Isotopes of europium

Naturally occurring europium (Eu) is composed of 2 isotopes, ¹⁵¹Eu and ¹⁵³Eu, with ¹⁵³Eu being the most abundant (52.2% natural abundance). While ¹⁵³Eu is stable, ¹⁵¹Eu was recently found to be unstable and to undergo alpha decay with half-life of (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 10¹⁸ y.^[1] Besides natural radioisotope ¹⁵¹Eu, 36 artificial radioisotopes have been characterized, with the most stable being ¹⁵⁰Eu with a half-life of 36.9 years, ¹⁵²Eu with a half-life of 13.516 years, and ¹⁵⁴Eu with a half-life of 8.593 years. All of the remaining radioactive isotopes have half-lives that are less than 4.7612 years, and the majority of these have half-lives that are less than 12.2 seconds. This element also has 17 meta states, with the most stable being ^150mEu (t_1/2 12.8 hours), ^152m1Eu (t_1/2 9.3116 hours) and ^152m2Eu (t_1/2 96 minutes).

The primary decay mode before the most abundant stable isotope, ¹⁵³Eu, is electron capture, and the primary mode after is beta decay. The primary decay products before ¹⁵³Eu are isotopes of samarium and the primary products after are isotopes of gadolinium.

Relative atomic mass: 151.964(1).

Europium-155

Medium-lived
fission products
Prop: Unit:	t_½ (a)	Yield (%)	Q * (keV)	βγ *
¹⁵⁵Eu	4.76	0.0803	252	βγ
⁸⁵Kr	10.76	0.2180	687	βγ
^113mCd	14.1	0.0008	316	β
⁹⁰Sr	28.9	4.505	2826	β
¹³⁷Cs	30.23	6.337	1176	βγ
^121mSn	43.9	0.00005	390	βγ
¹⁵¹Sm	96.6	0.5314	77	β

Europium-155 is a fission product with a half-life of 4.76 years. It has a maximum decay energy of 252 KeV. In a thermal reactor (almost all current nuclear power plants), it has a low fission product yield, about half of one percent as much as the most abundant fission products.

¹⁵⁵Eu's large neutron capture cross section (about 3900 barns for thermal neutrons, 16000 resonance integral) means that most of even the small amount produced is destroyed in the course of the nuclear fuel's burnup. Yield, decay energy, and halflife are all far less than ¹³⁷Cs and ⁹⁰Sr, so ¹⁵⁵Eu is not a significant contributor to nuclear waste.

Some ¹⁵⁵Eu is also produced by successive neutron capture on ¹⁵³Eu (nonradioactive, 350 barns thermal, 1500 resonance integral, yield is about 5 times as great as ¹⁵⁵Eu) and ¹⁵⁴Eu (half-life 8.6 years, 1400 barns thermal, 1600 resonance integral, fission yield is extremely small because beta decay stops at ¹⁵⁴Sm); however the differing cross sections mean that both ¹⁵⁵Eu and ¹⁵⁴Eu are destroyed faster than they are produced.

¹⁵⁴Eu is a prolific emitter of gamma radiation.^[2]

Isotope	Halflife	Relative yield	Thermal neutron	Resonance integral
Eu-153	Stable	5	350	1500
Eu-154	8.6 years	Nearly 0	1500	1600
Eu-155	4.76 years	1	3900	16000

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life^{[n 1]}	decay mode(s)^[3]^{[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)^[3]^{[n 2]}	daughter isotope(s)^{[n 3]}	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
¹³⁰Eu	63	67	129.96357(54)#	1.1(5) ms [0.9(+5−3) ms]			2+#
¹³¹Eu	63	68	130.95775(43)#	17.8(19) ms			3/2+
¹³²Eu	63	69	131.95437(43)#	100# ms	β⁺	¹³²Sm
¹³²Eu	63	69	131.95437(43)#	100# ms	p	¹³¹Sm
¹³³Eu	63	70	132.94924(32)#	200# ms	β⁺	¹³³Sm	11/2−#
¹³⁴Eu	63	71	133.94651(21)#	0.5(2) s	β⁺	¹³⁴Sm
¹³⁴Eu	63	71	133.94651(21)#	0.5(2) s	β⁺, p (rare)	¹³³Pm
¹³⁵Eu	63	72	134.94182(32)#	1.5(2) s	β⁺	¹³⁵Sm	11/2−#
¹³⁵Eu	63	72	134.94182(32)#	1.5(2) s	β⁺, p	¹³⁴Pm	11/2−#
¹³⁶Eu	63	73	135.93960(21)#	3.3(3) s	β⁺ (99.91%)	¹³⁶Sm	(7+)
¹³⁶Eu	63	73	135.93960(21)#	3.3(3) s	β⁺, p (.09%)	¹³⁵Pm	(7+)
^136mEu	0(500)# keV			3.8(3) s	β⁺ (99.91%)	¹³⁶Sm	(3+)
^136mEu	0(500)# keV			3.8(3) s	β⁺, p (.09%)	¹³⁵Pm	(3+)
¹³⁷Eu	63	74	136.93557(21)#	8.4(5) s	β⁺	¹³⁷Sm	11/2−#
¹³⁸Eu	63	75	137.93371(3)	12.1(6) s	β⁺	¹³⁸Sm	(6−)
¹³⁹Eu	63	76	138.929792(14)	17.9(6) s	β⁺	¹³⁹Sm	(11/2)−
¹⁴⁰Eu	63	77	139.92809(6)	1.51(2) s	β⁺	¹⁴⁰Sm	1+
^140mEu	210(15) keV			125(2) ms	IT (99%)	¹⁴⁰Eu	5−#
^140mEu	210(15) keV			125(2) ms	β⁺(1%)	¹⁴⁰Sm	5−#
¹⁴¹Eu	63	78	140.924931(14)	40.7(7) s	β⁺	¹⁴¹Sm	5/2+
^141mEu	96.45(7) keV			2.7(3) s	IT (86%)	¹⁴¹Eu	11/2−
^141mEu	96.45(7) keV			2.7(3) s	β⁺ (14%)	¹⁴¹Sm	11/2−
¹⁴²Eu	63	79	141.92343(3)	2.36(10) s	β⁺	¹⁴²Sm	1+
^142mEu	460(30) keV			1.223(8) min	β⁺	¹⁴²Sm	8−
¹⁴³Eu	63	80	142.920298(12)	2.59(2) min	β⁺	¹⁴³Sm	5/2+
^143mEu	389.51(4) keV			50.0(5) µs			11/2−
¹⁴⁴Eu	63	81	143.918817(12)	10.2(1) s	β⁺	¹⁴⁴Sm	1+
^144mEu	1127.6(6) keV			1.0(1) µs			(8−)
¹⁴⁵Eu	63	82	144.916265(4)	5.93(4) d	β⁺	¹⁴⁵Sm	5/2+
^145mEu	716.0(3) keV			490 ns			11/2−
¹⁴⁶Eu	63	83	145.917206(7)	4.61(3) d	β⁺	¹⁴⁶Sm	4−
^146mEu	666.37(16) keV			235(3) µs			9+
¹⁴⁷Eu	63	84	146.916746(3)	24.1(6) d	β⁺ (99.99%)	¹⁴⁷Sm	5/2+
¹⁴⁷Eu	63	84	146.916746(3)	24.1(6) d	α (.0022%)	¹⁴³Pm	5/2+
¹⁴⁸Eu	63	85	147.918086(11)	54.5(5) d	β⁺ (100%)	¹⁴⁸Sm	5−
¹⁴⁸Eu	63	85	147.918086(11)	54.5(5) d	α (9.39×10⁻⁷%)	¹⁴⁴Pm	5−
¹⁴⁹Eu	63	86	148.917931(5)	93.1(4) d	EC	¹⁴⁹Sm	5/2+
¹⁵⁰Eu	63	87	149.919702(7)	36.9(9) y	β⁺	¹⁵⁰Sm	5(−)
^150mEu	42.1(5) keV			12.8(1) h	β⁻ (89%)	¹⁵⁰Gd	0−
					β⁺ (11%)	¹⁵⁰Sm
					IT (5×10⁻⁸%)	¹⁵⁰Eu
¹⁵¹Eu^{[n 4]}	63	88	150.9198502(26)	4.62×10¹⁸ y	α	¹⁴⁷Pm	5/2+	0.4781(6)
^151mEu	196.245(10) keV			58.9(5) µs			11/2−
¹⁵²Eu	63	89	151.9217445(26)	13.537(6) y	EC (72.09%), β⁺ (0.027%)	¹⁵²Sm	3−
¹⁵²Eu	63	89	151.9217445(26)	13.537(6) y	β⁻ (27.9%)	¹⁵²Gd	3−
^152m1Eu	45.5998(4) keV			9.3116(13) h	β⁻ (72%)	¹⁵²Gd	0−
^152m1Eu	45.5998(4) keV			9.3116(13) h	β⁺ (28%)	¹⁵²Sm	0−
^152m2Eu	65.2969(4) keV			0.94(8) µs			1−
^152m3Eu	78.2331(4) keV			165(10) ns			1+
^152m4Eu	89.8496(4) keV			384(10) ns			4+
^152m5Eu	147.86(10) keV			96(1) min			8−
¹⁵³Eu^{[n 5]}	63	90	152.9212303(26)	Observationally Stable^{[n 6]}			5/2+	0.5219(6)
¹⁵⁴Eu^{[n 5]}	63	91	153.9229792(26)	8.593(4) y	β⁻ (99.98%)	¹⁵⁴Gd	3−
¹⁵⁴Eu^{[n 5]}	63	91	153.9229792(26)	8.593(4) y	EC (.02%)	¹⁵⁴Sm	3−
^154m1Eu	145.3(3) keV			46.3(4) min	IT	¹⁵⁴Eu	(8−)
^154m2Eu	68.1702(4) keV			2.2(1) µs			2+
¹⁵⁵Eu^{[n 5]}	63	92	154.9228933(27)	4.7611(13) y	β⁻	¹⁵⁵Gd	5/2+
¹⁵⁶Eu^{[n 5]}	63	93	155.924752(6)	15.19(8) d	β⁻	¹⁵⁶Gd	0+
¹⁵⁷Eu	63	94	156.925424(6)	15.18(3) h	β⁻	¹⁵⁷Gd	5/2+
¹⁵⁸Eu	63	95	157.92785(8)	45.9(2) min	β⁻	¹⁵⁸Gd	(1−)
¹⁵⁹Eu	63	96	158.929089(8)	18.1(1) min	β⁻	¹⁵⁹Gd	5/2+
¹⁶⁰Eu	63	97	159.93197(22)#	38(4) s	β⁻	¹⁶⁰Gd	1(−)
¹⁶¹Eu	63	98	160.93368(32)#	26(3) s	β⁻	¹⁶¹Gd	5/2+#
¹⁶²Eu	63	99	161.93704(32)#	10.6(10) s	β⁻	¹⁶²Gd
¹⁶³Eu	63	100	162.93921(54)#	6# s	β⁻	¹⁶³Gd	5/2+#
¹⁶⁴Eu	63	101	163.94299(64)#	2# s	β⁻	¹⁶⁴Gd
¹⁶⁵Eu	63	102	164.94572(75)#	1# s	β⁻	¹⁶⁵Gd	5/2+#
¹⁶⁶Eu	63	103	165.94997(86)#	400# ms	β⁻	¹⁶⁶Gd
¹⁶⁷Eu	63	104	166.95321(86)#	200# ms	β⁻	¹⁶⁷Gd	5/2+#

↑ 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, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
↑ primordial radionuclide
↑ ^5.0 ^5.1 ^5.2 ^5.3 Fission product
↑ Believed to undergo α decay to ¹⁴⁹Pm

Notes

Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
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

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↑ http://www-nds.ipen.br/sgnucdat/b2.pdf^{[dead link]}
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Isotope masses from:
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Isotopic compositions and standard atomic masses from:
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Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
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Isotopes of samarium	Isotopes of europium	Isotopes of gadolinium
Table of nuclides

[3] Bold for isotopes with half-lives longer than the age of the universe (nearly stable)

[5] Abbreviations:
EC: Electron capture
IT: Isomeric transition

[6] Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)

[7] rimordial radionuclide

[FP-8] 5.0 ^5.1 ^5.2 ^5.3 Fission product

[9] Believed to undergo α decay to ¹⁴⁹Pm

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[2] ttp://www-nds.ipen.br/sgnucdat/b2.pdf^{[dead link]}

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[1]

[2]

[n 1]

[3]

[n 2]

[n 3]

[n 4]

[n 5]

[n 6]

v t e Isotopes of the chemical elements
1 H																	2 He
3 Li	4 Be											5 B	6 C	7 N	8 O	9 F	10 Ne
11 Na	12 Mg											13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
19 K	20 Ca	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
37 Rb	38 Sr	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
55 Cs	56 Ba		72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
87 Fr	88 Ra		104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Uut	114 Fl	115 Uup	116 Lv	117 Uus	118 Uuo

		57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu
		89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr
Table of nuclides Categories: Isotopes Tables of nuclides Metastable isotopes Isotopes by element

Isotopes of europium

Contents

Europium-155

Table

Notes

References

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