Isotopes of germanium

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).

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)

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]

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.

List of isotopes
Nuclide
[n 1]		 Z N Isotopic mass (Da)[6]
[n 2][n 3]		 Half-life[1]
[n 4][n 5]		 Decay
mode[1]
[n 6]		 Daughter
isotope
[n 7]		 Spin and
parity[1]
[n 8][n 5]		 Natural abundance (mole fraction)
Excitation energy Normal proportion[1] Range of variation
59Ge 32 27 58.98243(43)# 13.3(17) ms β+, p (93%) 58Zn 7/2−#
β+ (7%) 59Ga
2p? 57Zn
60Ge 32 28 59.97045(32)# 21(6) ms β+, p 59Zn 0+
β+, 2p? (<14%) 58Cu
61Ge 32 29 60.96373(32)# 40.7(4) ms β+, p (87%) 60Zn 3/2−#
β+ (18%) 61Ga
62Ge 32 30 61.95476(15)# 82.5(14) ms β+ 62Ga 0+
β+, p? 61Zn
63Ge 32 31 62.949628(40) 153.6(11) ms β+ 63Ga 3/2−#
β+, p? 62Zn
64Ge 32 32 63.9416899(40) 63.7(25) s β+ 64Ga 0+
65Ge 32 33 64.9393681(23) 30.9(5) s β+ (99.99%) 65Ga 3/2−
β+, p (0.011%) 64Zn
66Ge 32 34 65.9338621(26) 2.26(5) h β+ 66Ga 0+
67Ge 32 35 66.9327170(46) 18.9(3) min β+ 67Ga 1/2−
67m1Ge 18.20(5) keV 13.7(9) μs IT 67Ge 5/2−
67m2Ge 751.70(6) keV 109.1(38) ns IT 67Ge 9/2+
68Ge[n 9] 32 36 67.9280953(20) 271.05(8) d EC 68Ga 0+
69Ge 32 37 68.9279645(14) 39.05(10) h β+ 69Ga 5/2−
69m1Ge 86.76(2) keV 5.1(2) μs IT 69Ge 1/2−
69m2Ge 397.94(2) keV 2.81(5) μs IT 69Ge 9/2+
70Ge 32 38 69.92424854(88) Stable 0+ 0.2052(19)
71Ge 32 39 70.92495212(87) 11.43(3) d EC 71Ga 1/2−
71mGe 198.354(14) keV 20.41(18) ms IT 71Ge 9/2+
72Ge 32 40 71.922075824(81) Stable 0+ 0.2745(15)
72mGe 691.43(4) keV 444.2(8) ns IT 72Ge 0+
73Ge 32 41 72.923458954(61) Stable 9/2+ 0.0776(8)
73m1Ge 13.2845(15) keV 2.91(3) μs IT 73Ge 5/2+
73m2Ge 66.725(9) keV 499(11) ms IT 73Ge 1/2−
74Ge 32 42 73.921177760(13) Stable 0+ 0.3652(12)
75Ge 32 43 74.922858370(55) 82.78(4) min β− 75As 1/2−
75m1Ge 139.69(3) keV 47.7(5) s IT (99.97%) 75Ge 7/2+
β− (0.030%) 75As
75m2Ge 192.19(6) keV 216(5) ns IT 75Ge 5/2+
76Ge[n 10] 32 44 75 921402.725(19) (2.022±0.018±0.038)×1021 y[7] β−β− 76Se 0+ 0.0775(12)
77Ge 32 45 76 923549.843(56) 11.211(3) h β− 77As 7/2+
77mGe 159.71(6) keV 53.7(6) s β− (81%) 77As 1/2−
IT (19%) 77Ge
78Ge 32 46 77.9228529(38) 88.0(10) min β− 78As 0+
79Ge 32 47 78.925360(40) 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 79.9253508(22) 29.5(4) s β− 80As 0+
81Ge 32 49 80.9288329(22) 9(2) s β− 81As 9/2+#
81mGe 679.14(4) keV 6(2) s β− 81As (1/2+)
IT? (<1%) 81Ge
82Ge 32 50 81.9297740(24) 4.31(19) s β− 82As 0+
83Ge 32 51 82.9345391(26) 1.85(6) s β− 83As (5/2+)
β−, n? 82As
84Ge 32 52 83.9375751(34) 951(9) ms β− (89.4%) 84As 0+
β−, n (10.6%) 83As
85Ge 32 53 84.9429697(40) 495(5) ms β− (82.8%) 85As (3/2+,5/2+)#
β−, n (17.2%) 84As
β−, 2n? 83As
86Ge 32 54 85.94697(47) 221.6(11) ms β− (55%) 86As 0+
β−, n (45%) 85As
87Ge 32 55 86.95320(32)# 103(4) ms β− 87As 5/2+#
β−, n? 86As
β−, 2n? 85As
88Ge 32 56 87.95757(43)# 61(6) ms β− 88As 0+
β−, n? 87As
β−, 2n? 86As
89Ge 32 57 88.96453(43)# 60# ms [>300 ns] β−? 89As 3/2+#
β−, n? 88As
β−, 2n? 87As
90Ge 32 57 89.96944(54)# 30# ms [>400 ns] β−? 90As 0+
β−, n? 89As
β−, 2n? 88As
91Ge[8] 32 59
92Ge[8] 32 60
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. # – 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

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; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (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. 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. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  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. 131 (14). American Physical Society (APS): 142501. arXiv:2308.09795. Bibcode:2023PhRvL.131n2501A. doi:10.1103/physrevlett.131.142501. ISSN 0031-9007. PMID 37862664. S2CID 261049638.
  8. Shimizu, Y.; Kubo, T.; Sumikama, T.; Fukuda, N.; Takeda, H.; Suzuki, H.; Ahn, D. S.; Inabe, N.; Kusaka, K.; Ohtake, M.; Yanagisawa, Y.; Yoshida, K.; Ichikawa, Y.; Isobe, T.; Otsu, H.; Sato, H.; Sonoda, T.; Murai, D.; Iwasa, N.; Imai, N.; Hirayama, Y.; Jeong, S. C.; Kimura, S.; Miyatake, H.; Mukai, M.; Kim, D. G.; Kim, E.; Yagi, A. (8 April 2024). "Production of new neutron-rich isotopes near the N = 60 isotones Ge 92 and As 93 by in-flight fission of a 345 MeV/nucleon U 238 beam". Physical Review C. 109 (4). doi:10.1103/PhysRevC.109.044313.
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