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

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 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. ⁸⁴Ge through ⁸⁷Ge also have minor β⁻ delayed neutron emission decay paths.

Relative atomic mass: 72.630(8)

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
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+
					2p	58Zn
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	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+
					β−	75As
75m2Ge	192.18(7) keV			216(5) ns			5/2+
76Ge	32	44	75.9214026(18)	1.78(8)×1021 y	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+#

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.
• Angular momentum or 3rd order sub particles are omitted as spin(2)=0,45,45.
• 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.
• Nuclide masses are given by IUPAP Commission on Symbols, Units, Nomenclature, Atomic Masses and Fundamental Constants (SUNAMCO).
• Isotope abundances are given by IUPAC Commission on Isotopic Abundances and Atomic Weights.

References

• Isotope masses from:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.

Isotopes of gallium	Isotopes of germanium	Isotopes of arsenic
Table of nuclides