Isotopes of erbium

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Naturally occurring erbium (Er) is composed of 6 stable isotopes, 162Er, 164Er, 166Er, 167Er, 168Er, and 170Er with 166Er being the most abundant (33.503% natural abundance). 30 radioisotopes have been characterized with between 74 and 109 neutrons, or 142 to 177 nucleons, with the most stable being 169Er with a half-life of 9.4 days, 172Er with a half-life of 49.3 hours, 160Er with a half-life of 28.58 hours, 165Er with a half-life of 10.36 hours, and 171Er with a half-life of 7.516 hours. All of the remaining radioactive isotopes have half-lives that are less than 3.5 hours, and the majority of these have half-lives that are less than 4 minutes. This element also has 13 meta states, with the most stable being 167mEr (t½ 2.269 seconds).

The isotopes of erbium range in atomic weight from 141.9723 u (142Er) to 176.9541 u (177Er). The primary decay mode before the most abundant stable isotope, 166Er, is electron capture, and the primary mode after is beta decay. The primary decay products before 166Er are holmium isotopes, and the primary products after are thulium isotopes.

Standard atomic mass: 167.259(3) u

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[1][n 1]
daughter
isotope(s)[n 2]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
142Er 68 74 141.97231(47)# 0+
143Er 68 75 142.96634(64)# 200# ms 9/2-#
144Er 68 76 143.96038(43)# 400# ms [>200 ns] β+ 144Ho 0+
145Er 68 77 144.95739(43)# 900(300) ms β+ 145Ho 1/2+#
β+, p (rare) 144Dy
146Er 68 78 145.95200(32)# 1.7(6) s β+ 146Ho 0+
β+, p 145Dy
147Er 68 79 146.94949(32)# ~2.5 s β+ 147Ho (1/2+)
β+, p 146Dy
147mEr 100(50)# keV 2.5(2) s β+ 147Ho (11/2-)
148Er 68 80 147.94455(21)# 4.6(2) s β+ (99.85%) 148Ho 0+
β+, p (.15%) 147Dy
149Er 68 81 148.94231(3) 4(2) s β+ (93%) 149Ho (1/2+)
β+, p (7%) 148Dy
149m1Er 741.8(2) keV 8.9(2) s β+ (96.5%) 149Ho (11/2-)
IT (3.5%) 149Er
β+, p (.18%) 148Dy
149m2Er 2611.1(3) keV 0.61(8) µs (19/2+)
149m3Er 3242.7+X keV 4.8(1) µs (27/2-)
150Er 68 82 149.937914(18) 18.5(7) s β+ 150Ho 0+
151Er 68 83 150.937449(18) 23.5(13) s β+ 151Ho (7/2-)
151m1Er 2585.5(6) keV 580(20) ms IT (95.3%) 151Er (27/2-)
β+ (4.7%) 151Ho
151m2Er 10286+X keV 0.42(5) µs (67/2,69/2,71/2)
152Er 68 84 151.935050(11) 10.3(1) s α (90%) 148Dy 0+
β+ (10%) 152Ho
153Er 68 85 152.935063(9) 37.1(2) s α (53%) 149Dy 7/2(-)
β+ (47%) 153Ho
154Er 68 86 153.932783(6) 3.73(9) min β+ (99.53%) 154Ho 0+
α (.47%) 150Dy
155Er 68 87 154.933209(7) 5.3(3) min β+ (99.98%) 155Ho 7/2-
α (.022%) 151Dy
156Er 68 88 155.931065(26) 19.5(10) min β+ 156Ho 0+
157Er 68 89 156.93192(3) 18.65(10) min β+ 157Ho 3/2-
157mEr 155.4(3) keV 76(6) ms IT 157Er (9/2+)
158Er 68 90 157.929893(27) 2.29(6) h EC 158Ho 0+
159Er 68 91 158.930684(5) 36(1) min β+ 159Ho 3/2-
159m1Er 182.602(24) keV 337(14) ns 9/2+
159m2Er 429.05(3) keV 590(60) ns 11/2-
160Er 68 92 159.929083(26) 28.58(9) h EC 160Ho 0+
161Er 68 93 160.929995(10) 3.21(3) h β+ 161Ho 3/2-
161mEr 396.44(4) keV 7.5(7) µs 11/2-
162Er 68 94 161.928778(4) Observationally Stable[n 3] 0+ 0.00139(5)
163Er 68 95 162.930033(6) 75.0(4) min β+ 163Ho 5/2-
163mEr 445.5(6) keV 580(100) ns (11/2-)
164Er 68 96 163.929200(3) Observationally Stable[n 4] 0+ 0.01601(3)
165Er 68 97 164.930726(3) 10.36(4) h EC 165Ho 5/2-
166Er 68 98 165.9302931(27) Observationally Stable[n 5] 0+ 0.33503(36)
167Er 68 99 166.9320482(27) Observationally Stable[n 6] 7/2+ 0.22869(9)
167mEr 207.801(5) keV 2.269(6) s IT 167Er 1/2-
168Er 68 100 167.9323702(27) Observationally Stable[n 7] 0+ 0.26978(18)
169Er 68 101 168.9345904(27) 9.392(18) d β- 169Tm 1/2-
170Er 68 102 169.9354643(30) Observationally Stable[n 8] 0+ 0.14910(36)
171Er 68 103 170.9380298(30) 7.516(2) h β- 171Tm 5/2-
171mEr 198.6(1) keV 210(10) ns 1/2-
172Er 68 104 171.939356(5) 49.3(3) h β- 172Tm 0+
173Er 68 105 172.94240(21)# 1.434(17) min β- 173Tm (7/2-)
174Er 68 106 173.94423(32)# 3.2(2) min β- 174Tm 0+
175Er 68 107 174.94777(43)# 1.2(3) min β- 175Tm (9/2+)
176Er 68 108 175.95008(43)# 20# s β- 176Tm 0+
177Er 68 109 176.95405(54)# 3# s β- 177Tm 1/2-#
  1. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  2. ^ Bold for stable isotopes
  3. ^ Believed to undergo α decay to 158Dy or β+β+ to 162Dy with a half-life over 140×1012 years
  4. ^ Believed to undergo α decay to 160Dy or β+β+ to 164Dy
  5. ^ Believed to undergo α decay to 162Dy
  6. ^ Believed to undergo α decay to 163Dy
  7. ^ Believed to undergo α decay to 164Dy
  8. ^ Believed to undergo α decay to 166Dy or β-β- to 170Yb with a half-life over 320×1015 years

References[edit]

  1. ^ http://www.nucleonica.net/unc.aspx


Isotopes of holmium Isotopes of erbium Isotopes of thulium
Table of nuclides