Naturally occurring europium (₆₃Eu) is composed of two

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...

s, ¹⁵¹Eu and ¹⁵³Eu, with ¹⁵³Eu being the most abundant (52.2% natural abundance). While ¹⁵³Eu is observationally stable, ¹⁵¹Eu was found in 2007 to be unstable and undergo

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...

. The

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

is measured to be (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 10¹⁸ years 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

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 Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...

isotopes, which range from ¹³⁰Eu to ¹⁷⁰Eu, have half-lives that are less than 12.2 seconds. This element also has 18

meta state A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...

s, 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 Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...

, and the primary mode after is

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...

. The primary decay products before ¹⁵³Eu are

isotopes of samarium Naturally occurring samarium (62Sm) is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm (half life: 1.06 y) and 148Sm (7 y), with 152Sm being the most abundant (26. ...

and the primary products after are isotopes of gadolinium.

List of isotopes

, - , ¹³⁰Eu , style="text-align:right" , 63 , style="text-align:right" , 67 , 129.96357(54)# , 1.1(5) ms
.9(+5−3) ms, , , 2+# , , , - , ¹³¹Eu , style="text-align:right" , 63 , style="text-align:right" , 68 , 130.95775(43)# , 17.8(19) ms , , , 3/2+ , , , - , rowspan=2, ¹³²Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 69 , rowspan=2, 131.95437(43)# , rowspan=2, 100# ms , β⁺ , ¹³²Sm , rowspan=2, , rowspan=2, , rowspan=2, , - , p , ¹³¹Sm , - , ¹³³Eu , style="text-align:right" , 63 , style="text-align:right" , 70 , 132.94924(32)# , 200# ms , β⁺ , ¹³³Sm , 11/2−# , , , - , rowspan=2, ¹³⁴Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 71 , rowspan=2, 133.94651(21)# , rowspan=2, 0.5(2) s , β⁺ , ¹³⁴Sm , rowspan=2, , rowspan=2, , rowspan=2, , - , β⁺, p (rare) , ¹³³Pm , - , rowspan=2, ¹³⁵Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 72 , rowspan=2, 134.94182(32)# , rowspan=2, 1.5(2) s , β⁺ , ¹³⁵Sm , rowspan=2, 11/2−# , rowspan=2, , rowspan=2, , - , β⁺, p , ¹³⁴Pm , - , rowspan=2, ¹³⁶Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 73 , rowspan=2, 135.93960(21)# , rowspan=2, 3.3(3) s , β⁺ (99.91%) , ¹³⁶Sm , rowspan=2, (7+) , rowspan=2, , rowspan=2, , - , β⁺, p (.09%) , ¹³⁵Pm , - , rowspan=2 style="text-indent:1em" , ^136mEu , rowspan=2 colspan="3" style="text-indent:2em" , 0(500)# keV , rowspan=2, 3.8(3) s , β⁺ (99.91%) , ¹³⁶Sm , rowspan=2, (3+) , rowspan=2, , rowspan=2, , - , β⁺, p (.09%) , ¹³⁵Pm , - , ¹³⁷Eu , style="text-align:right" , 63 , style="text-align:right" , 74 , 136.93557(21)# , 8.4(5) s , β⁺ , ¹³⁷Sm , 11/2−# , , , - , ¹³⁸Eu , style="text-align:right" , 63 , style="text-align:right" , 75 , 137.93371(3) , 12.1(6) s , β⁺ , ¹³⁸Sm , (6−) , , , - , ¹³⁹Eu , style="text-align:right" , 63 , style="text-align:right" , 76 , 138.929792(14) , 17.9(6) s , β⁺ , ¹³⁹Sm , (11/2)− , , , - , ¹⁴⁰Eu , style="text-align:right" , 63 , style="text-align:right" , 77 , 139.92809(6) , 1.51(2) s , β⁺ , ¹⁴⁰Sm , 1+ , , , - , rowspan=2 style="text-indent:1em" , ^140mEu , rowspan=2 colspan="3" style="text-indent:2em" , 210(15) keV , rowspan=2, 125(2) ms , IT (99%) , ¹⁴⁰Eu , rowspan=2, 5−# , rowspan=2, , rowspan=2, , - , β⁺(1%) , ¹⁴⁰Sm , - , ¹⁴¹Eu , style="text-align:right" , 63 , style="text-align:right" , 78 , 140.924931(14) , 40.7(7) s , β⁺ , ¹⁴¹Sm , 5/2+ , , , - , 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, , rowspan=2, , - , β⁺ (14%) , ¹⁴¹Sm , - , ¹⁴²Eu , style="text-align:right" , 63 , style="text-align:right" , 79 , 141.92343(3) , 2.36(10) s , β⁺ , ¹⁴²Sm , 1+ , , , - , style="text-indent:1em" , ^142mEu , colspan="3" style="text-indent:2em" , 460(30) keV , 1.223(8) min , β⁺ , ¹⁴²Sm , 8− , , , - , ¹⁴³Eu , style="text-align:right" , 63 , style="text-align:right" , 80 , 142.920298(12) , 2.59(2) min , β⁺ , ¹⁴³Sm , 5/2+ , , , - , style="text-indent:1em" , ^143mEu , colspan="3" style="text-indent:2em" , 389.51(4) keV , 50.0(5) µs , , , 11/2− , , , - , ¹⁴⁴Eu , style="text-align:right" , 63 , style="text-align:right" , 81 , 143.918817(12) , 10.2(1) s , β⁺ , ¹⁴⁴Sm , 1+ , , , - , style="text-indent:1em" , ^144mEu , colspan="3" style="text-indent:2em" , 1127.6(6) keV , 1.0(1) µs , , , (8−) , , , - , ¹⁴⁵Eu , style="text-align:right" , 63 , style="text-align:right" , 82 , 144.916265(4) , 5.93(4) d , β⁺ , ¹⁴⁵Sm , 5/2+ , , , - , style="text-indent:1em" , ^145mEu , colspan="3" style="text-indent:2em" , 716.0(3) keV , 490 ns , , , 11/2− , , , - , ¹⁴⁶Eu , style="text-align:right" , 63 , style="text-align:right" , 83 , 145.917206(7) , 4.61(3) d , β⁺ , ¹⁴⁶Sm , 4− , , , - , style="text-indent:1em" , ^146mEu , colspan="3" style="text-indent:2em" , 666.37(16) keV , 235(3) µs , , , 9+ , , , - , rowspan=2, ¹⁴⁷Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 84 , rowspan=2, 146.916746(3) , rowspan=2, 24.1(6) d , β⁺ (99.99%) , ''¹⁴⁷Sm'' , rowspan=2, 5/2+ , rowspan=2, , rowspan=2, , - , α (.0022%) , ¹⁴³Pm , - , rowspan=2, ¹⁴⁸Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 85 , rowspan=2, 147.918086(11) , rowspan=2, 54.5(5) d , β⁺ (100%) , ''¹⁴⁸Sm'' , rowspan=2, 5− , rowspan=2, , rowspan=2, , - , α (9.39×10⁻⁷%) , ¹⁴⁴Pm , - , ¹⁴⁹Eu , style="text-align:right" , 63 , style="text-align:right" , 86 , 148.917931(5) , 93.1(4) d , EC , ¹⁴⁹Sm , 5/2+ , , , - , ¹⁵⁰Eu , style="text-align:right" , 63 , style="text-align:right" , 87 , 149.919702(7) , 36.9(9) y , β⁺ , ¹⁵⁰Sm , 5(−) , , , - , rowspan=3 style="text-indent:1em" , ^150mEu , rowspan=3 colspan="3" style="text-indent:2em" , 42.1(5) keV , rowspan=3, 12.8(1) h , β⁻ (89%) , ¹⁵⁰Gd , rowspan=3, 0− , rowspan=3, , rowspan=3, , - , β⁺ (11%) , ¹⁵⁰Sm , - , IT (5×10⁻⁸%) , ¹⁵⁰Eu , - , ¹⁵¹Eu primordial radionuclide , style="text-align:right" , 63 , style="text-align:right" , 88 , 150.9198502(26) , 4.62×10¹⁸ y , α , ¹⁴⁷Pm , 5/2+ , 0.4781(6) , , - , style="text-indent:1em" , ^151mEu , colspan="3" style="text-indent:2em" , 196.245(10) keV , 58.9(5) µs , , , 11/2− , , , - , rowspan=2, ¹⁵²Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 89 , rowspan=2, 151.9217445(26) , rowspan=2, 13.537(6) y , EC (72.09%), β⁺ (0.027%) , ¹⁵²Sm , rowspan=2, 3− , rowspan=2, , rowspan=2, , - , β⁻ (27.9%) , ''¹⁵²Gd'' , - , 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⁻ (72%) , ''¹⁵²Gd'' , rowspan=2, 0− , rowspan=2, , rowspan=2, , - , β⁺ (28%) , ¹⁵²Sm , - , style="text-indent:1em" , ^152m2Eu , colspan="3" style="text-indent:2em" , 65.2969(4) keV , 0.94(8) µs , , , 1− , , , - , style="text-indent:1em" , ^152m3Eu , colspan="3" style="text-indent:2em" , 78.2331(4) keV , 165(10) ns , , , 1+ , , , - , style="text-indent:1em" , ^152m4Eu , colspan="3" style="text-indent:2em" , 89.8496(4) keV , 384(10) ns , , , 4+ , , , - , style="text-indent:1em" , ^152m5Eu , colspan="3" style="text-indent:2em" , 147.86(10) keV , 96(1) min , , , 8− , , , - , ¹⁵³Eu Fission product , style="text-align:right" , 63 , style="text-align:right" , 90 , 152.9212303(26) , colspan=3 align=center,

Observationally Stable Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. Th ...

Believed to undergo α decay to ¹⁴⁹Pm with a half-life over , 5/2+ , 0.5219(6) , , - , rowspan=2, ¹⁵⁴Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 91 , rowspan=2, 153.9229792(26) , rowspan=2, 8.593(4) y , β⁻ (99.98%) , ¹⁵⁴Gd , rowspan=2, 3− , rowspan=2, , rowspan=2, , - , EC (.02%) , ¹⁵⁴Sm , - , style="text-indent:1em" , ^154m1Eu , colspan="3" style="text-indent:2em" , 145.3(3) keV , 46.3(4) min , IT , ¹⁵⁴Eu , (8−) , , , - , style="text-indent:1em" , ^154m2Eu , colspan="3" style="text-indent:2em" , 68.1702(4) keV , 2.2(1) µs , , , 2+ , , , - , ¹⁵⁵Eu , style="text-align:right" , 63 , style="text-align:right" , 92 , 154.9228933(27) , 4.7611(13) y , β⁻ , ¹⁵⁵Gd , 5/2+ , , , - , ¹⁵⁶Eu , style="text-align:right" , 63 , style="text-align:right" , 93 , 155.924752(6) , 15.19(8) d , β⁻ , ¹⁵⁶Gd , 0+ , , , - , ¹⁵⁷Eu , style="text-align:right" , 63 , style="text-align:right" , 94 , 156.925424(6) , 15.18(3) h , β⁻ , ¹⁵⁷Gd , 5/2+ , , , - , ¹⁵⁸Eu , style="text-align:right" , 63 , style="text-align:right" , 95 , 157.92785(8) , 45.9(2) min , β⁻ , ¹⁵⁸Gd , (1−) , , , - , ¹⁵⁹Eu , style="text-align:right" , 63 , style="text-align:right" , 96 , 158.929089(8) , 18.1(1) min , β⁻ , ¹⁵⁹Gd , 5/2+ , , , - , ¹⁶⁰Eu , style="text-align:right" , 63 , style="text-align:right" , 97 , 159.93197(22)# , 38(4) s , β⁻ , ¹⁶⁰Gd , 1(−) , , , - , ¹⁶¹Eu , style="text-align:right" , 63 , style="text-align:right" , 98 , 160.93368(32)# , 26(3) s , β⁻ , ¹⁶¹Gd , 5/2+# , , , - , ¹⁶²Eu , style="text-align:right" , 63 , style="text-align:right" , 99 , 161.93704(32)# , 10.6(10) s , β⁻ , ¹⁶²Gd , , , , - , ¹⁶³Eu , style="text-align:right" , 63 , style="text-align:right" , 100 , 162.93921(54)# , 7.7(4) s , β⁻ , ¹⁶³Gd , 5/2+# , , , - , style="text-indent:1em" , ^163mEu , colspan="3" style="text-indent:2em" , 964.5(10) keV , 911(24) ns , , , (13/2−) , , , - , ¹⁶⁴Eu , style="text-align:right" , 63 , style="text-align:right" , 101 , 163.94299(64)# , 4.16(19) s , β⁻ , ¹⁶⁴Gd , , , , - , ¹⁶⁵Eu , style="text-align:right" , 63 , style="text-align:right" , 102 , 164.94572(75)# , , β⁻ , ¹⁶⁵Gd , 5/2+# , , , - , rowspan=2, ¹⁶⁶Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 103 , rowspan=2, 165.94997(86)# , rowspan=2, , β⁻ (99.37%) , ¹⁶⁶Gd , rowspan=2, , rowspan=2, , rowspan=2, , - , β⁻, n (0.63%) , ¹⁶⁵Gd , - , rowspan=2, ¹⁶⁷Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 104 , rowspan=2, 166.95321(86)# , rowspan=2, , β⁻ (98.05%) , ¹⁶⁷Gd , rowspan=2, 5/2+# , rowspan=2, , rowspan=2, , - , β⁻, n (1.95%) , ¹⁶⁶Gd , - , rowspan=2, ¹⁶⁸Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 105 , rowspan=2, , rowspan=2, , β⁻ (96.05%) , ¹⁶⁸Gd , rowspan=2, , rowspan=2, , rowspan=2, , - , β⁻, n (3.95%) , ¹⁶⁷Gd , - , rowspan=2, ¹⁶⁹Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 106 , rowspan=2, , rowspan=2, , β⁻ (85.38%) , ¹⁶⁹Gd , rowspan=2, , rowspan=2, , rowspan=2, , - , β⁻, n (14.62%) , ¹⁶⁸Gd , - , rowspan=2, ¹⁷⁰Eu , rowspan=2 style="text-align:right" , 63 , rowspan=2 style="text-align:right" , 107 , rowspan=2, , rowspan=2, , β⁻ , ¹⁷⁰Gd , rowspan=2, , rowspan=2, , rowspan=2, , - , β⁻, n , ¹⁶⁹Gd

Europium-155

Europium-155 is a fission product with a

of 4.76 years. It has a maximum

decay energy The decay energy is the energy change of a nucleus having undergone a radioactive decay. Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy ...

of 252

keV Kev can refer to: Given name * Kev Adams, French comedian, actor, screenwriter and film producer born Kevin Smadja in 1991 * Kevin Kev Carmody (born 1946), Indigenous Australian singer-songwriter * Kev Coghlan (born 1988), Scottish Grand Prix moto ...

. In a

thermal reactor A thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and struct ...

(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 Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons, ...

cross section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...

(about 3900 barns for

thermal neutrons The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium with ...

, 16000 resonance integral) means that most of even the small amount produced is destroyed in the course of the nuclear fuel's

burnup In nuclear power technology, burnup (also known as fuel utilization) is a measure of how much energy is extracted from a primary nuclear fuel source. It is measured as the fraction of fuel atoms that underwent fission in %FIMA (fissions per ini ...

. 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 Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons ...

. 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.

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Europium Europium