Isotopes of europium

Naturally occurring europium (₆₃Eu) is composed of two isotopes, ¹⁵¹Eu and ¹⁵³Eu, with ¹⁵³Eu being the more abundant (52.2% natural abundance). While ¹⁵³Eu is observationally stable, ¹⁵¹Eu was found in 2007 to be unstable and undergo alpha decay; its measured half-life of 4.6 ÃƒÂ— 10¹⁸ years corresponds to 1 alpha decay per two minutes per kilogram of natural europium, so for practical purposes it can be considered stable. Besides the natural radioisotope ¹⁵¹Eu, artificial radioisotopes from ¹³⁰Eu to ¹⁷⁰Eu have been made, with the most stable being ¹⁵⁰Eu with a half-life of 36.9 years, ¹⁵²Eu with a half-life of 13.517 years, ¹⁵⁴Eu with a half-life of 8.592 years, and ¹⁵⁵Eu with a half-life of 4.742 years. All the others have half-lives shorter than 100 days, with the majority shorter than 3 minutes.

This element also has 27 metastable isomers, with the most stable being ^150mEu (12.8 hours), ^152m1Eu (9.3116 hours) and ^152m5Eu (96 minutes). The primary decay mode for isotopes lighter than ¹⁵³Eu is electron capture to samarium isotopes, and the primary mode for heavier isotopes is beta minus decay to gadolinium isotopes. ¹⁵²Eu and ¹⁵⁴Eu can decay either way, as can ^150mEu (meta state only).

List of isotopes

|-id=Europium-130 | ¹³⁰Eu | style="text-align:right" | 63 | style="text-align:right" | 67 | 129.96402(58)# | 1.0(4)&nbsp;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)&nbsp;ms | p (89%) | ¹³⁰Sm | rowspan=3|3/2+ | rowspan=3| | rowspan=3| |- | β⁺ (?%) | ¹³¹Sm |- | β⁺, p (?%) | ¹³⁰Pm |-id=Europium-132 | ¹³²Eu | style="text-align:right" | 63 | style="text-align:right" | 69 | 131.95470(43)# | 100#&nbsp;ms<br>[>310&nbsp;ns] | | | 1+# | | |-id=Europium-133 | ¹³³Eu | style="text-align:right" | 63 | style="text-align:right" | 70 | 132.94929(32)# | 200#&nbsp;ms<br>[>310&nbsp;ns] | | | 5/2+# | | |-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)&nbsp;s | β⁺ | ¹³⁴Sm | rowspan=2| | rowspan=2| | 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)&nbsp;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)&nbsp;s | β⁺ (99.91%) | ¹³⁶Sm | rowspan=2|6+# | rowspan=2| | rowspan=2| |- | β⁺, p (0.09%) | ¹³⁵Pm |-id=Europium-136m | rowspan=2 style="text-indent:1em" | ^136mEu | rowspan=2 colspan="3" style="text-indent:2em" | 100(100)#&nbsp;keV | rowspan=2|3.8(3)&nbsp;s | β⁺ (99.91%) | ¹³⁶Sm | rowspan=2|1+# | rowspan=2| | 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)&nbsp;s | β⁺ | ¹³⁷Sm | 5/2+# | | |-id=Europium-138 | ¹³⁸Eu | style="text-align:right" | 63 | style="text-align:right" | 75 | 137.933709(30) | 5#&nbsp;s | | | 2−# | | |-id=Europium-138m | style="text-indent:1em" | ^138mEu | colspan="3" style="text-indent:2em" | 100(50)#&nbsp;keV | 12.1(6)&nbsp;s | β⁺ | ¹³⁸Sm | 7−# | | |-id=Europium-139 | ¹³⁹Eu | style="text-align:right" | 63 | style="text-align:right" | 76 | 138.929792(14) | 17.9(6)&nbsp;s | β⁺ | ¹³⁹Sm | (11/2)− | | |-id=Europium-139m | style="text-indent:1em" | ^139mEu | colspan="3" style="text-indent:2em" | 148.3(3)&nbsp;keV | 10(2)&nbsp;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)&nbsp;s | β⁺ (95.1%) | rowspan=2|¹⁴⁰Sm | rowspan=2|1+ | rowspan=2| | 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)&nbsp;keV | rowspan=2|125(2)&nbsp;ms | IT (>99%) | ¹⁴⁰Eu | rowspan=2|(5−) | rowspan=2| | rowspan=2| |- | β⁺ (>1%) | ¹⁴⁰Sm |-id=Europium-140m2 | style="text-indent:1em" | ^140m2Eu | colspan="3" style="text-indent:2em" | 669(14)&nbsp;keV | 299.8(21)&nbsp;ns | IT | ¹⁴⁰Eu | (8+) | | |-id=Europium-141 | ¹⁴¹Eu | style="text-align:right" | 63 | style="text-align:right" | 78 | 140.924932(14) | 40.7(7)&nbsp;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)&nbsp;keV | rowspan=2|2.7(3)&nbsp;s | IT (86%) | ¹⁴¹Eu | rowspan=2|11/2− | rowspan=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)&nbsp;s | β⁺ (89.9%) | ¹⁴²Sm | rowspan=2|1+ | rowspan=2| | rowspan=2| |- | EC (11.1%) | ¹⁴²Sm |-id=Europium-142m | style="text-indent:1em" | ^142mEu | colspan="3" style="text-indent:2em" | 450(30)&nbsp;keV | 1.223(8)&nbsp;min | β⁺ | ¹⁴²Sm | 8− | | |-id=Europium-143 | ¹⁴³Eu | style="text-align:right" | 63 | style="text-align:right" | 80 | 142.920299(12) | 2.59(2)&nbsp;min | β⁺ | ¹⁴³Sm | 5/2+ | | |-id=Europium-143m | style="text-indent:1em" | ^143mEu | colspan="3" style="text-indent:2em" | 389.51(4)&nbsp;keV | 50.0(5)&nbsp;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)&nbsp;s | β⁺ | ¹⁴⁴Sm | 1+ | | |-id=Europium-144m | style="text-indent:1em" | ^144mEu | colspan="3" style="text-indent:2em" | 1127.6(6)&nbsp;keV | 1.0(1)&nbsp;μs | IT |¹⁴⁴Eu | 8− | | |-id=Europium-145 | ¹⁴⁵Eu | style="text-align:right" | 63 | style="text-align:right" | 82 | 144.9162727(33) | 5.93(4)&nbsp;d | β⁺ | ¹⁴⁵Sm | 5/2+ | | |-id=Europium-145m | style="text-indent:1em" | ^145mEu | colspan="3" style="text-indent:2em" | 716.0(3)&nbsp;keV | 490(30)&nbsp;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)&nbsp;d | β⁺ | ¹⁴⁶Sm | 4− | | |-id=Europium-146m | style="text-indent:1em" | ^146mEu | colspan="3" style="text-indent:2em" | 666.33(11)&nbsp;keV | 235(3)&nbsp;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)&nbsp;d | β⁺ | ¹⁴⁷Sm | rowspan=2|5/2+ | rowspan=2| | rowspan=2| |- | α (0.0022%) | ¹⁴³Pm |-id=Europium-147m | style="text-indent:1em" | ^147mEu | colspan="3" style="text-indent:2em" | 625.27(5)&nbsp;keV | 765(15)&nbsp;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)&nbsp;d | β⁺ | ¹⁴⁸Sm | rowspan=2|5− | rowspan=2| | 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)&nbsp;keV | 162(8)&nbsp;ns | IT | ¹⁴⁸Eu | 9+ | | |-id=Europium-149 | ¹⁴⁹Eu | style="text-align:right" | 63 | style="text-align:right" | 86 | 148.9179369(42) | 93.1(4)&nbsp;d | EC | ¹⁴⁹Sm | 5/2+ | | |-id=Europium-149m | style="text-indent:1em" | ^149mEu | colspan="3" style="text-indent:2em" | 496.386(2)&nbsp;keV | 2.45(5)&nbsp;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)&nbsp;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)&nbsp;keV | rowspan=3|12.8(1)&nbsp;h | β^− (89%) | ¹⁵⁰Gd | rowspan=3|0− | rowspan=3| | rowspan=3| |- | β⁺ (11%) | ¹⁵⁰Sm |- | IT (<5×10^{−8}%) | ¹⁵⁰Eu |-id=Europium-151 | ¹⁵¹Eu | style="text-align:right" | 63 | style="text-align:right" | 88 | 150.9198566(13) | 4.6(12)×10¹⁸&nbsp;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)&nbsp;keV | 58.9(5)&nbsp;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)&nbsp;y | β⁺ (72.08%) | ¹⁵²Sm | rowspan=2|3− | rowspan=2| | 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)&nbsp;keV | rowspan=2|9.3116(13)&nbsp;h | β^− (73%) | ¹⁵²Gd | rowspan=2|0− | rowspan=2| | rowspan=2| |- | β⁺ (27%) | ¹⁵²Sm |-id=Europium-152m2 | style="text-indent:1em" | ^152m2Eu | colspan="3" style="text-indent:2em" | 65.2969(4)&nbsp;keV | 940(80)&nbsp;ns | IT | ¹⁵²Eu | 1− | | |-id=Europium-152m3 | style="text-indent:1em" | ^152m3Eu | colspan="3" style="text-indent:2em" | 78.2331(4)&nbsp;keV | 165(10)&nbsp;ns | IT | ¹⁵²Eu | 1+ | | |-id=Europium-152m4 | style="text-indent:1em" | ^152m4Eu | colspan="3" style="text-indent:2em" | 89.8496(4)&nbsp;keV | 384(10)&nbsp;ns | IT | ¹⁵²Eu | 4+ | | |-id=Europium-152m5 | style="text-indent:1em" | ^152m5Eu | colspan="3" style="text-indent:2em" | 147.86(10)&nbsp;keV | 95.8(4)&nbsp;min | IT | ¹⁵²Eu | 8− | | |-id=Europium-153 | ¹⁵³Eu | style="text-align:right" | 63 | style="text-align:right" | 90 | 152.9212368(13) | colspan=3 align=center|Observationally Stable | 5/2+ | 0.5219(6) | |-id=Europium-153m | style="text-indent:1em" | ^153mEu | colspan="3" style="text-indent:2em" | 1771.0(4)&nbsp;keV | 475(10)&nbsp;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)&nbsp;y | β^− (99.98%) | ¹⁵⁴Gd | rowspan=2|3− | rowspan=2| | rowspan=2| |- | EC (0.02%) | ¹⁵⁴Sm |-id=Europium-154m1 | style="text-indent:1em" | ^154m1Eu | colspan="3" style="text-indent:2em" | 68.1702(4)&nbsp;keV | 2.2(1)&nbsp;μs | IT | ¹⁵⁴Eu | 2+ | | |-id=Europium-154m2 | style="text-indent:1em" | ^154m2Eu | colspan="3" style="text-indent:2em" | 145.3(3)&nbsp;keV | 46.3(4)&nbsp;min | IT | ¹⁵⁴Eu | (8−) | | |- | ¹⁵⁵Eu | style="text-align:right" | 63 | style="text-align:right" | 92 | 154.9228998(13) | 4.742(8)&nbsp;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)&nbsp;d | β^− | ¹⁵⁶Gd | 0+ | | |-id=Europium-157 | ¹⁵⁷Eu | style="text-align:right" | 63 | style="text-align:right" | 94 | 156.9254326(45) | 15.18(3)&nbsp;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)&nbsp;min | β^− | ¹⁵⁸Gd | 1− | | |-id=Europium-159 | ¹⁵⁹Eu | style="text-align:right" | 63 | style="text-align:right" | 96 | 158.9290995(46) | 18.1(1)&nbsp;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)&nbsp;s | β^− | ¹⁶⁰Gd | (5−) | | |-id=Europium-160m | style="text-indent:1em" | ^160mEu | colspan="3" style="text-indent:2em" | 93.0(12)&nbsp;keV | 30.8(5)&nbsp;s | IT | ¹⁶⁰Eu | (1−) | | |-id=Europium-161 | ¹⁶¹Eu | style="text-align:right" | 63 | style="text-align:right" | 98 | 160.933664(11) | 26.2(23)&nbsp;s | β^− | ¹⁶¹Gd | 5/2+# | | |-id=Europium-162 | ¹⁶²Eu | style="text-align:right" | 63 | style="text-align:right" | 99 | 161.9369583(14) | ~10&nbsp;s | β^− | ¹⁶²Gd | 1+# | | |-id=Europium-162m | style="text-indent:1em" | ^162mEu | colspan="3" style="text-indent:2em" | 158.0(17)&nbsp;keV | 15.0(5)&nbsp;s | IT | ¹⁶²Eu | (6+) | | |-id=Europium-163 | ¹⁶³Eu | style="text-align:right" | 63 | style="text-align:right" | 100 | 162.93926551(97) | 7.7(4)&nbsp;s | β^− | ¹⁶³Gd | 5/2+# | | |-id=Europium-163m | style="text-indent:1em" | ^163mEu | colspan="3" style="text-indent:2em" | 964.5(5)&nbsp;keV | 911(24)&nbsp;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)&nbsp;s | β^− | ¹⁶⁴Gd | 3−# | | |-id=Europium-165 | ¹⁶⁵Eu | style="text-align:right" | 63 | style="text-align:right" | 102 | 164.9455401(56) | | 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| | β^− (99.37%) | ¹⁶⁶Gd | rowspan=2|0−# | rowspan=2| | 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| | β^− (98.05%) | ¹⁶⁷Gd | rowspan=2|5/2+# | rowspan=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| | β^− (96.05%) | ¹⁶⁸Gd | rowspan=2|6−# | rowspan=2| | 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| | β^− (85.38%) | ¹⁶⁹Gd | rowspan=2|5/2+# | rowspan=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| | β^− (>76%) | ¹⁷⁰Gd | rowspan=2| | rowspan=2| | rowspan=2| |- | β^−, n (<24%) | ¹⁶⁹Gd

Europium-155

Europium-155 is a fission product with a half-life of 4.742 years and has a maximum decay energy of 252 keV. Because of its position on the high-mass end of the yield curve, it has a low fission product yield, about 1 to 2% that of the most abundant fission products.

¹⁵⁵Eu's large neutron capture cross section means that most of 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 captures on ¹⁵³Eu and ¹⁵⁴Eu, whose direct fission yield is extremely small as its mass chain stops at ¹⁵⁴Sm. However, the high cross sections, and even higher for 155 than 154, mean that both ¹⁵⁵Eu and ¹⁵⁴Eu are destroyed faster than they are produced. See the table below for numeric details on this process.

See also

Daughter products other than europium

• Isotopes of gadolinium
• Isotopes of samarium
• Isotopes of promethium

References