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 11.468 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)
	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]

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.

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 (<0.2%)	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+
63Ge	32	31	62.949628(40)	153.6(11) ms	β+	63Ga	3/2−#
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)	11.468(8) d[7]	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	75.921402725(19)	(2.022±0.018±0.038)×1021 y[8]	β−β−	76Se	0+	0.0775(12)
77Ge	32	45	76.923549843(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+)
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
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+#
88Ge	32	56	87.95757(43)#	61(6) ms	β−	88As	0+
89Ge	32	57	88.96453(43)#	60# ms [>300 ns]			3/2+#
90Ge	32	58	89.96944(54)#	30# ms [>400 ns]			0+
91Ge[9]	32	59
92Ge[9]	32	60
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