:Isotopes of europium

Naturally occurring europium (₆₃Eu) is composed of two isotopes, ¹⁵¹Eu and ¹⁵³Eu, with ¹⁵³Eu being the most abundant (52.2% natural abundance). While ¹⁵³Eu is observationally stable (theoretically can undergo alpha decay with half-life over 5.5×10¹⁷ years), ¹⁵¹Eu was found in 2007 to be unstable and undergo alpha decay.{{cite journal|title=Search for α decay of natural europium|last1=Belli |first1=P.|doi=10.1016/j.nuclphysa.2007.03.001|date=2007|journal=Nuclear Physics A|volume=789|issue= 1–4|pages=15–29|display-authors=1|last2=Bernabei|first2=R|last3=Cappella|first3=F|last4=Cerulli|first4=R|last5=Dai|first5=C|last6=Danevich|first6=F|last7=Dangelo|first7=A|last8=Incicchitti|first8=A|last9=Kobychev|first9=V|last10= Nagorny|first10= S.S.|last11= Nisi|first11= S.|last12= Nozzoli|first12= F.|last13= Prosperi|first13= D.|last14= Tretyak|first14= V.I.|last15= Yurchenko|first15= S.S.|bibcode = 2007NuPhA.789...15B }} The half-life is measured to be (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 10¹⁸ years

{{cite journal

|title=Discovery of the ¹⁵¹Eu α decay

|journal=Journal of Physics G: Nuclear and Particle Physics

|volume=41 |number=7 |pages=075101

|doi=10.1088/0954-3899/41/7/075101 |display-authors=etal|arxiv=1311.2834|bibcode=2014JPhG...41g5101C|s2cid=116920467 }} which corresponds to 1 alpha decay per two minutes in every kilogram of natural europium. Besides the 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, ¹⁵⁴Eu with a half-life of 8.593 years, and ¹⁵⁵Eu with a half-life of 4.7612 years. The majority of the remaining radioactive isotopes, which range from ¹³⁰Eu to ¹⁷⁰Eu, have half-lives that are less than 12.2 seconds. This element also has 18 metastable isomers, with the most stable being ^150mEu (t_1/2 12.8 hours), ^152m1Eu (t_1/2 9.3116 hours) and ^152m5Eu (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.

List of isotopes

{{Isotopes table

|symbol=Eu

|refs=NUBASE2020, AME2020 II

|notes=m, unc(), mass#, exen#, hl#, hl-nst, spin(), spin#, daughter-st, daughter-nst, p, A, B+, B-, IT, EC

}}

|-id=Europium-130

| ¹³⁰Eu

| style="text-align:right" | 63

| style="text-align:right" | 67

| 129.96402(58)#

| 1.0(4) ms

| p

| ¹²⁹Sm

| (1+)

|-id=Europium-131

| rowspan=3|¹³¹Eu

| rowspan=3 style="text-align:right" | 63

| rowspan=3 style="text-align:right" | 68

| rowspan=3|130.95763(43)#

| rowspan=3|17.8(19) ms

| p (89%)

| ¹³⁰Sm

| rowspan=3|3/2+

| rowspan=3|

| β⁺ (?%)

| ¹³¹Sm

| β⁺, p (?%)

| ¹³⁰Pm

|-id=Europium-134

| rowspan=2|¹³⁴Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 71

| rowspan=2|133.94654(32)#

| rowspan=2|0.5(2) s

| β⁺

| ¹³⁴Sm

| rowspan=2|

| β⁺, p (?%)

| ¹³³Pm

|-id=Europium-135

| ¹³⁵Eu

| style="text-align:right" | 63

| style="text-align:right" | 72

| 134.94187(21)#

| 1.5(2) s

| β⁺

| ¹³⁵Sm

| 5/2+#

|-id=Europium-136

| rowspan=2|¹³⁶Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 73

| rowspan=2|135.93962(21)#

| rowspan=2|3.3(3) s

| β⁺ (99.91%)

| ¹³⁶Sm

| rowspan=2|6+#

| rowspan=2|

| β⁺, p (0.09%)

| ¹³⁵Pm

|-id=Europium-136m

| rowspan=2 style="text-indent:1em" | ^136mEuOrder of ground state and isomer is uncertain.

| rowspan=2 colspan="3" style="text-indent:2em" | 100(100)# keV

| rowspan=2|3.8(3) s

| β⁺ (99.91%)

| ¹³⁶Sm

| rowspan=2|1+#

| rowspan=2|

| β⁺, p (0.09%)

| ¹³⁵Pm

|-id=Europium-137

| ¹³⁷Eu

| style="text-align:right" | 63

| style="text-align:right" | 74

| 136.9354307(47)

| 8.4(5) s

| β⁺

| ¹³⁷Sm

| 5/2+#

|-id=Europium-138

| ¹³⁸Eu

| style="text-align:right" | 63

| style="text-align:right" | 75

| 137.933709(30)

| 5# s

| 2−#

|-id=Europium-138m

| style="text-indent:1em" | ^138mEu

| colspan="3" style="text-indent:2em" | 100(50)# keV

| 12.1(6) s

| β⁺

| ¹³⁸Sm

| 7−#

|-id=Europium-139

| ¹³⁹Eu

| style="text-align:right" | 63

| style="text-align:right" | 76

| 138.929792(14)

| 17.9(6) s

| β⁺

| ¹³⁹Sm

| (11/2)−

|-id=Europium-139m

| style="text-indent:1em" | ^139mEu

| colspan="3" style="text-indent:2em" | 148.3(3) keV

| 10(2) μs

| IT

| ¹³⁹Eu

| (7/2+)

|-id=Europium-140

| rowspan=2|¹⁴⁰Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 77

| rowspan=2|139.928088(55)

| rowspan=2|1.51(2) s

| β⁺ (95.1%)

| rowspan=2|¹⁴⁰Sm

| rowspan=2|1+

| rowspan=2|

| EC (4.9%)

|-id=Europium-140m1

| rowspan=2 style="text-indent:1em" | ^140m1Eu

| rowspan=2 colspan="3" style="text-indent:2em" | 210(14) keV

| rowspan=2|125(2) ms

| IT (>99%)

| ¹⁴⁰Eu

| rowspan=2|(5−)

| rowspan=2|

| β⁺ (>1%)

| ¹⁴⁰Sm

|-id=Europium-140m2

| style="text-indent:1em" | ^140m2Eu

| colspan="3" style="text-indent:2em" | 669(14) keV

| 299.8(21) ns

| IT

| ¹⁴⁰Eu

| (8+)

|-id=Europium-141

| ¹⁴¹Eu

| style="text-align:right" | 63

| style="text-align:right" | 78

| 140.924932(14)

| 40.7(7) s

| β⁺

| ¹⁴¹Sm

| 5/2+

|-id=Europium-141m

| rowspan=2 style="text-indent:1em" | ^141mEu

| rowspan=2 colspan="3" style="text-indent:2em" | 96.45(7) keV

| rowspan=2|2.7(3) s

| IT (86%)

| ¹⁴¹Eu

| rowspan=2|11/2−

| rowspan=2|

| β⁺ (14%)

| ¹⁴¹Sm

|-id=Europium-142

| rowspan=2|¹⁴²Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 79

| rowspan=2|141.923447(32)

| rowspan=2|2.36(10) s

| β⁺ (89.9%)

| ¹⁴²Sm

| rowspan=2|1+

| rowspan=2|

| EC (11.1%)

| ¹⁴²Sm

|-id=Europium-142m

| style="text-indent:1em" | ^142mEu

| colspan="3" style="text-indent:2em" | 450(30) keV

| 1.223(8) min

| β⁺

| ¹⁴²Sm

| 8−

|-id=Europium-143

| ¹⁴³Eu

| style="text-align:right" | 63

| style="text-align:right" | 80

| 142.920299(12)

| 2.59(2) min

| β⁺

| ¹⁴³Sm

| 5/2+

|-id=Europium-143m

| style="text-indent:1em" | ^143mEu

| colspan="3" style="text-indent:2em" | 389.51(4) keV

| 50.0(5) μs

| IT

| ¹⁴³Eu

| 11/2−

|-id=Europium-144

| ¹⁴⁴Eu

| style="text-align:right" | 63

| style="text-align:right" | 81

| 143.918819(12)

| 10.2(1) s

| β⁺

| ¹⁴⁴Sm

| 1+

|-id=Europium-144m

| style="text-indent:1em" | ^144mEu

| colspan="3" style="text-indent:2em" | 1127.6(6) keV

| 1.0(1) μs

| IT

|¹⁴⁴Eu

| 8−

|-id=Europium-145

| ¹⁴⁵Eu

| style="text-align:right" | 63

| style="text-align:right" | 82

| 144.9162727(33)

| 5.93(4) d

| β⁺

| ¹⁴⁵Sm

| 5/2+

|-id=Europium-145m

| style="text-indent:1em" | ^145mEu

| colspan="3" style="text-indent:2em" | 716.0(3) keV

| 490(30) ns

| IT

| ¹⁴⁵Eu

| 11/2−

|-id=Europium-146

| ¹⁴⁶Eu

| style="text-align:right" | 63

| style="text-align:right" | 83

| 145.9172109(65)

| 4.61(3) d

| β⁺

| ¹⁴⁶Sm

| 4−

|-id=Europium-146m

| style="text-indent:1em" | ^146mEu

| colspan="3" style="text-indent:2em" | 666.33(11) keV

| 235(3) μs

| IT

| ¹⁴⁶Eu

| 9+

|-id=Europium-147

| rowspan=2|¹⁴⁷Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 84

| rowspan=2|146.9167524(28)

| rowspan=2|24.1(6) d

| β⁺

| ¹⁴⁷Sm

| rowspan=2|5/2+

| rowspan=2|

| α (0.0022%)

| ¹⁴³Pm

|-id=Europium-147m

| style="text-indent:1em" | ^147mEu

| colspan="3" style="text-indent:2em" | 625.27(5) keV

| 765(15) ns

| IT

| ¹⁴⁷Eu

| 11/2−

|-id=Europium-148

| rowspan=2|¹⁴⁸Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 85

| rowspan=2|147.918091(11)

| rowspan=2|54.5(5) d

| β⁺

| ¹⁴⁸Sm

| rowspan=2|5−

| rowspan=2|

| α (9.4×10⁻⁷%)

| ¹⁴⁴Pm

|-id=Europium-148m

| style="text-indent:1em" | ^148mEu

| colspan="3" style="text-indent:2em" | 720.4(3) keV

| 162(8) ns

| IT

| ¹⁴⁸Eu

| 9+

|-id=Europium-149

| ¹⁴⁹Eu

| style="text-align:right" | 63

| style="text-align:right" | 86

| 148.9179369(42)

| 93.1(4) d

| EC

| ¹⁴⁹Sm

| 5/2+

|-id=Europium-149m

| style="text-indent:1em" | ^149mEu

| colspan="3" style="text-indent:2em" | 496.386(2) keV

| 2.45(5) μs

| IT

| ¹⁴⁹Eu

| 11/2−

|-id=Europium-150

| ¹⁵⁰Eu

| style="text-align:right" | 63

| style="text-align:right" | 87

| 149.9197071(67)

| 36.9(9) y

| β⁺

| ¹⁵⁰Sm

| 5−

|-id=Europium-150m

| rowspan=3 style="text-indent:1em" | ^150mEu

| rowspan=3 colspan="3" style="text-indent:2em" | 41.7(10) keV

| rowspan=3|12.8(1) h

| β⁻ (89%)

| ¹⁵⁰Gd

| rowspan=3|0−

| rowspan=3|

| β⁺ (11%)

| ¹⁵⁰Sm

| IT (<5×10⁻⁸%){{cite web|url=https://www.nndc.bnl.gov/ensnds/150/Eu/adopted.pdf|title=Adopted Levels for ¹⁵⁰Eu|publisher=NNDC Chart of Nuclides}}

| ¹⁵⁰Eu

|-id=Europium-151

| ¹⁵¹Euprimordial radionuclide

| style="text-align:right" | 63

| style="text-align:right" | 88

| 150.9198566(13)

| 4.6(12)×10¹⁸ y

| α

| ¹⁴⁷Pm

| 5/2+

| 0.4781(6)

|-id=Europium-151m

| style="text-indent:1em" | ^151mEu

| colspan="3" style="text-indent:2em" | 196.245(10) keV

| 58.9(5) μs

| IT

| ¹⁵¹Eu

| 11/2−

|-id=Europium-152

| rowspan=2|¹⁵²Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 89

| rowspan=2|151.9217510(13)

| rowspan=2|13.517(6) y

| β⁺ (72.08%)

| ¹⁵²Sm

| rowspan=2|3−

| rowspan=2|

| β⁻ (27.92%)

| ¹⁵²Gd

|-id=Europium-152m1

| rowspan=2 style="text-indent:1em" | ^152m1Eu

| rowspan=2 colspan="3" style="text-indent:2em" | 45.5998(4) keV

| rowspan=2|9.3116(13) h

| β⁻ (73%)

| ¹⁵²Gd

| rowspan=2|0−

| rowspan=2|

| β⁺ (27%)

| ¹⁵²Sm

|-id=Europium-152m2

| style="text-indent:1em" | ^152m2Eu

| colspan="3" style="text-indent:2em" | 65.2969(4) keV

| 940(80) ns

| IT

| ¹⁵²Eu

| 1−

|-id=Europium-152m3

| style="text-indent:1em" | ^152m3Eu

| colspan="3" style="text-indent:2em" | 78.2331(4) keV

| 165(10) ns

| IT

| ¹⁵²Eu

| 1+

|-id=Europium-152m4

| style="text-indent:1em" | ^152m4Eu

| colspan="3" style="text-indent:2em" | 89.8496(4) keV

| 384(10) ns

| IT

| ¹⁵²Eu

| 4+

|-id=Europium-152m5

| style="text-indent:1em" | ^152m5Eu

| colspan="3" style="text-indent:2em" | 147.86(10) keV

| 95.8(4) min

| IT

| ¹⁵²Eu

| 8−

|-id=Europium-153

| ¹⁵³EuFission product

| style="text-align:right" | 63

| style="text-align:right" | 90

| 152.9212368(13)

| colspan=3 align=center|Observationally StableBelieved to undergo α decay to ¹⁴⁹Pm with a half-life over {{val|5.5|e=17|u=years}}{{cite journal |last1=Danevich |first1=F. A. |last2=Andreotti |first2=E. |last3=Hult |first3=M. |last4=Marissens |first4=G. |last5=Tretyak |first5=V. I. |last6=Yuksel |first6=A. |title=Search for α decay of ¹⁵¹Eu to the first excited level of ¹⁴⁷Pm using underground γ-ray spectrometry |journal = European Physical Journal A |volume=48 |number=157 |date=2012 |page=157 |doi=10.1140/epja/i2012-12157-7|arxiv=1301.3465 |bibcode=2012EPJA...48..157D |s2cid=118657922 }}{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |display-authors=3 |title=Experimental searches for rare alpha and beta decays |journal=European Physical Journal A |date=2019 |volume=55 |issue=8 |pages=140–1–140–7 |doi=10.1140/epja/i2019-12823-2 |issn=1434-601X |arxiv=1908.11458|bibcode=2019EPJA...55..140B |s2cid=201664098 }}

| 5/2+

| 0.5219(6)

|-id=Europium-153m

| style="text-indent:1em" | ^153mEu

| colspan="3" style="text-indent:2em" | 1771.0(4) keV

| 475(10) ns

| IT

| ¹⁵³Eu

| 19/2−

|-id=Europium-154

| rowspan=2|¹⁵⁴Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 91

| rowspan=2|153.9229857(13)

| rowspan=2|8.592(3) y

| β⁻ (99.98%)

| ¹⁵⁴Gd

| rowspan=2|3−

| rowspan=2|

| EC (0.018%)

| ¹⁵⁴Sm

|-id=Europium-154m1

| style="text-indent:1em" | ^154m1Eu

| colspan="3" style="text-indent:2em" | 68.1702(4) keV

| 2.2(1) μs

| IT

| ¹⁵⁴Eu

| 2+

|-id=Europium-154m2

| style="text-indent:1em" | ^154m2Eu

| colspan="3" style="text-indent:2em" | 145.3(3) keV

| 46.3(4) min

| IT

| ¹⁵⁴Eu

| (8−)

| ¹⁵⁵Eu

| style="text-align:right" | 63

| style="text-align:right" | 92

| 154.9228998(13)

| 4.742(8) y

| β⁻

| ¹⁵⁵Gd

| 5/2+

|-id=Europium-156

| ¹⁵⁶Eu

| style="text-align:right" | 63

| style="text-align:right" | 93

| 155.9247630(38)

| 15.19(8) d

| β⁻

| ¹⁵⁶Gd

| 0+

|-id=Europium-157

| ¹⁵⁷Eu

| style="text-align:right" | 63

| style="text-align:right" | 94

| 156.9254326(45)

| 15.18(3) h

| β⁻

| ¹⁵⁷Gd

| 5/2+

|-id=Europium-158

| ¹⁵⁸Eu

| style="text-align:right" | 63

| style="text-align:right" | 95

| 157.9277822(22)

| 45.9(2) min

| β⁻

| ¹⁵⁸Gd

| 1−

|-id=Europium-159

| ¹⁵⁹Eu

| style="text-align:right" | 63

| style="text-align:right" | 96

| 158.9290995(46)

| 18.1(1) min

| β⁻

| ¹⁵⁹Gd

| 5/2+

|-id=Europium-160

| ¹⁶⁰Eu

| style="text-align:right" | 63

| style="text-align:right" | 97

| 159.93183698(97)

| 42.6(5) s

| β⁻

| ¹⁶⁰Gd

| (5−)

|-id=Europium-160m

| style="text-indent:1em" | ^160mEu

| colspan="3" style="text-indent:2em" | 93.0(12) keV

| 30.8(5) s

| IT

| ¹⁶⁰Eu

| (1−)

|-id=Europium-161

| ¹⁶¹Eu

| style="text-align:right" | 63

| style="text-align:right" | 98

| 160.933664(11)

| 26.2(23) s

| β⁻

| ¹⁶¹Gd

| 5/2+#

|-id=Europium-162

| ¹⁶²Eu

| style="text-align:right" | 63

| style="text-align:right" | 99

| 161.9369583(14)

| ~10 s

| β⁻

| ¹⁶²Gd

| 1+#

|-id=Europium-162m

| style="text-indent:1em" | ^162mEu

| colspan="3" style="text-indent:2em" | 158.0(17) keV

| 15.0(5) s

| IT

| ¹⁶²Eu

| (6+)

|-id=Europium-163

| ¹⁶³Eu

| style="text-align:right" | 63

| style="text-align:right" | 100

| 162.93926551(97)

| 7.7(4) s

| β⁻

| ¹⁶³Gd

| 5/2+#

|-id=Europium-163m

| style="text-indent:1em" | ^163mEu

| colspan="3" style="text-indent:2em" | 964.5(5) keV

| 911(24) ns

| IT

| ¹⁶³Eu

| (13/2−)

|-id=Europium-164

| ¹⁶⁴Eu

| style="text-align:right" | 63

| style="text-align:right" | 101

| 163.9428529(22)

| 4.16(19) s

| β⁻

| ¹⁶⁴Gd

| 3−#

|-id=Europium-165

| ¹⁶⁵Eu

| style="text-align:right" | 63

| style="text-align:right" | 102

| 164.9455401(56)

| {{val|2.163|0.139|0.120|u=s}}{{cite journal |last1=Kiss |first1=G. G. |last2=Vitéz-Sveiczer |first2=A. |last3=Saito |first3=Y. |display-authors=et al. |title=Measuring the β-decay properties of neutron-rich exotic Pm, Sm, Eu, and Gd isotopes to constrain the nucleosynthesis yields in the rare-earth region |journal=The Astrophysical Journal |volume=936 |issue=107 |date=2022 |page=107 |doi=10.3847/1538-4357/ac80fc|bibcode=2022ApJ...936..107K |doi-access=free |hdl=2117/375253 |hdl-access=free }}

| β⁻

| ¹⁶⁵Gd

| 5/2+#

|-id=Europium-166

| rowspan=2|¹⁶⁶Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 103

| rowspan=2|165.94981(11)#

| rowspan=2|{{val|1.277|0.100|0.145|u=s}}

| β⁻ (99.37%)

| ¹⁶⁶Gd

| rowspan=2|0−#

| rowspan=2|

| β⁻, n (0.63%)

| ¹⁶⁵Gd

|-id=Europium-167

| rowspan=2|¹⁶⁷Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 104

| rowspan=2|166.95301(43)#

| rowspan=2|{{val|852|76|54|u=ms}}

| β⁻ (98.05%)

| ¹⁶⁷Gd

| rowspan=2|5/2+#

| rowspan=2|

| β⁻, n (1.95%)

| ¹⁶⁶Gd

|-id=Europium-168

| rowspan=2|¹⁶⁸Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 105

| rowspan=2|167.95786(43)#

| rowspan=2|{{val|440|48|47|u=ms}}

| β⁻ (96.05%)

| ¹⁶⁸Gd

| rowspan=2|6−#

| rowspan=2|

| β⁻, n (3.95%)

| ¹⁶⁷Gd

|-id=Europium-169

| rowspan=2|¹⁶⁹Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 106

| rowspan=2|168.96172(54)#

| rowspan=2|{{val|389|92|88|u=ms}}

| β⁻ (85.38%)

| ¹⁶⁹Gd

| rowspan=2|5/2+#

| rowspan=2|

| β⁻, n (14.62%)

| ¹⁶⁸Gd

|-id=Europium-170

| rowspan=2|¹⁷⁰Eu

| rowspan=2 style="text-align:right" | 63

| rowspan=2 style="text-align:right" | 107

| rowspan=2|169.96687(54)#

| rowspan=2|{{val|197|74|71|u=ms}}

| β⁻ (>76%)

| ¹⁷⁰Gd

| rowspan=2|

| β⁻, n (<24%)

| ¹⁶⁹Gd

Europium-155

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 half-life are all far less than that of 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.{{Cite web |url=http://www-nds.ipen.br/sgnucdat/b2.pdf |title=Archived copy |access-date=2011-04-02 |archive-url=https://web.archive.org/web/20110706160615/http://www-nds.ipen.br/sgnucdat/b2.pdf |archive-date=2011-07-06 |url-status=dead }}

class=wikitable !Isotope!!Half-life!!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

References

Isotope masses from:
{{NUBASE 2003}}
Isotopic compositions and standard atomic masses from:
{{CIAAW2003}}
{{CIAAW 2005}}
Half-life, spin, and isomer data selected from the following sources.
{{NUBASE 2003}}
{{NNDC}}
{{CRC85|chapter=11}}

Category:Europium

Europium