Calcium-44

Isotopes of calcium

Isotopes of calcium

Nuclides with atomic number of 20 but with different mass numbers

Calcium (20Ca) has 26 known isotopes, ranging from 35Ca to 60Ca. There are five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca and 46Ca), plus one isotope (48Ca) with such a long half-life that it is for all practical purposes stable. The most abundant isotope, 40Ca, as well as the rare 46Ca, are theoretically unstable on energetic grounds, but their decay has not been observed. Calcium also has a cosmogenic isotope, 41Ca, with half-life 99,400 years. Unlike cosmogenic isotopes that are produced in the air, 41Ca is produced by neutron activation of 40Ca. Most of its production is in the upper metre of the soil column, where the cosmogenic neutron flux is still strong enough. 41Ca has received much attention in stellar studies because it decays to 41K, a critical indicator of solar system anomalies. The most stable artificial isotopes are 45Ca with half-life 163 days and 47Ca with half-life 4.5 days. All other calcium isotopes have half-lives of minutes or less.[4]

Quick Facts Main isotopes, Decay ...

40Ca comprises about 97% of natural calcium. 40Ca, like 40Ar, is a decay product of 40K. While K–Ar dating has been used extensively in the geological sciences, the prevalence of 40Ca in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution have been used for K–Ca age dating.

List of isotopes

More information Nuclide, Z ...
  1. [n 1]
    ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  2. [n 2]
    Bold half-life – nearly stable, half-life longer than age of universe.
  3. [n 3]
    Modes of decay:
    EC:Electron capture
    n:Neutron emission
    p:Proton emission
  4. [n 4]
    Bold symbol as daughter – Daughter product is stable.
  5. [n 5]
    ( ) spin value – Indicates spin with weak assignment arguments.
  6. [n 6]
    # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  7. [n 7]
    Heaviest observationally stable nuclide with equal numbers of protons and neutrons
  8. [n 8]
    Believed to undergo double electron capture to 40Ar with a half-life no less than 9.9×1021 y
  9. [n 9]
    Cosmogenic nuclide
  10. [N 10]
    Believed to undergo β−β− decay to 46Ti
  11. [N 11]
    Primordial radionuclide
  12. [N 12]
    Believed to be capable of undergoing triple beta decay with very long partial half-life
  13. [N 13]
    Lightest nuclide known to undergo double beta decay
  14. [N 14]
    Theorized to also undergo β− decay to 48Sc with a partial half-life exceeding 1.1+0.8
    −0.6    ×1021 years[6]

Calcium-48

Main article: Calcium-48
About 2 g of calcium-48

Calcium-48 is a doubly magic nucleus with 28 neutrons; unusually neutron-rich for a light primordial nucleus. It decays via double beta decay with an extremely long half-life of about 6.4×1019 years, though single beta decay is also theoretically possible.[7] This decay can analyzed with the sd nuclear shell model, and it is more energetic (4.27 MeV) than any other double beta decay.[8] It can also be used as a precursor for neutron-rich and superheavy nuclei.[9][10]

Calcium-60

Calcium-60 is the heaviest known isotope as of 2020.[1] First observed in 2018 at Riken alongside 59Ca and seven isotopes of other elements,[11] its existence suggests that there are additional even-N isotopes of calcium up to at least 70Ca, while 59Ca is probably the last bound isotope with odd N.[12] Earlier predictions had estimated the neutron drip line to occur at 60Ca, with 59Ca unbound.[11]

In the neutron-rich region, N = 40 becomes a magic number, so 60Ca was considered early on to be a possibly doubly magic nucleus, as is observed for the 68Ni isotone.[13][14] However, subsequent spectroscopic measurements of the nearby nuclides 56Ca, 58Ca, and 62Ti instead predict that it should lie on the island of inversion known to exist around 64Cr.[14][15]

References

  1. [1]
    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. [2]
    "Standard Atomic Weights: Calcium". CIAAW. 1983.
  3. [3]
    Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. [4]
    Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
  5. [5]
    Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  6. [6]
    Aunola, M.; Suhonen, J.; Siiskonen, T. (1999). "Shell-model study of the highly forbidden beta decay 48Ca → 48Sc". EPL. 46 (5): 577. Bibcode:1999EL.....46..577A. doi:10.1209/epl/i1999-00301-2. S2CID 250836275.
  7. [7]
    Arnold, R.; et al. (NEMO-3 Collaboration) (2016). "Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of 48Ca with the NEMO-3 detector". Physical Review D. 93 (11): 112008. arXiv:1604.01710. Bibcode:2016PhRvD..93k2008A. doi:10.1103/PhysRevD.93.112008.
  8. [8]
    Balysh, A.; et al. (1996). "Double Beta Decay of 48Ca". Physical Review Letters. 77 (26): 5186–5189. arXiv:nucl-ex/9608001. Bibcode:1996PhRvL..77.5186B. doi:10.1103/PhysRevLett.77.5186. PMID 10062737.
  9. [9]
    Notani, M.; et al. (2002). "New neutron-rich isotopes, 34Ne, 37Na and 43Si, produced by fragmentation of a 64A MeV 48Ca beam". Physics Letters B. 542 (1–2): 49–54. Bibcode:2002PhLB..542...49N. doi:10.1016/S0370-2693(02)02337-7.
  10. [10]
    Oganessian, Yu. Ts.; et al. (October 2006). "Synthesis of the isotopes of elements 118 and 116 in the 249Cf and 245Cm + 48Ca fusion reactions". Physical Review C. 74 (4): 044602. Bibcode:2006PhRvC..74d4602O. doi:10.1103/PhysRevC.74.044602.
  11. [11]
    Tarasov, O. B.; Ahn, D. S.; Bazin, D.; et al. (11 July 2018). "Discovery of 60Ca and Implications For the Stability of 70Ca". Physical Review Letters. 121 (2). doi:10.1103/PhysRevLett.121.022501.
  12. [12]
    Neufcourt, Léo; Cao, Yuchen; Nazarewicz, Witold; et al. (14 February 2019). "Neutron Drip Line in the Ca Region from Bayesian Model Averaging". Physical Review Letters. 122 (6). arXiv:1901.07632. doi:10.1103/PhysRevLett.122.062502.
  13. [13]
    Gade, A.; Janssens, R. V. F.; Weisshaar, D.; et al. (21 March 2014). "Nuclear Structure Towards N = 40 60Ca: In-Beam γ -Ray Spectroscopy of 58, 60Ti". Physical Review Letters. 112 (11). arXiv:1402.5944. doi:10.1103/PhysRevLett.112.112503.
  14. [14]
    Cortés, M.L.; Rodriguez, W.; Doornenbal, P.; et al. (January 2020). "Shell evolution of N = 40 isotones towards 60Ca: First spectroscopy of 62Ti". Physics Letters B. 800: 135071. arXiv:1912.07887. doi:10.1016/j.physletb.2019.135071.
  15. [15]
    Chen, S.; Browne, F.; Doornenbal, P.; et al. (August 2023). "Level structures of 56, 58Ca cast doubt on a doubly magic 60Ca". Physics Letters B. 843: 138025. arXiv:2307.07077. doi:10.1016/j.physletb.2023.138025.

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