Isotopes of germanium (32Ge)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
68Ge synth 270.8 d ε 68Ga
70Ge 20.5% stable
71Ge synth 11.3 d ε 71Ga
72Ge 27.4% stable
73Ge 7.76% stable
74Ge 36.5% stable
76Ge 7.75% 1.78×1021 y β−β− 76Se
Standard atomic weight Ar°(Ge)
  • 72.630±0.008
  • 72.630±0.008 (abridged)[2][3]

Germanium (32Ge) has five naturally occurring isotopes, 70Ge, 72Ge, 73Ge, 74Ge, and 76Ge. Of these, 76Ge is very slightly radioactive, decaying by double beta decay with a half-life of 1.78 × 1021 years[4] (130 billion times the age of the universe).

Stable 74Ge is the most common isotope, having a natural abundance of approximately 36%. 76Ge is the least common with a natural abundance of approximately 7%.[5] When bombarded with alpha particles, the isotopes 72Ge and 76Ge will generate stable 75As and 77Se, releasing high energy electrons in the process.[6]

At least 27 radioisotopes have also been synthesized ranging in atomic mass from 58 to 89. The most stable of these is 68Ge, decaying by electron capture with a half-life of 270.95 d. It decays to the medically useful positron-emitting isotope 68Ga. (See gallium-68 generator for notes on the source of this isotope, and its medical use.) The least stable known germanium isotope is 59Ge with a half-life of 13.3 ms.

While most of germanium's radioisotopes decay by beta decay, 61Ge and 65Ge can also decay by β+-delayed proton emission.[5] 84Ge through 87Ge also have minor β−-delayed neutron emission decay paths.[5]

76Ge is used in experiments on the nature of neutrinos, by searching for neutrinoless double beta decay.

71Ge is the most stable nuclide for isotones with 39 neutrons, which has a half-life of 11.3 days. Note that 39 is the most "unstable" neutron number among the numbers 0 to 128 (compare: 87 is the most "unstable" proton number among the numbers 1 to 105), all other numbers (0 to 128) of neutrons have a nuclide with a half-life 22.2 years or more (including stable nuclides).

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
58Ge 32 26 57.99101(34)# 2p 56Zn 0+
59Ge 32 27 58.98175(30)# 13.3(17) ms 2p 57Zn 7/2−#
60Ge 32 28 59.97019(25)# 21(6) ms β+, p 59Zn 0+
β+, 2p 58Cu
61Ge 32 29 60.96379(32)# 39(12) ms β+, p (80%) 60Zn (3/2−)#
β+ (20%) 61Ga
62Ge 32 30 61.95465(15)# 129(35) ms β+ 62Ga 0+
63Ge 32 31 62.94964(21)# 142(8) ms β+ 63Ga (3/2−)#
64Ge 32 32 63.94165(3) 63.7(25) s β+ 64Ga 0+
65Ge 32 33 64.93944(11) 30.9(5) s β+ (99.99%) 65Ga (3/2)−
β+, p (.01%) 64Zn
66Ge 32 34 65.93384(3) 2.26(5) h β+ 66Ga 0+
67Ge 32 35 66.932734(5) 18.9(3) min β+ 67Ga 1/2−
67m1Ge 18.20(5) keV 13.7(9) μs 5/2−
67m2Ge 751.70(6) keV 110.9(14) ns 9/2+
68Ge[n 9] 32 36 67.928094(7) 271.05(8) d EC 68Ga 0+
69Ge 32 37 68.9279645(14) 39.05(10) h β+ 69Ga 5/2−
69m1Ge 86.765(14) keV 5.1(2) μs 1/2−
69m2Ge 397.944(18) keV 2.81(5) μs 9/2+
70Ge 32 38 69.9242474(11) Stable 0+ 0.2038(18)
71Ge 32 39 70.9249510(11) 11.43(3) d EC 71Ga 1/2−
71mGe 198.367(10) keV 20.40(17) ms IT 71Ge 9/2+
72Ge 32 40 71.9220758(18) Stable 0+ 0.2731(26)
72mGe 691.43(4) keV 444.2(8) ns 0+
73Ge 32 41 72.9234589(18) Stable 9/2+ 0.0776(8)
73m1Ge 13.2845(15) keV 2.92(3) μs 5/2+
73m2Ge 66.726(9) keV 499(11) ms 1/2−
74Ge 32 42 73.9211778(18) Stable 0+ 0.3672(15)
75Ge 32 43 74.9228589(18) 82.78(4) min β− 75As 1/2−
75m1Ge 139.69(3) keV 47.7(5) s IT (99.97%) 75Ge 7/2+
β− 75As
75m2Ge 192.18(7) keV 216(5) ns 5/2+
76Ge[n 10] 32 44 75.9214026(18) (2.022±0.018±0.038)×1021 y[7] β−β− 76Se 0+ 0.0783(7)
77Ge 32 45 76.9235486(18) 11.30(1) h β− 77As 7/2+
77mGe 159.70(10) keV 52.9(6) s β− (79%) 77As 1/2−
IT (21%) 77Ge
78Ge 32 46 77.922853(4) 88(1) min β− 78As 0+
79Ge 32 47 78.9254(1) 18.98(3) s β− 79As (1/2)−
79mGe 185.95(4) keV 39.0(10) s β− (96%) 79As (7/2+)#
IT (4%) 79Ge
80Ge 32 48 79.92537(3) 29.5(4) s β− 80As 0+
81Ge 32 49 80.92882(13) 7.6(6) s β− 81As 9/2+#
81mGe 679.13(4) keV 7.6(6) s β− (99%) 81As (1/2+)
IT (1%) 81Ge
82Ge 32 50 81.92955(26) 4.55(5) s β− 82As 0+
83Ge 32 51 82.93462(21)# 1.85(6) s β− 83As (5/2+)#
84Ge 32 52 83.93747(32)# 0.947(11) s β− (89.2%) 84As 0+
β−, n (10.8%) 83As
85Ge 32 53 84.94303(43)# 535(47) ms β− (86%) 85As 5/2+#
β−, n (14%) 84As
86Ge 32 54 85.94649(54)# >150 ns β−, n 85As 0+
β− 86As
87Ge 32 55 86.95251(54)# 0.14# s 5/2+#
88Ge 32 56 87.95691(75)# >=300 ns 0+
89Ge 32 57 88.96383(97)# >150 ns 3/2+#
This table header & footer:
  1. ↑ mGe – 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. 1 2 # – 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. ↑ Used to generate 68Ga
  10. ↑ Primordial radionuclide
  • Angular momentum or 3rd order sub particles are omitted as spin(2)=0,45,45.

References

  1. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ↑ "Standard Atomic Weights: Germanium". CIAAW. 2009.
  3. ↑ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; et al. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ↑ A. M. Bakalyarov; A. Ya. Balysh; S. T. Belyaev; V. I. Lebedev; S. V. Zhukov (2003). "Results of the experiment on investigation of Germanium-76 double beta decay". Physics of Particles and Nuclei Letters. 2 (2): 77–81. arXiv:hep-ex/0309016. Bibcode:2003hep.ex....9016B.
  5. 1 2 3 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
  6. ↑ Via a set of two reactions:
    4He + 72Ge → 75Se + 1n, 75Se decays by electron capture to 75As with a half-life of 120 days
    76Ge + 1n → 77Ge, which then undergoes beta decay to 77As with a half-life of 11.3 hours, which in turn undergoes beta decay to 77Se with a half-life of 39 hours
  7. ↑ M. Agostini; et al. (2023-10-03). "Final Results of GERDA on the Two-Neutrino Double-β Decay Half-Life of 76Ge". Physical Review Letters. American Physical Society (APS). 131 (14): 142501. arXiv:2308.09795. Bibcode:2023PhRvL.131n2501A. doi:10.1103/physrevlett.131.142501. ISSN 0031-9007. PMID 37862664. S2CID 261049638.
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