Isotopes of selenium

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.

Main isotopes of selenium (₃₄Se)

Iso­tope Decay 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 3.27×10^5 y β^− ^79Br ^80Se 49.80% stable ^82Se 8.82% 1.08×10^20 y β^−β^− ^82Kr
Standard atomic weight Ar, standard(Se)	78.971(8)[1]

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [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]	Natural abundance (mole fraction)
	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)×10^5 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)×10^20 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. # – 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. 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

Selenium-75

Radiopharmaceutical.

References

1. Meija, Juris; 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 Archived September 27, 2011, at the Wayback Machine
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.

• 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, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • 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. Lay summary.
• 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.