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% 1.78×10^21 y β^−β^− ^76Se
Standard atomic weight Ar°(Ge)
	72.630±0.008^[2] 72.630±0.008 (abridged)^[3]
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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] 84}Ge 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)×10^21 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: view

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

• Angular momentum or 3rd order sub particles are omitted as spin(2)=0,45,45.

References

• Isotope masses from:
  • 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
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
• "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
• Half-life, spin, and isomer data selected from the following sources.
  • 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
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

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. 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. 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.