Isotopes of germanium

Germanium (Ge) 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 ^[1] (130 million million times the age of the universe), giving it the distinction of being the nuclide with the longest directly measured half-life (tellurium-128 has a half-life > 1000 times longer, but it has been indirectly measured by decay products in ancient rocks).

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%.^[2] When bombarded with alpha particles, the isotopes ⁷²Ge and ⁷⁶Ge will generate stable ⁷⁵As and ⁷⁷Se, releasing high energy electrons in the process.^[3]

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 stable is ⁶⁰Ge with a half-life of 30 ms.

While most of germanium's radioisotopes decay by beta decay, ⁶¹Ge and ⁶⁴Ge decay by β⁺ delayed proton emission.^[2] ⁸⁴Ge through ⁸⁷Ge also have minor β^- delayed neutron emission decay paths.^[2]

Standard atomic mass: 72.64(1) u

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life^{[n 1]}	decay mode(s)^[4]^{[n 2]}	daughter isotope(s)^{[n 3]}	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
nuclide symbol	excitation energy			half-life^{[n 1]}	decay mode(s)^[4]^{[n 2]}	daughter isotope(s)^{[n 3]}	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
⁵⁸Ge	32	26	57.99101(34)#		2p	⁵⁶Zn	0+
⁵⁹Ge	32	27	58.98175(30)#		2p	⁵⁷Zn	7/2-#
⁶⁰Ge	32	28	59.97019(25)#	30# ms	β⁺	⁶⁰Ga	0+
⁶⁰Ge	32	28	59.97019(25)#	30# ms	2p	⁵⁸Zn	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 4]}	32	36	67.928094(7)	270.95(16) 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 5]}	32	44	75.9214026(18)	1.78(8)×10²¹ a^{[n 6]}	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+#

^ Bold for isotopes with half-lives longer than the age of the universe (nearly stable)
^ Abbreviations:
EC: Electron capture
IT: Isomeric transition
^ Bold for stable isotopes
^ Used to generate ⁶⁸Ga
^ Primordial radionuclide
^ Longest directly measured half-life of all known radioisotopes

Notes

Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

Isotope masses from:
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter, J. K. Böhlke, P. De Bièvre, H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683. http://www.iupac.org/publications/pac/75/6/0683/pdf/.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. http://iupac.org/publications/pac/78/11/2051/pdf/. Lay summary.
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
- National Nuclear Data Center. "NuDat 2.3 database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. Retrieved August 2007.
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0849304859.

^ 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". arXiv:hep-ex/0309016 [hep-ex].
^ ^a ^b ^c G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
^ 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
^ http://www.nucleonica.net/unc.aspx

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