Isotopes of europium

Isotopes of europium (₆₃Eu)
β−	152Gd
Standard atomic weight Ar°(Eu)
	151.964±0.001; 151.96±0.01 (abridged);
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Naturally occurring europium (₆₃Eu) is composed of two isotopes, ¹⁵¹Eu and ¹⁵³Eu, with ¹⁵³Eu being the most abundant (52.2% natural abundance). While ¹⁵³Eu is observationally stable (theoretically can undergo alpha decay with half-life over 5.5×10¹⁷ years), ¹⁵¹Eu was found in 2007 to be unstable and undergo alpha decay.^[4] The half-life is measured to be (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 10¹⁸ years^[5] which corresponds to 1 alpha decay per two minutes in every kilogram of natural europium. Besides the natural radioisotope ¹⁵¹Eu, 36 artificial radioisotopes have been characterized, with the most stable being ¹⁵⁰Eu with a half-life of 36.9 years, ¹⁵²Eu with a half-life of 13.516 years, ¹⁵⁴Eu with a half-life of 8.593 years, and ¹⁵⁵Eu with a half-life of 4.7612 years. The majority of the remaining radioactive isotopes, which range from ¹³⁰Eu to ¹⁷⁰Eu, have half-lives that are less than 12.2 seconds. This element also has 18 metastable isomers, with the most stable being ^150mEu (t_1/2 12.8 hours), ^152m1Eu (t_1/2 9.3116 hours) and ^152m5Eu (t_1/2 96 minutes).

The primary decay mode before the most abundant stable isotope, ¹⁵³Eu, is electron capture, and the primary mode after is beta decay. The primary decay products before ¹⁵³Eu are isotopes of samarium and the primary products after are isotopes of gadolinium.

^ 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.
^ "Standard Atomic Weights: Europium". CIAAW. 1995.
^ 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.
^ Belli, P.; et al. (2007). "Search for α decay of natural europium". Nuclear Physics A. 789 (1–4): 15–29. Bibcode:2007NuPhA.789...15B. doi:10.1016/j.nuclphysa.2007.03.001.
^ Casali, N.; Nagorny, S. S.; Orio, F.; Pattavina, L.; et al. (2014). "Discovery of the ¹⁵¹Eu α decay". Journal of Physics G: Nuclear and Particle Physics. 41 (7): 075101. arXiv:1311.2834. Bibcode:2014JPhG...41g5101C. doi:10.1088/0954-3899/41/7/075101. S2CID 116920467.

[NUBASE2020-1] 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] "Standard Atomic Weights: Europium". CIAAW. 1995.

[CIAAW2021-3] 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.

[151Eu-Belli-4] Belli, P.; et al. (2007). "Search for α decay of natural europium". Nuclear Physics A. 789 (1–4): 15–29. Bibcode:2007NuPhA.789...15B. doi:10.1016/j.nuclphysa.2007.03.001.

[154Eu--5] Casali, N.; Nagorny, S. S.; Orio, F.; Pattavina, L.; et al. (2014). "Discovery of the ¹⁵¹Eu α decay". Journal of Physics G: Nuclear and Particle Physics. 41 (7): 075101. arXiv:1311.2834. Bibcode:2014JPhG...41g5101C. doi:10.1088/0954-3899/41/7/075101. S2CID 116920467.

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