Isotopes of selenium

Main isotopes of Chemistry:selenium (34Se) | Iso­tope | Decay

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| abun­dance | half-life (t1/2) | mode | pro­duct
72Se  | syn | 8.4 d  | ε | 72As
γ | –
74Se  | 0.86%  | stable
75Se  | syn  | 119.8 d  | ε  | 75As
γ  | –
76Se  | 9.23%  | stable
77Se  | 7.60%  | stable
78Se  | 23.69%  | stable
79Se  | trace | 3.27×105 y  | β− | 79Br
80Se  | 49.80%  | stable
82Se  | 8.82%  | 1.08×1020 y  | β−β− | 82Kr
Standard atomic weight Ar, standard(Se)|

* 78.971(8)[1]

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Selenium has six natural isotopes that occur in significant quantities, along with the trace isotope 79Se, which occurs in minute quantities in uranium ores. Five of these isotopes are stable: 74Se, 76Se, 77Se, 78Se, and 80Se. The last three also occur as fission products, along with 79Se, which has a half-life about 330,000 years,[2] and 82Se, which has the very long half-life of 8.76×1019 years as it decays via double beta decay to krypton-82 and for practical purposes can be considered to be stable. There are 23 other unstable isotopes that have been characterized, the longest-lived after 79Se being 75Se with its half-life 119.78 days, 72Se at 8.40 days, and 73Se at 7.15 hours. The others are all under an hour and most do not exceed 38 seconds.

## Contents

* 1 List of isotopes
* 2 Use of radioisotopes
* 3 See also
* 4 References

## List of isotopes

Nuclide
[n 1] | Z | N | Isotopic mass (u)
[n 2][n 3] | Half-life
[n 4][n 5] | Decay
mode
[n 6] | Daughter
isotope
[n 7] | Spin and
parity
[n 8][n 5] | Physics:Natural abundance (mole fraction)

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Excitation energy  | Normal proportion  | Range of variation
63Se  | 34  | 29  | 62.98191(54)#  | 2016 | 13.2(39) ms  | β+, p (89%)  | 62Ge  | 3/2−#  |  |
β+ (11%)  | 63As
2p? (<0.5%)  | 61Ge
64Se  | 34  | 30  | 63.97117(54)#  | 2005 | 22.6(2) ms  | β+?  | 64As  | 0+  |  |
β+, p?  | 63Ge
65Se  | 34  | 31  | 64.96455(32)#  | 1993 | 34.2(7) ms  | β+, p (87%)  | 64Ge  | 3/2−#  |  |
β+ (13%)  | 65As
66Se  | 34  | 32  | 65.95528(22)#  | 1993 | 54(4) ms  | β+ | 66As  | 0+  |  |
β+, p?  | 65Ge
67Se  | 34  | 33  | 66.949994(72)  | 1991 | 133(4) ms  | β+ (99.5%)  | 67As  | 5/2−#  |  |
β+, p (0.5%)  | 66Ge
68Se  | 34  | 34  | 67.94182524(53)  | 1990 | 35.5(7) s  | β+ | 68As  | 0+  |  |
69Se  | 34  | 35  | 68.9394148(16)  | 1974 | 27.4(2) s  | β+ (99.95%)  | 69As  | 1/2−  |  |
β+, p (.052%)  | 68Ge
69m1Se  | 38.85(22) keV  | 1988 | 2.0(2) μs  | IT  | 69Se  | 5/2−  |  |
69m2Se  | 574.0(4) keV  | 1988 | 955(16) ns  | IT  | 69Se  | 9/2+  |  |
70Se  | 34  | 36  | 69.9335155(17)  | 1950 | 41.1(3) min  | β+ | 70As  | 0+  |  |
71Se  | 34  | 37  | 70.9322094(30)  | 1957 | 4.74(5) min  | β+ | 71As  | (5/2−)  |  |
71m1Se  | 48.79(5) keV  | 1982 | 5.6(7) μs  | IT  | 71Se  | (1/2−)  |  |
71m2Se  | 260.48(10) keV  | 1982 | 19.0(5) μs  | IT  | 71Se  | (9/2+)  |  |
72Se  | 34  | 38  | 71.9271405(21)  | 1948 | 8.40(8) d  | EC | 72As  | 0+  |  |
73Se  | 34  | 39  | 72.9267549(80)  | 1948 | 7.15(9) h  | β+ | 73As  | 9/2+  |  |
73mSe  | 25.71(4) keV  | 1953 | 39.8(17) min  | IT (72.6%)  | 73Se  | 3/2−  |  |
β+ (27.4%)  | 73As
74Se  | 34  | 40  | 73.922475933(15)  | 1922 | Observationally Stable[n 9] | 0+  | 0.0086(3)  |
75Se  | 34  | 41  | 74.922522870(78)  | 1947 | 119.78(3) d  | EC  | 75As | 5/2+  |  |
76Se  | 34  | 42  | 75.919213702(17)  | 1922 | Stable | 0+  | 0.0923(7)  |
77Se[n 10] | 34  | 43  | 76.919914150(67)  | 1922 | Stable | 1/2−  | 0.0760(7)  |
77mSe  | 161.9223(10) keV  | 1947 | 17.36(5) s  | IT  | 77Se | 7/2+  |  |
78Se[n 10] | 34  | 44  | 77.91730924(19)  | 1922 | Stable | 0+  | 0.2369 (22)  |
79Se[n 11] | 34  | 45  | 78.91849925(24)  | 1950 | 3.27(28)×105 y  | β− | 79Br | 7/2+  |  |
79mSe  | 95.77(3) keV  | 1950 | 3.900(18) min  | IT (99.94%)  | 79Se  | 1/2−  |  |
β− (0.056%)  | 79Br
80Se[n 10] | 34  | 46  | 79.9165218(10)  | 1922 | Observationally Stable[n 12] | 0+  | 0.4980(36)  |
81Se[n 10] | 34  | 47  | 80.9179930(10)  | 1949 | 18.45(12) min  | β− | 81Br | 1/2−  |  |
81mSe[n 10] | 103.00(6) keV  | 1949 | 57.28(2) min  | IT (99.95%)  | 81Se  | 7/2+  |  |
β− (0.051%)  | 81Br
82Se[n 10][n 13] | 34  | 48  | 81.91669953(50)  | 1922 | 8.76(15)×1019 y | β−β− | 82Kr | 0+  | 0.0882(15)  |
83Se  | 34  | 49  | 82.9191186(33)  | 1937 | 22.25(4) min  | β− | 83Br  | 9/2+  |  |
83mSe  | 228.92(7) keV  | 1947 | 70.1(4) s  | β− | 83Br  | 1/2−  |  |
84Se  | 34  | 50  | 83.9184668(21)  | 1960 | 3.26(10) min  | β− | 84Br  | 0+  |  |
85Se  | 34  | 51  | 84.9222608(28)  | 1960 | 32.9(3) s  | β− | 85Br  | (5/2)+  |  |
86Se  | 34  | 52  | 85.9243117(27)  | 1973 | 14.3(3) s  | β− | 86Br  | 0+  |  |
β−, n?  | 85Br
87Se  | 34  | 53  | 86.9286886(24)  | 1968 | 5.50(6) s  | β− (99.50%)  | 87Br  | (3/2+)  |  |
β−, n (0.60%)  | 86Br
88Se  | 34  | 54  | 87.9314175(36)  | 1970 | 1.53(6) s  | β− (99.01%)  | 88Br  | 0+  |  |
β−, n (0.99%)  | 87Br
89Se  | 34  | 55  | 88.9366691(40)  | 1971 | 430(50) ms  | β− (92.2%)  | 89Br  | 5/2+#  |  |
β−, n (7.8%)  | 88Br
90Se  | 34  | 56  | 89.94010(35)  | 1994 | 210(80) ms  | β− | 90Br  | 0+  |  |
β−, n?  | 89Br
91Se  | 34  | 57  | 90.94570(47)  | 1975 | 270(50) ms  | β− (79%)  | 91Br  | 1/2+#  |  |
β−, n (21%)  | 90Br
β−, 2n?  | 89Br
92Se  | 34  | 58  | 91.94984(43)#  | 1997 | 90# ms [>300 ns]  | β−?  | 92Br  | 0+  |  |
β−, n?  | 91Br
β−, 2n?  | 90Br
92mSe  | 3072(2) keV  | 2012 | 15.7(7) μs  | IT  | 92Se  | (9−)  |  |
93Se  | 34  | 59  | 92.95614(43)#  | 1997 | 130# ms [>300 ns]  | β−?  | 93Br  | 1/2+#  |  |
β−, n?  | 92Br
β−, 2n?  | 91Br
93mSe  | 678.2(7) keV  | 2012 | 420(100) ns  | IT  | 93Se  |  |  |
94Se  | 34  | 60  | 93.96049(54)#  | 1997 | 50# ms [>300 ns]  | β−?  | 94Br  | 0+  |  |
β−, n?  | 93Br
β−, 2n?  | 92Br
94mSe  | 2430.0(6) keV  | 2020 | 680(50) ns  | IT  | 94Se  | (7−)  |  |
95Se  | 34  | 61  | 94.96730(54)#  | 2010 | 70# ms [>400 ns]  | β−?  | 95Br  | 3/2+#  |  |
β−, n?  | 94Br
β−, 2n?  | 93Br
96Se[3] | 34  | 62  |  | 2024 |  |  |  |  |  |
97Se[3] | 34  | 63  |  | 2024 |  |  |  |  |  |

1. ↑ mSe - 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. ↑ Bold half-life - nearly stable, half-life longer than age of universe.
5. ↑ 5.0 5.1 # - Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
6. ↑ Modes of decay:  EC: | Electron capture

|

IT: | Isomeric transition
n: | Neutron emission
p: | Proton emission
7. ↑ Bold symbol as daughter - Daughter product is stable.
8. ↑ ( ) spin value - Indicates spin with weak assignment arguments.
9. ↑ Theoretically capable of β+β+ decay to 74Ge; half-life is above 2.3×1018 y.
10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 Fission product
11. ↑ Long-lived fission product
12. ↑ Theoretically capable of β−β− decay to 80Kr
13. ↑ Primordial radionuclide

## Use of radioisotopes

The isotope selenium-75 has radiopharmaceutical uses. For example, it is used in high-dose-rate endorectal brachytherapy, as an alternative to iridium-192.[4]

In paleobiogeochemistry, the ratio in amount of selenium-82 to selenium-76 (i.e, the value of δ82/76Se) can be used to track down the redox conditions on Earth during the Neoproterozoic era in order to gain a deeper understanding of the rapid oxygenation that trigger the emergence of complex organisms.[5][6]

## See also

Daughter products other than selenium

* Isotopes of krypton
* Isotopes of bromine
* Isotopes of arsenic
* Isotopes of germanium

## References

1. ↑ Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265–91. doi:10.1515/pac-2015-0305.
2. ↑ Jorg, Gerhard; Buhnemann, Rolf; Hollas, Simon; Kivel, Niko; Kossert, Karsten; Van Winckel, Stefaan; Gostomski, Christoph Lierse v. (2010). "Preparation of radiochemically pure 79Se and highly precise determination of its half-life". Applied Radiation and Isotopes 68 (12): 2339–51. doi:10.1016/j.apradiso.2010.05.006. PMID 20627600. Bibcode: 2010AppRI..68.2339J.
3. ↑ 3.0 3.1 Shimizu, Y.; Kubo, T.; Sumikama, T.; Fukuda, N.; Takeda, H.; Suzuki, H.; Ahn, D. S.; Inabe, N. et al. (8 April 2024). "Production of new neutron-rich isotopes near the N = 60 isotones Ge 92 and As 93 by in-flight fission of a 345 MeV/nucleon U 238 beam". Physical Review C 109 (4). doi:10.1103/PhysRevC.109.044313.
4. ↑ Shoemaker T; Vuong T; Glickman H; Kaifi S; Famulari G; Enger SA (2019). "Dosimetric Considerations for Ytterbium-169, Selenium-75, and Iridium-192 Radioisotopes in High-Dose-Rate Endorectal Brachytherapy". Int J Radiat Oncol Biol Phys 105 (4): 875–883. doi:10.1016/j.ijrobp.2019.07.003. PMID 31330175.
5. ↑ Pogge von Strandmann, Philip A. E.; Stüeken, Eva E.; Elliott, Tim; Poulton, Simon W.; Dehler, Carol M.; Canfield, Don E.; Catling, David C. (2015-12-18). "Selenium isotope evidence for progressive oxidation of the Neoproterozoic biosphere" (in en). Nature Communications 6 (1). doi:10.1038/ncomms10157. ISSN 2041-1723. PMID 26679529. Bibcode: 2015NatCo...610157P.
6. ↑ Stüeken, Eva E.. "Selenium isotopes as a biogeochemical proxy in deep time". https://core.ac.uk/download/pdf/161931618.pdf.

* Isotope masses from:
* Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A 729: 3–128, doi:10.1016/j.nuclphysa.2003.11.001, Bibcode: 2003NuPhA.729....3A, https://hal.archives-ouvertes.fr/in2p3-00020241/document
* Isotopic compositions and standard atomic masses from:
* Template:CIAAW2003
* Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051.
* 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, doi:10.1016/j.nuclphysa.2003.11.001, Bibcode: 2003NuPhA.729....3A, https://hal.archives-ouvertes.fr/in2p3-00020241/document
* National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/.
* Lide, David R., ed (2004). "11. Table of the Isotopes". CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

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