Isotopes of selenium

Short description: Nuclides with atomic number of 34 but with different mass numbers

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 (34Se) 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 of 327,000 years,[2][3] and 82Se, which has a very long half-life (~1020 years, decaying via double beta decay to 82Kr) and for practical purposes can be considered to be stable. There are 23 other unstable isotopes that have been characterized, the longest-lived being 79Se with a half-life 327,000 years, 75Se with a half-life of 120 days, and 72Se with a half-life of 8.40 days. Of the other isotopes, 73Se has the longest half-life, 7.15 hours; most others have half-lives not exceeding 38 seconds.

## 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
65Se  | 34  | 31  | 64.96466(64)#  | <50 ms  | β+ (>99.9%)  | 65As  | 3/2−#  |  |
β+, p (<.1%)  | 64Ge
66Se  | 34  | 32  | 65.95521(32)#  | 33(12) ms  | β+ | 66As  | 0+  |  |
67Se  | 34  | 33  | 66.95009(21)#  | 133(11) ms  | β+ (99.5%)  | 67As  | 5/2−#  |  |
β+, p (.5%)  | 66Ge
68Se  | 34  | 34  | 67.94180(4)  | 35.5(7) s  | β+ | 68As  | 0+  |  |
69Se  | 34  | 35  | 68.93956(4)  | 27.4(2) s  | β+ (99.955%)  | 69As  | (1/2−)  |  |
β+, p (.045%)  | 68Ge
69m1Se  | 39.4(1) keV  | 2.0(2) μs  |  |  | 5/2−  |  |
69m2Se  | 573.9(10) keV  | 955(16) ns  |  |  | 9/2+  |  |
70Se  | 34  | 36  | 69.93339(7)  | 41.1(3) min  | β+ | 70As  | 0+  |  |
71Se  | 34  | 37  | 70.93224(3)  | 4.74(5) min  | β+ | 71As  | 5/2−  |  |
71m1Se  | 48.79(5) keV  | 5.6(7) μs  |  |  | 1/2− to 9/2−  |  |
71m2Se  | 260.48(10) keV  | 19.0(5) μs  |  |  | (9/2)+  |  |
72Se  | 34  | 38  | 71.927112(13)  | 8.40(8) d  | EC | 72As  | 0+  |  |
73Se  | 34  | 39  | 72.926765(11)  | 7.15(8) h  | β+ | 73As  | 9/2+  |  |
73mSe  | 25.71(4) keV  | 39.8(13) min  | IT  | 73Se  | 3/2−  |  |
β+ | 73As
74Se  | 34  | 40  | 73.9224764(18)  | Observationally Stable[n 9] | 0+  | 0.0089(4)  |
75Se  | 34  | 41  | 74.9225234(18)  | 119.779(4) d  | EC  | 75As | 5/2+  |  |
76Se  | 34  | 42  | 75.9192136(18)  | Stable | 0+  | 0.0937(29)  |
77Se  | 34  | 43  | 76.9199140(18)  | Stable | 1/2−  | 0.0763(16)  |
77mSe  | 161.9223(7) keV  | 17.36(5) s  | IT  | 77Se | 7/2+  |  |
78Se  | 34  | 44  | 77.9173091(18)  | Stable | 0+  | 0.2377(28)  |
79Se[n 10] | 34  | 45  | 78.9184991(18)  | 3.27(8)×105 y  | β− | 79Br | 7/2+  |  |
79mSe  | 95.77(3) keV  | 3.92(1) min  | IT (99.944%)  | 79Se  | 1/2−  |  |
β− (.056%)  | 79Br
80Se  | 34  | 46  | 79.9165213(21)  | Observationally Stable[n 11] | 0+  | 0.4961(41)  |
81Se  | 34  | 47  | 80.9179925(22)  | 18.45(12) min  | β− | 81Br | 1/2−  |  |
81mSe  | 102.99(6) keV  | 57.28(2) min  | IT (99.948%)  | 81Se  | 7/2+  |  |
β− (.052%)  | 81Br
82Se[n 12] | 34  | 48  | 81.9166994(22)  | 0.97(5)×1020 y | β−β− | 82Kr | 0+  | 0.0873(22)  |
83Se  | 34  | 49  | 82.919118(4)  | 22.3(3) min  | β− | 83Br  | 9/2+  |  |
83mSe  | 228.50(20) keV  | 70.1(4) s  | β− | 83Br  | 1/2−  |  |
84Se  | 34  | 50  | 83.918462(16)  | 3.1(1) min  | β− | 84Br  | 0+  |  |
85Se  | 34  | 51  | 84.92225(3)  | 31.7(9) s  | β− | 85Br  | (5/2+)#  |  |
86Se  | 34  | 52  | 85.924272(17)  | 15.3(9) s  | β− | 86Br  | 0+  |  |
87Se  | 34  | 53  | 86.92852(4)  | 5.50(12) s  | β− (99.64%)  | 87Br  | (5/2+)#  |  |
β−, n (.36%)  | 86Br
88Se  | 34  | 54  | 87.93142(5)  | 1.53(6) s  | β− (99.01%)  | 88Br  | 0+  |  |
β−, n (.99%)  | 87Br
89Se  | 34  | 55  | 88.93645(32)#  | 0.41(4) s  | β− (92.2%)  | 89Br  | (5/2+)#  |  |
β−, n (7.8%)  | 88Br
90Se  | 34  | 56  | 89.93996(43)#  | 300# ms [>300 ns]  | β−, n  | 89Br  | 0+  |  |
β− | 90Br
91Se  | 34  | 57  | 90.94596(54)#  | 270(50) ms  | β− (79%)  | 91Br  | 1/2+#  |  |
β−, n  | 90Br
92Se  | 34  | 58  | 91.94992(64)#  | 100# ms [>300 ns]  | β− | 92Br  | 0+  |  |
93Se  | 34  | 59  | 92.95629(86)#  | 50# ms [>300 ns]  |  |  | 1/2+#  |  |
94Se  | 34  | 60  | 93.96049(86)#  | 20# ms [>300 ns]  |  |  | 0+  |  |

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

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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. ↑ Believed to decay by β+β+ to 74Ge
10. ↑ Long-lived fission product
11. ↑ Believed to decay by β−β− to 80Kr
12. ↑ 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]

## 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. ↑ The half-life of 79Se
3. ↑ 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.
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): 10157. doi:10.1038/ncomms10157. ISSN 2041-1723. PMID 26679529. PMC 4703861. https://www.nature.com/articles/ncomms10157.
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:
* 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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Isotopes of the chemical elements

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* Table of nuclides
* Categories: Isotopes
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* Metastable isotopes
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