Isotopes of erbium

Naturally occurring erbium (68Er) is composed of 6 stable isotopes, with 166Er being the most abundant (33.503% natural abundance). Thirty radioisotopes have been characterized with between 74 and 108 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 (t1/2 2.269 seconds).

Main isotopes of erbium (68Er)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
160Er syn 28.58 h ε 160Ho
162Er 0.139% stable
164Er 1.601% stable
165Er syn 10.36 h ε 165Ho
166Er 33.503% stable
167Er 22.869% stable
168Er 26.978% stable
169Er syn 9.4 d β 169Tm
170Er 14.910% stable
171Er syn 7.516 h β 171Tm
172Er syn 49.3 h β 172Tm
Standard atomic weight Ar, standard(Er)

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.

List of isotopes

Nuclide
[n 1]
Z N Isotopic mass (Da)
[n 2][n 3]
Half-life
[n 4]
Decay
mode

[n 5]
Daughter
isotope

[n 6]
Spin and
parity
[n 7][n 4]
Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion Range of variation
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 8] 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 9] 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 10] 0+ 0.33503(36)
167Er 68 99 166.9320482(27) Observationally Stable[n 11] 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 12] 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 13] 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. mEr  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. #  Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. Modes of decay:
    EC:Electron capture
    IT:Isomeric transition
    p:Proton emission
  6. Bold symbol as daughter  Daughter product is stable.
  7. () spin value  Indicates spin with weak assignment arguments.
  8. Believed to undergo α decay to 158Dy or β+β+ to 162Dy with a half-life over 140×1012 years
  9. Believed to undergo α decay to 160Dy or β+β+ to 164Dy
  10. Believed to undergo α decay to 162Dy
  11. Believed to undergo α decay to 163Dy
  12. Believed to undergo α decay to 164Dy
  13. Believed to undergo α decay to 166Dy or ββ to 170Yb with a half-life over 320×1015 years

Erbium-169

Radiopharmaceutical.

References

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