Isotopes of germanium (₃₂Ge)

Main isotopes^[1]			Decay
	abundance	half-life (t_1/2)	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 A_r°(Ge)

72.630±0.008^[2]
72.630±0.008 (abridged)^[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)
Nuclide ^{[n 1]}	Excitation energy			Half-life ^{[n 4]}^{[n 5]}	Decay mode ^{[n 6]}	Daughter isotope ^{[n 7]}	Spin and parity ^{[n 8]}^{[n 5]}	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+
⁶⁰Ge	32	28	59.97019(25)#	21(6) ms	β⁺, 2p	⁵⁸Cu	0+
⁶¹Ge	32	29	60.96379(32)#	39(12) ms	β⁺, p (80%)	⁶⁰Zn	(3/2−)#
⁶¹Ge	32	29	60.96379(32)#	39(12) ms	β⁺ (20%)	⁶¹Ga	(3/2−)#
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)−
⁶⁵Ge	32	33	64.93944(11)	30.9(5) s	β⁺, p (.01%)	⁶⁴Zn	(3/2)−
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+
^75m1Ge	139.69(3) keV			47.7(5) s	β⁻	⁷⁵As	7/2+
^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−
^77mGe	159.70(10) keV			52.9(6) s	IT (21%)	⁷⁷Ge	1/2−
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+)#
^79mGe	185.95(4) keV			39.0(10) s	IT (4%)	⁷⁹Ge	(7/2+)#
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+)
^81mGe	679.13(4) keV			7.6(6) s	IT (1%)	⁸¹Ge	(1/2+)
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+
⁸⁴Ge	32	52	83.93747(32)#	0.947(11) s	β⁻, n (10.8%)	⁸³As	0+
⁸⁵Ge	32	53	84.94303(43)#	535(47) ms	β⁻ (86%)	⁸⁵As	5/2+#
⁸⁵Ge	32	53	84.94303(43)#	535(47) ms	β⁻, n (14%)	⁸⁴As	5/2+#
⁸⁶Ge	32	54	85.94649(54)#	>150 ns	β⁻, n	⁸⁵As	0+
⁸⁶Ge	32	54	85.94649(54)#	>150 ns	β⁻	⁸⁶As	0+
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

^ ^mGe – Excited nuclear isomer.
^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^ Bold half-life – nearly stable, half-life longer than age of universe.
^ ^a ^b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Modes of decay:

EC: Electron capture

IT: Isomeric transition

n: Neutron emission

p: Proton emission
^ Bold symbol as daughter – Daughter product is stable.
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ Used to generate ⁶⁸Ga
^ 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.

^ 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.
^ "Standard Atomic Weights: Germanium". CIAAW. 2009.
^ 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.
^ 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.
^ ^a ^b ^c 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
^ 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
^ 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.

EC:	Electron capture
IT:	Isomeric transition
n:	Neutron emission
p:	Proton emission