decay data for these isotopes.

The reaction has recently been used at Jyväskylän Yliopisto Fysiikan Laitos (JYFL) using the RITU set-up to study K-isomerism in 254No. The scientists were able to measure two K-isomers with half-lives of 275 ms and 198 s, respectively. They were assigned to 8− and 16+ K-isomeric levels.

The reaction was used in 2004–5 at the FLNR to study the spectroscopy of 255–253No. The team were able to confirm an isomeric level in 253No with a half-life of 43.5 s.

208Pb(44Ca,xn)252−xNo (x=2)

This reaction was studied in 2003 at the FLNR in a study of the spectroscopy of 250No.

207Pb(48Ca,xn)255−xNo (x=2)

The measurement of the 2n excitation function for this reaction was reported in 2001 by Yuri Oganessian and co-workers at the FLNR. The reaction was used in 2004–5 to study the spectroscopy of 253No.

206Pb(48Ca,xn)254−xNo (x=1,2,3,4)

The measurement of the 1-4n excitation functions for this reaction were reported in 2001 by Yuri Oganessian and co-workers at the FLNR. The 2n channel was further studied by the GSI to provide a spectroscopic determination of K-isomerism in 252No. A K-isomer with spin and parity 8− was detected with a half-life of 110 ms.

204Pb(48Ca,xn)252−xNo (x=2,3)

The measurement of the 2n excitation function for this reaction was reported in 2001 by Yuri Oganessian at the FLNR. They reported a new isotope 250No with a half-life of 36 μs. The reaction was used in 2003 to study the spectroscopy of 250No.They were able to observe two spontaneous fission activities with half-lives of 5.6 μs and 54 μs and assigned to 250No and 249No, respectively. The latter activity was later assigned to a K-isomer in 250No.[14] The reaction was reported in 2006 by Peterson et al. at the Argonne National Laboratory (ANL) in a study of SF in 250No. They detected two activities with half-lives of 3.7  μs and 43  μs and both assigned to 250No, the latter associated with a K-isomer.[15] In 2020, a team at FLNR repeated this reaction and found a new 9.1-MeV alpha particle activity correlated to 245Fm and 241Cf, which they assigned to the new isotope 249No.[2]

Hot fusion

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232Th(26Mg,xn)258−xNo (x=4,5,6)

The cross sections for the 4-6n exit channels have been measured for this reaction at the FLNR.

238U(22Ne,xn)260−xNo (x=4,5,6)

This reaction was first studied in 1964 at FLNR. The team were able to detect decays from 252Fm and 250Fm. The 252Fm activity was associated with an ~8 s half-life and assigned to 256102 from the 4n channel, with a yield of 45 nb. They were also able to detect a 10 s spontaneous fission activity also tentatively assigned to 256102. Further work in 1966 on the reaction examined the detection of 250Fm decay using chemical separation and a parent activity with a half-life of ~50 s was reported and correctly assigned to 254102. They also detected a 10 s spontaneous fission activity tentatively assigned to 256102. The reaction was used in 1969 to study some initial chemistry of nobelium at the FLNR. They determined eka-ytterbium properties, consistent with nobelium as the heavier homologue. In 1970, they were able to study the SF properties of 256No. In 2002, Patin et al. reported the synthesis of 256No from the 4n channel but were unable to detect 257No.

The cross section values for the 4-6n channels have also been studied at the FLNR.

238U(20Ne,xn)258−xNo

This reaction was studied in 1964 at FLNR. No spontaneous fission activities were observed.

236U(22Ne,xn)258−xNo (x=4,5,6)

The cross sections for the 4-6n exit channels have been measured for this reaction at the FLNR.

235U(22Ne,xn)257−xNo (x=5)

This reaction was studied in 1970 at the FLNR. It was used to study the SF decay properties of 252No.

233U(22Ne,xn)255−xNo

The synthesis of neutron deficient nobelium isotopes was studied in 1975 at the FLNR. In their experiments they observed a 250 s SF activity, which they tentatively assigned to 250No in the 5n exit channel. Later results have not been able to confirm this activity and it is currently unidentified.

242Pu(18O,xn)260−xNo (x=4?)

This reaction was studied in 1966 at the FLNR. The team identified an 8.2 s SF activity tentatively assigned to 256102.

241Pu(16O,xn)257−xNo

This reaction was first studied in 1958 at the FLNR. The team measured ~8.8 MeV alpha particles with a half-life of 30 s and assigned to 253,252,251102. A repeat in 1960 produced 8.9 MeV alpha particles with a half-life of 2–40 s and assigned to 253102 from the 4n channel. Confidence in these results was later diminished.

239Pu(18O,xn)257−xNo (x=5)

This reaction was studied in 1970 at the FLNR in an effort to study the SF decay properties of 252No.

239Pu(16O,xn)255−xNo

This reaction was first studied in 1958 at the FLNR. The team were able to measure ~8.8 MeV alpha particles with a half-life of 30 s and assigned to253,252,251102. A repeat in 1960 was unsuccessful and it was concluded the first results were probably associated with background effects.

243Am(15N,xn)258−xNo (x=4)

This reaction was studied in 1966 at the FLNR. The team were able to detect 250Fm using chemical techniques and determined an associated half-life significantly higher than the reported 3 s by Berkeley for the supposed parent 254No. Further work later the same year measured 8.1 MeV alpha particles with a half-life of 30–40 s.

243Am(14N,xn)257−xNo

This reaction was studied in 1966 at the FLNR. They were unable to detect the 8.1 MeV alpha particles detected when using a N-15 beam.

241Am(15N,xn)256−xNo (x=4)

The decay properties of 252No were examined in 1977 at Oak Ridge. The team calculated a half-life of 2.3 s and measured a 27% SF branching.

248Cm(18O,αxn)262−xNo (x=3)

The synthesis of the new isotope 259No was reported in 1973 from the LBNL using this reaction.

248Cm(13C,xn)261−xNo (x=3?,4,5)

This reaction was first studied in 1967 at the LBNL. The new isotopes 258No,257No and 256No were detected in the 3-5n channels. The reaction was repeated in 1970 to provide further decay data for 257No.

248Cm(12C,xn)260−xNo (4,5?)

This reaction was studied in 1967 at the LBNL in their seminal study of nobelium isotopes. The reaction was used in 1990 at the LBNL to study the SF of256No.

246Cm(13C,xn)259−xNo (4?,5?)

This reaction was studied in 1967 at the LBNL in their seminal study of nobelium isotopes.

246Cm(12C,xn)258−xNo (4,5)

This reaction was studied in 1958 by scientists at the LBNL using a 5% 246Cm curium target. They were able to measure 7.43 MeV decays from250Fm, associated with a 3 s 254No parent activity, resulting from the 4n channel. The 3 s activity was later reassigned to 252No, resulting from reaction with the predominant 244Cm component in the target. It could however not be proved that it was not due to the contaminant250mFm, unknown at the time. Later work in 1959 produced 8.3 MeV alpha particles with a half-life of 3 s and a 30% SF branch. This was initially assigned to 254No and later reassigned to 252No, resulting from reaction with the 244Cm component in the target. The reaction was restudied in 1967 and activities assigned to 254No and 253No were detected.

244Cm(13C,xn)257−xNo (x=4)

This reaction was first studied in 1957 at the Nobel Institute in Stockholm. The scientists detected 8.5 MeV alpha particles with a half-life of 10 minutes. The activity was assigned to 251No or 253No. The results were later dismissed as background. The reaction was repeated by scientists at the LBNL in 1958 but they were unable to confirm the 8.5 MeV alpha particles. The reaction was further studied in 1967 at the LBNL and an activity assigned to 253No was measured.

244Cm(12C,xn)256−xNo (x=4,5)

This reaction was studied in 1958 by scientists at the LBNL using a 95% 244Cm curium target. They were able to measure 7.43 MeV decays from250Fm, associated with a 3 s 254No parent activity, resulting from the reaction (246Cm,4n). The 3 s activity was later reassigned to252No, resulting from reaction (244Cm,4n). It could however not be proved that it was not due to the contaminant 250mFm, unknown at the time. Later work in 1959 produced 8.3 MeV alpha particles with a half-life of 3 s and a 30% SF branch. This was initially assigned to 254No and later reassigned to 252No, resulting from reaction with the 244Cm component in the target. The reaction was restudied in 1967 at the LBNL and a new activity assigned to 251No was measured.

252Cf(12C,αxn)260−xNo (x=3?)

This reaction was studied at the LBNL in 1961 as part of their search for element 104. They detected 8.2 MeV alpha particles with a half-life of 15 s. This activity was assigned to a Z=102 isotope. Later work suggests an assignment to 257No, resulting most likely from the α3n channel with the 252Cf component of the californium target.

252Cf(11B,pxn)262−xNo (x=5?)

This reaction was studied at the LBNL in 1961 as part of their search for element 103. They detected 8.2 MeV alpha particles with a half-life of 15 s. This activity was assigned to a Z=102 isotope. Later work suggests an assignment to 257No, resulting most likely from the p5n channel with the 252Cf component of the californium target.

249Cf(12C,αxn)257−xNo (x=2)

This reaction was first studied in 1970 at the LBNL in a study of 255No. It was studied in 1971 at the Oak Ridge Laboratory. They were able to measure coincident Z=100 K X-rays from 255No, confirming the discovery of the element.

As decay products

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Isotopes of nobelium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:

Evaporation Residue Observed No isotope
262Lr 262No
269Hs, 265Sg, 261Rf 257No
267Hs, 263Sg, 259Rf 255No
254Lr 254No
261Sg, 257Rf 253No
264Hs, 260Sg, 256Rf 252No
255Rf 251No

Isotopes

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Twelve radioisotopes of nobelium have been characterized, with the most stable being 259No with a half-life of 58 minutes. Longer half-lives are expected for the as-yet-unknown 261No and 263No. An isomeric level has been found in 253No and K-isomers have been found in 250No, 252No and 254No to date.

Chronology of isotope discovery
Isotope Year discovered Discovery reaction
249No 2020 204Pb(48Ca,3n)
250Nom 2001 204Pb(48Ca,2n)
250Nog 2006 204Pb(48Ca,2n)
251No 1967 244Cm(12C,5n)
252Nog 1959 244Cm(12C,4n)
252Nom ~2002 206Pb(48Ca,2n)
253Nog 1967 242Pu(16O,5n),239Pu(18O,4n)
253Nom 1971 249Cf(12C,4n)
254Nog 1966 243Am(15N,4n)
254Nom1 1967? 246Cm(13C,5n),246Cm(12C,4n)
254Nom2 ~2003 208Pb(48Ca,2n)
255No 1967 246Cm(13C,4n),248Cm(12C,5n)
256No 1967 248Cm(12C,4n),248Cm(13C,5n)
257No 1961?, 1967 248Cm(13C,4n)
258No 1967 248Cm(13C,3n)
259No 1973 248Cm(18O,α3n)
260No 1985 254Es + 22Ne,18O,13C – transfer
262No 1988 254Es + 22Ne – transfer (EC of 262Lr)

Nuclear isomerism

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254No

The study of K-isomerism was recently studied by physicists at the University of Jyväskylä physics laboratory (JYFL). They were able to confirm a previously reported K-isomer and detected a second K-isomer. They assigned spins and parities of 8− and 16+ to the two K-isomers.

253No

In 1971, Bemis et al. was able to determine an isomeric level decaying with a half-life of 31 s from the decay of 257Rf. This was confirmed in 2003 at the GSI by also studying the decay of 257Rf. Further support in the same year from the FLNR appeared with a slightly higher half-life of 43.5 s, decaying by M2 gamma emission to the ground state.

252No

In a recent study by the GSI into K-isomerism in even-even isotopes, a K-isomer with a half-life of 110 ms was detected for 252No. A spin and parity of 8− was assigned to the isomer.

250No

In 2003, scientists at the FLNR reported that they had been able to synthesise 249No, which decayed by SF with a half-life of 54 μs. Further work in 2006 by scientists at the ANL showed that the activity was actually due to a K-isomer in 250No. The ground state isomer was also detected with a very short half-life of 3.7 μs.

Chemical yields of isotopes

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Cold fusion

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

Projectile Target CN 1n 2n 3n 4n
48Ca 208Pb 256No 254No: 2050 nb ; 22.3 MeV
48Ca 207Pb 255No 253No: 1310 nb ; 22.4 MeV
48Ca 206Pb 254No 253No: 58 nb ; 23.6 MeV 252No: 515 nb ; 23.3 MeV 251No: 30 nb ; 30.7 MeV 250No: 260 pb ; 43.9 MeV
48Ca 204Pb 252No 250No:13.2 nb ; 23.2 MeV

Hot fusion

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

Projectile Target CN 3n 4n 5n 6n
26Mg 232Th 258No 254No:1.6 nb 253No:9 nb 252No:8 nb
22Ne 238U 260No 256No:40 nb 255No:200 nb 254No:15 nb
22Ne 236U 258No 254No:7 nb 253No:25 nb 252No:15 nb

Retracted isotopes

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In 2003, scientists at the FLNR claimed to have discovered 249No, which would have been the lightest known isotope of nobelium. However, subsequent work showed that the 54 μs fission activity instead originated from an excited state of 250No.[15] The discovery of this isotope was later reported in 2020; its decay properties differed from the 2003 claims.[2]

References

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  1. ^ a b c d e Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ^ a b c Joint Institute for Nuclear Research, 2020 (PDF) (Report). 23 June 2021. pp. 117–118. Retrieved 26 June 2021.
  3. ^ Tezekbayeva, M. S.; Yeremin, A. V.; Svirikhin, A. I.; et al. (2022). "Study of the production and decay properties of neutron-deficient nobelium isotopes". The European Physical Journal A. 58 (52): 52. arXiv:2203.15659. Bibcode:2022EPJA...58...52T. doi:10.1140/epja/s10050-022-00707-9. S2CID 247720708.
  4. ^ Khuyagbaatar, J.; Brand, H.; Düllmann, Ch. E.; Heßberger, F. P.; Jäger, E.; Kindler, B.; Krier, J.; Kurz, N.; Lommel, B.; Nechiporenko, Yu.; Novikov, Yu. N.; Schausten, B.; Yakushev, A. (5 August 2022). "Search for fission from a long-lived isomer in 250No and evidence of a second isomer". Physical Review C. 106 (2): 024309. Bibcode:2022PhRvC.106b4309K. doi:10.1103/PhysRevC.106.024309. Retrieved 4 July 2023.
  5. ^ a b Heßberger, F. P.; Hofmann, S.; Ackermann, D.; et al. (1 December 2006). "Alpha-gamma decay studies of 255Rf, 251No and 247Fm". The European Physical Journal A - Hadrons and Nuclei. 30 (3): 561–569. Bibcode:2006EPJA...30..561H. doi:10.1140/epja/i2006-10137-2. ISSN 1434-601X. S2CID 123871572.
  6. ^ Kaleja, O.; Anđelić, B.; Bezrodnova, O.; et al. (2022). "Direct high-precision mass spectrometry of superheavy elements with SHIPTRAP". Physical Review C. 106 (5): 054325. Bibcode:2022PhRvC.106e4325K. doi:10.1103/PhysRevC.106.054325. hdl:10481/79072. S2CID 254365259.
  7. ^ Brankica Anđelić (2021). Direct mass measurements of No, Lr and Rf isotopes with SHIPTRAP and developments for chemical isobaric separation (PhD thesis). University of Groningen. doi:10.33612/diss.173546003.
  8. ^ Sulignano, Barbara. Search for K isomers in 252,254No and 260Sg and investigation of their nuclear structure (Thesis). Retrieved 4 July 2023.
  9. ^ Bronis, A.; Heßberger, F. P.; Antalic, S.; et al. (5 July 2022). "Decay studies of new isomeric states in 255No" (PDF). Physical Review C. 106 (1): 014602. Bibcode:2022PhRvC.106a4602B. doi:10.1103/PhysRevC.106.014602.
  10. ^ Hoffman, D. C.; Lee, D. M.; Gregorich, K. E.; et al. (1 February 1990). "Spontaneous fission properties of 2.9-s 256No". Physical Review C. 41 (2): 631–639. Bibcode:1990PhRvC..41..631H. doi:10.1103/PhysRevC.41.631. PMID 9966395.
  11. ^ Kessaci, K.; Gall, B. J. P.; Dorvaux, O.; et al. (11 October 2021). "Evidence of high-K isomerism in 256
    102    No
    154    ". Physical Review C. 104 (4): 044609. doi:10.1103/PhysRevC.104.044609. S2CID 240669370.
  12. ^ Asai, M.; Tsukada, K.; Sakama, M.; et al. (2 September 2005). "Experimental Identification of Spin-Parities and Single-Particle Configurations in 257No and Its α-Decay Daughter 253Fm". Physical Review Letters. 95 (10): 102502. Bibcode:2005PhRvL..95j2502A. doi:10.1103/PhysRevLett.95.102502. PMID 16196924.
  13. ^ "Table of Isotopes decay data".
  14. ^ Belozerov, A. V.; Chelnokov, M.L.; Chepigin, V.I.; Drobina, T.P.; Gorshkov, V.A.; Kabachenko, A.P.; Malyshev, O.N.; Merkin, I.M.; Oganessian, Yu.Ts.; et al. (2003). "Spontaneous-fission decay properties and production cross-sections for the neutron-deficient nobelium isotopes formed in the 44, 48Ca + 204, 206, 208Pb reactions". European Physical Journal A. 16 (4): 447–456. Bibcode:2003EPJA...16..447B. doi:10.1140/epja/i2002-10109-6. S2CID 120538375.
  15. ^ a b Peterson, D.; Back, B. B.; Janssens, R. V. F.; et al. (2006). "Decay modes of 250No". Physical Review C. 74 (014316). arXiv:nucl-ex/0604005. Bibcode:2006PhRvC..74a4316P. doi:10.1103/PhysRevC.74.014316. S2CID 117045537.
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