Isotopes of nobelium

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Nobelium (No) 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 (and correctly identified) was 254No in 1966. There are 12 known radioisotopes which are 250No to 260No and 262No, and 3 isomers, 251mNo, 253mNo, and 254mNo. The longest-lived isotope is 259No with a half-life of 58 minutes. The longest-lived isomer is 251mNo with a half-life of 1.7 seconds.

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[1][n 1]
daughter
isotope(s)
nuclear
spin
excitation energy
250No 102 148 250.08756(22)# 5.7(8) µs SF (99.95%) (various) 0+
α (.05%) 246Fm
β+ (2.5×10−4%) 250Md
251No 102 149 251.08894(12)# 0.78(2) s α (89%) 247Fm 7/2+#
SF (10%) (various)
β+ (1%) 251Md
251mNo 110(180)# keV 1.7(10) s 9/2-#
252No 102 150 252.088967(10) 2.27(14) s α (73.09%) 248Fm 0+
SF (26.9%) (various)
β+ (1%) 252Md
253No[n 2] 102 151 253.090564(7) 1.62(15) min α (80%) 249Fm (9/2-)#
β+ (20%) 253Md
SF (10−3%) (various)
253mNo 129(19) keV 31 µs 5/2+#
254No 102 152 254.090956(11) 51(10) s α (89.3%) 250Fm 0+
β+ (10%) 254Md
SF (.31%) (various)
254mNo 500(100)# keV 0.28(4) s IT (80%) 254No 0+
α (20%) 250Fm
255No 102 153 255.093191(16) 3.1(2) min α (61.4%) 251Fm (1/2+)
β+ (38.6%) 255Md
256No 102 154 256.094283(8) 2.91(5) s α (99.44%) 252Fm 0+
SF (.55%) (various)
EC (.01%) 256Md
257No 102 155 257.096888(7) 25(2) s α (99%) 253Fm (7/2+)
β+ (1%) 257Md
258No 102 156 258.09821(11)# 1.2(2) ms SF (99.99%) (various) 0+
α (.01%) 254Fm
β+β+ (rare) 258Fm
259No 102 157 259.10103(11)# 58(5) min α (75%) 255Fm (9/2+)#
EC (25%) 259Md
SF (10%) (various)
260No 102 158 260.10264(22)# 106(8) ms SF (various) 0+
262No[n 3] 102 160 262.10746(39)# ~5 ms SF (various) 0+
  1. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
    SF: Spontaneous fission
  2. ^ Not directly synthesized, occurs as decay product of 257Rf
  3. ^ Not directly synthesized, occurs as decay product of 262Lr

Notes[edit]

  • 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.

Nucleosynthesis[edit]

By cold fusion[edit]

208Pb(48Ca,xn)256-xNo (x=1,2,3,4)

This cold fusion reaction was first studied in 1979 at the FLNR. Further work in 1988 at the 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 the Jyvaskylan 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 µs, 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 µs.

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)

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 36µs. 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 5.6µs and 54µs and assigned to 250No and 249No, respectively. The latter activity was later assigned to a K-isomer in 250No.[2] 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.[3]

By hot fusion[edit]

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 the 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 the 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 µs 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 an 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[edit]

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[edit]

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
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  ? 254Es + 22Ne,18O,13C - transfer
261No unknown
262No 1988 254Es + 22Ne - transfer (EC of 262Lr)

Nuclear isomerism[edit]

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 µs 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 µs, 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 54µs. 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 3.7µs.

Chemical yields of isotopes[edit]

Cold fusion[edit]

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[edit]

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[edit]

In 2003, scientists at the FLNR claimed to have discovered the lightest known isotope of nobelium. However, subsequent work showed that the 54 µs activity was actually due to 250No and the isotope 249No was retracted.

References[edit]

  1. ^ http://www.nucleonica.net/unc.aspx
  2. ^ Belozerov et al., 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. (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. doi:10.1140/epja/i2002-10109-6. 
  3. ^ D. Peterson 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. 


Isotopes of mendelevium Isotopes of nobelium Isotopes of lawrencium
Table of nuclides