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Lawrencium (₁₀₃Lr) 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 Lr in 1961. There are fourteen known isotopes from Lr to Lr, except Lr and Lr, and seven isomers. The longest-lived known isotope is Lr with a half-life of 11 hours.

List of isotopes

1. Lr – 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. ( ) spin value – Indicates spin with weak assignment arguments.
6. ^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
7. The experiment in which alpha decay of two Lr states was reported did not take into account spontaneous fission branches.
8. Not directly synthesized, occurs as a decay product of Db
9. Not directly synthesized, occurs as a decay product of Mc
10. Not directly synthesized, occurs as a decay product of Ts

Nucleosynthesis

Cold fusion

Tl(Ti,xn)Lr (x=2)

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Evidence was provided for the formation of Lr in the 2n exit channel. In 2022, two states (Lr and Lr) were found.

Tl(Ti,xn)Lr (x=2)

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. In 2022, two states (Lr and Lr) were found.

Pb(Ti,pxn)Lr (x=1?)

This reaction was reported in 1984 by Yuri Oganessian at the FLNR. The team was able to detect decays of Cf, a descendant of Lr.

Pb(Sc,xn)Lr

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Results are not readily available.

Bi(Ca,xn)Lr (x=2)

This reaction has been used to study the spectroscopic properties of Lr. The team at GANIL used the reaction in 2003 and the team at the FLNR used it between 2004–2006 to provide further information for the decay scheme of Lr. The work provided evidence for an isomeric level in Lr.

Hot fusion

Am(O,xn)Lr (x=5)

This reaction was first studied in 1965 by the team at the FLNR. They were able to detect activity with a characteristic decay of 45 seconds, which was assigned toLr or Lr. Later work suggests an assignment to Lr. Further studies in 1968 produced an 8.35–8.60 MeV alpha activity with a half-life of 35 seconds. This activity was also initially assigned to Lr or Lr and later to solely Lr.

Am(O,xn)Lr (x=4)

This reaction was studied in 1970 by the team at the FLNR. They were able to detect an 8.38 MeV alpha activity with a half-life of 20s. This was assigned toLr.

Cm(N,xn)Lr (x=3,4,5)

This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to assign alpha activities toLr,Lr and Lr from the 3-5n exit channels.

Cm(O,pxn)Lr (x=3,4)

This reaction was studied in 1988 at the LBNL in order to assess the possibility of producing Lr and Lr without using the exotic Es target. It was also used to attempt to measure an electron capture (EC) branch in Rf from the 5n exit channel. After extraction of the Lr(III) component, they were able to measure the spontaneous fission of Lr with an improved half-life of 44 minutes. The production cross-section was 700 pb. On this basis, a 14% electron capture branch was calculated if this isotope was produced via the 5n channel rather than the p4n channel. A lower bombarding energy (93 MeV c.f. 97 MeV) was then used to measure the production of Lr in the p3n channel. The isotope was successfully detected and a yield of 240 pb was measured. The yield was lower than expected compared to the p4n channel. However, the results were judged to indicate that the Lr was most likely produced by a p3n channel and an upper limit of 14% for the electron capture branch of Rf was therefore suggested.

Cm(N,xn)Lr (x=3?)

This reaction was studied briefly in 1958 at the LBNL using an enriched Cm target (5% Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25 seconds. Later results suggest a tentative assignment to Lr from the 3n channel

Cm(N,xn)Lr

This reaction was studied briefly in 1958 at the LBNL using an enriched Cm target (5% Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25s. Later results suggest a tentative assignment to Lr from the 3n channel with the Cm component. No activities assigned to reaction with the Cm component have been reported.

Bk(O,αxn)Lr (x=3)

This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to detect an activity assigned to Lr. The reaction was further studied in 1988 to study the aqueous chemistry of lawrencium. A total of 23 alpha decays were measured for Lr, with a mean energy of 8.03 MeV and an improved half-life of 2.7 minutes. The calculated cross-section was 8.7 nb.

Cf(B,xn)Lr (x=5,7??)

This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to Lr. Later results suggest a reassignment to Lr, resulting from the 5n exit channel. The 8.4 MeV activity was also assigned to Lr. Later results suggest a reassignment to Lr. This is most likely from the 33% Cf component in the target rather than from the 7n channel. The 8.2 MeV was subsequently associated with nobelium.

Cf(B,xn)Lr (x=4,6)

This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to Lr. Later results suggest a reassignment to Lr. The 8.4 MeV activity was also assigned to Lr. Later results suggest a reassignment to Lr. The 8.2 MeV was subsequently associated with nobelium.

Cf(N,αxn)Lr (x=3)

This reaction was studied in 1971 at the LBNL. They were able to identify a 0.7s alpha activity with two alpha lines at 8.87 and 8.82 MeV. This was assigned toLr.

Cf(B,xn)Lr (x=4)

This reaction was first studied in 1970 at the LBNL in an attempt to study the aqueous chemistry of lawrencium. They were able to measure a Lr activity. The reaction was repeated in 1976 at Oak Ridge and 26s Lr was confirmed by measurement of coincident X-rays.

Cf(C,pxn)Lr (x=2)

This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activity assigned to Lr from the p2n channel.

Cf(N,αxn)Lr (x=2,3)

This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activities assigned to Lr and Lr from the α2n and α3n and channels. The reaction was repeated in 1976 at Oak Ridge and the synthesis of Lr was confirmed.

Es + Ne – transfer

This reaction was studied in 1987 at the LLNL. They were able to detect new spontaneous fission (SF) activities assigned to Lr and Lr, resulting from transfer from the Ne nuclei to the Es target. In addition, a 5 ms SF activity was detected in delayed coincidence with nobelium K-shell X-rays and was assigned to No, resulting from the electron capture of Lr.

Decay products

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

Isotopes

Fourteen isotopes of lawrencium plus seven isomers have been synthesized with Lr being the longest-lived and the heaviest, with a half-life of 11 hours. Lr is the lightest isotope of lawrencium to be produced to date.

Lawrencium-253 isomers

A study of the decay properties of Db (see dubnium) in 2001 by Hessberger et al. at the GSI provided some data for the decay of Lr. Analysis of the data indicated the population of an isomeric level in Lr from the decay of the corresponding isomer in Db. The ground state was assigned spin and parity of 7/2−, decaying by emission of an 8794 keV alpha particle with a half-life of 0.57 s. The isomeric level was assigned spin and parity of 1/2−, decaying by emission of an 8722 keV alpha particle with a half-life of 1.49 s.

Lawrencium-255 isomers

Recent work on the spectroscopy of Lr formed in the reaction Bi(Ca,2n)Lr has provided evidence for an isomeric level.

References

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3. ^ Huang, T.; Seweryniak, D.; Back, B. B.; et al. (2022). "Discovery of the new isotope Lr: Impact of the hexacontetrapole deformation on single-proton orbital energies near the Z = 100 deformed shell gap". Physical Review C. 106 (L061301). doi:10.1103/PhysRevC.106.L061301. S2CID 254300224.
4. Leppänen, A.-P. (2005). Alpha-decay and decay-tagging studies of heavy elements using the RITU separator (PDF) (Thesis). University of Jyväskylä. pp. 83–100. ISBN 978-951-39-3162-9. ISSN 0075-465X.
5. Vostinar, M.; Heßberger, F. P.; Ackermann, D.; Andel, B.; Antalic, S.; Block, M.; Droese, Ch.; Even, J.; Heinz, S.; Kalaninova, Z.; Kojouharov, I.; Laatiaoui, M.; Mistry, A. K.; Piot, J.; Savajols, H. (14 February 2019). "Alpha-gamma decay studies of 258Db and its (grand)daughter nuclei 254Lr and 250Md". The European Physical Journal A. 55 (2): 17. Bibcode:2019EPJA...55...17V. doi:10.1140/epja/i2019-12701-y. ISSN 1434-601X. S2CID 254115080. Retrieved 3 July 2023.
6. Meng Wang; et al. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references". Chinese Physics C. 45 (3): 030003. Bibcode:2021ChPhC..45c0003W. doi:10.1088/1674-1137/abddaf. S2CID 235282522.
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. Chatillon, A.; Theisen, Ch.; Greenlees, P. T.; Auger, G.; Bastin, J. E.; Bouchez, E.; Bouriquet, B.; Casandjian, J. M.; Cee, R.; Clément, E.; Dayras, R.; de France, G.; de Toureil, R.; Eeckhaudt, S.; Görgen, A.; Grahn, T.; Grévy, S.; Hauschild, K.; Herzberg, R. -D.; Ikin, P. J. C.; Jones, G. D.; Jones, P.; Julin, R.; Juutinen, S.; Kettunen, H.; Korichi, A.; Korten, W.; Le Coz, Y.; Leino, M.; Lopez-Martens, A.; Lukyanov, S. M.; Penionzhkevich, Yu. E.; Perkowski, J.; Pritchard, A.; Rahkila, P.; Rejmund, M.; Saren, J.; Scholey, C.; Siem, S.; Saint-Laurent, M. G.; Simenel, C.; Sobolev, Yu. G.; Stodel, Ch.; Uusitalo, J.; Villari, A.; Bender, M.; Bonche, P.; Heenen, P. -H. (1 November 2006). "Spectroscopy and single-particle structure of the odd- Z heavy elements 255Lr, 251Md and 247Es". The European Physical Journal A - Hadrons and Nuclei. 30 (2): 397–411. Bibcode:2006EPJA...30..397C. doi:10.1140/epja/i2006-10134-5. ISSN 1434-601X. S2CID 123346991. Retrieved 3 July 2023.
9. Heßberger, F. P.; Antalic, S.; Mistry, A. K.; Ackermann, D.; Andel, B.; Block, M.; Kalaninova, Z.; Kindler, B.; Kojouharov, I.; Laatiaoui, M.; Lommel, B.; Piot, J.; Vostinar, M. (20 July 2016). "Alpha- and EC-decay measurements of 257Rf". The European Physical Journal A. 52 (7): 192. Bibcode:2016EPJA...52..192H. doi:10.1140/epja/i2016-16192-0. ISSN 1434-601X. S2CID 254108438. Retrieved 3 July 2023.
10. Haba, H.; Huang, M.; Kaji, D.; Kanaya, J.; Kudou, Y.; Morimoto, K.; Morita, K.; Murakami, M.; Ozeki, K.; Sakai, R.; Sumita, T.; Wakabayashi, Y.; Yoneda, A.; Kasamatsu, Y.; Kikutani, Y.; Komori, Y.; Nakamura, K.; Shinohara, A.; Kikunaga, H.; Kudo, H.; Nishio, K.; Toyoshima, A.; Tsukada, K. (28 February 2014). "Production of 262Db in the 248Cm(19F,5n)262Db reaction and decay properties of 262Db and 258Lr". Physical Review C. 89 (2): 024618. doi:10.1103/PhysRevC.89.024618. Retrieved 2 July 2023.
11. ^ Hulet, E. K. (22 October 1990). New, heavy transuranium isotopes. Robert A. Welch Foundation conference on chemical research: fifty years with transuranium elements. Lawrence Livermore National Lab., CA (USA). OSTI 6028419. Retrieved 3 July 2023.

• 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. S2CID 250839471.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

v t e Isotopes of the chemical elements
Group 1 2   3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Period Hydrogen and alkali metals Alkaline earth metals Pnicto­gens Chal­co­gens Halo­gens Noble gases ① Isotopes § ListH1 Isotopes § ListHe2 ② Isotopes § ListLi3 Isotopes § ListBe4 Isotopes § ListB5 Isotopes § ListC6 Isotopes § ListN7 Isotopes § ListO8 Isotopes § ListF9 Isotopes § ListNe10 ③ Isotopes § ListNa11 Isotopes § ListMg12 Isotopes § ListAl13 Isotopes § ListSi14 Isotopes § ListP15 Isotopes § ListS16 Isotopes § ListCl17 Isotopes § ListAr18 ④ Isotopes § ListK19 Isotopes § ListCa20 Isotopes § ListSc21 Isotopes § ListTi22 Isotopes § ListV23 Isotopes § ListCr24 Isotopes § ListMn25 Isotopes § ListFe26 Isotopes § ListCo27 Isotopes § ListNi28 Isotopes § ListCu29 Isotopes § ListZn30 Isotopes § ListGa31 Isotopes § ListGe32 Isotopes § ListAs33 Isotopes § ListSe34 Isotopes § ListBr35 Isotopes § ListKr36 ⑤ Isotopes § ListRb37 Isotopes § ListSr38 Isotopes § ListY39 Isotopes § ListZr40 Isotopes § ListNb41 Isotopes § ListMo42 Isotopes § ListTc43 Isotopes § ListRu44 Isotopes § ListRh45 Isotopes § ListPd46 Isotopes § ListAg47 Isotopes § ListCd48 Isotopes § ListIn49 Isotopes § ListSn50 Isotopes § ListSb51 Isotopes § ListTe52 Isotopes § ListI53 Isotopes § ListXe54 ⑥ Isotopes § ListCs55 Isotopes § ListBa56 Isotopes § ListLu71 Isotopes § ListHf72 Isotopes § ListTa73 Isotopes § ListW74 Isotopes § ListRe75 Isotopes § ListOs76 Isotopes § ListIr77 Isotopes § ListPt78 Isotopes § ListAu79 Isotopes § ListHg80 Isotopes § ListTl81 Isotopes § ListPb82 Isotopes § ListBi83 Isotopes § ListPo84 Isotopes § ListAt85 Isotopes § ListRn86 ⑦ Isotopes § ListFr87 Isotopes § ListRa88 Isotopes § ListLr103 Isotopes § ListRf104 Isotopes § ListDb105 Isotopes § ListSg106 Isotopes § ListBh107 Isotopes § ListHs108 Isotopes § ListMt109 Isotopes § ListDs110 Isotopes § ListRg111 Isotopes § ListCn112 Isotopes § ListNh113 Isotopes § ListFl114 Isotopes § ListMc115 Isotopes § ListLv116 Isotopes § ListTs117 Isotopes § ListOg118 ⑧ Isotopes § ListUue119 Isotopes § ListUbn120 Isotopes § ListLa57 Isotopes § ListCe58 Isotopes § ListPr59 Isotopes § ListNd60 Isotopes § ListPm61 Isotopes § ListSm62 Isotopes § ListEu63 Isotopes § ListGd64 Isotopes § ListTb65 Isotopes § ListDy66 Isotopes § ListHo67 Isotopes § ListEr68 Isotopes § ListTm69 Isotopes § ListYb70   Isotopes § ListAc89 Isotopes § ListTh90 Isotopes § ListPa91 Isotopes § ListU92 Isotopes § ListNp93 Isotopes § ListPu94 Isotopes § ListAm95 Isotopes § ListCm96 Isotopes § ListBk97 Isotopes § ListCf98 Isotopes § ListEs99 Isotopes § ListFm100 Isotopes § ListMd101 Isotopes § ListNo102
Table of nuclides Categories: Isotopes Tables of nuclides Metastable isotopes Isotopes by element

• Isotopes of lawrencium
• Lawrencium
• Lists of isotopes by element