Isotopes of selenium

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The chemical element selenium (Se) has six naturally occurring isotopes, five of which 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,[1][2] and 82Se which has a very long half-life (~1020 yr, decaying via double beta decay to 82Kr) and for practical purposes can be considered to be stable. 23 other unstable isotopes 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.

Standard atomic mass: 78.96(3) u

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life[n 1] decay
mode(s)[3][n 2]
daughter
isotope(s)[n 3]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
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 4] 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 5] 34 45 78.9184991(18) 3.27(8)×105 a 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 6] 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 7] 34 48 81.9166994(22) 0.97(5)×1020 a 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%) 88Br
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. ^ Bold for isotopes with half-lives longer than the age of the universe (nearly stable)
  2. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  3. ^ Bold for stable isotopes
  4. ^ Believed to decay by β+β+ to 74Ge
  5. ^ Long-lived fission product
  6. ^ Believed to decay by β-β- to 80Kr
  7. ^ Primordial radionuclide

Notes[edit]

  • The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

See also[edit]

References[edit]

  1. ^ The half-life of 79Se
  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. 
  3. ^ http://www.nucleonica.net/unc.aspx


Isotopes of arsenic Isotopes of selenium Isotopes of bromine
Table of nuclides