Isotopes of europium

Isotopes of europium (63Eu)
Main isotopes[1] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
150Eu synth 36.9 y β+ 150Sm
151Eu 47.8% 4.6×1018 y α 147Pm
152Eu synth 13.517 y β+ 152Sm
β− 152Gd
153Eu 52.2% stable
154Eu synth 8.592 y β− 154Gd
ε 154Sm
155Eu synth 4.742 y β− 155Gd
Standard atomic weight Ar°(Eu)

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;[4][5] its measured half-life of 4.6 × 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


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][n 8] 		Spin and
parity[1]
[n 9][n 5] 		Natural abundance (mole fraction)
Excitation energy[n 5] Normal proportion[1] Range of variation
130Eu 63 67 129.96402(58)# 1.0(4) ms p 129Sm (1+)
131Eu 63 68 130.95763(43)# 17.8(19) ms p (89%) 130Sm 3/2+
β+ (?%) 131Sm
β+, p (?%) 130Pm
134Eu 63 71 133.94654(32)# 0.5(2) s β+ 134Sm
β+, p (?%) 133Pm
135Eu 63 72 134.94187(21)# 1.5(2) s β+ 135Sm 5/2+#
136Eu 63 73 135.93962(21)# 3.3(3) s β+ (99.91%) 136Sm 6+#
β+, p (0.09%) 135Pm
136mEu[n 10] 100(100)# keV 3.8(3) s β+ (99.91%) 136Sm 1+#
β+, p (0.09%) 135Pm
137Eu 63 74 136.9354307(47) 8.4(5) s β+ 137Sm 5/2+#
138Eu 63 75 137.933709(30) 5# s 2−#
138mEu[n 10] 100(50)# keV 12.1(6) s β+ 138Sm 7−#
139Eu 63 76 138.929792(14) 17.9(6) s β+ 139Sm (11/2)−
139mEu 148.3(3) keV 10(2) μs IT 139Eu (7/2+)
140Eu 63 77 139.928088(55) 1.51(2) s β+ (95.1%) 140Sm 1+
EC (4.9%)
140m1Eu 210(14) keV 125(2) ms IT (>99%) 140Eu (5−)
β+ (>1%) 140Sm
140m2Eu 669(14) keV 299.8(21) ns IT 140Eu (8+)
141Eu 63 78 140.924932(14) 40.7(7) s β+ 141Sm 5/2+
141mEu 96.45(7) keV 2.7(3) s IT (86%) 141Eu 11/2−
β+ (14%) 141Sm
142Eu 63 79 141.923447(32) 2.36(10) s β+ (89.9%) 142Sm 1+
EC (11.1%) 142Sm
142mEu 450(30) keV 1.223(8) min β+ 142Sm 8−
143Eu 63 80 142.920299(12) 2.59(2) min β+ 143Sm 5/2+
143mEu 389.51(4) keV 50.0(5) μs IT 143Eu 11/2−
144Eu 63 81 143.918819(12) 10.2(1) s β+ 144Sm 1+
144mEu 1127.6(6) keV 1.0(1) μs IT 144Eu 8−
145Eu 63 82 144.9162727(33) 5.93(4) d β+ 145Sm 5/2+
145mEu 716.0(3) keV 490(30) ns IT 145Eu 11/2−
146Eu 63 83 145.9172109(65) 4.61(3) d β+ 146Sm 4−
146mEu 666.33(11) keV 235(3) μs IT 146Eu 9+
147Eu 63 84 146.9167524(28) 24.1(6) d β+ 147Sm 5/2+
α (0.0022%) 143Pm
147mEu 625.27(5) keV 765(15) ns IT 147Eu 11/2−
148Eu 63 85 147.918091(11) 54.5(5) d β+ 148Sm 5−
α (9.4×10−7%) 144Pm
148mEu 720.4(3) keV 162(8) ns IT 148Eu 9+
149Eu 63 86 148.9179369(42) 93.1(4) d EC 149Sm 5/2+
149mEu 496.386(2) keV 2.45(5) μs IT 149Eu 11/2−
150Eu 63 87 149.9197071(67) 36.9(9) y β+ 150Sm 5−
150mEu 41.7(10) keV 12.8(1) h β− (89%) 150Gd 0−
β+ (11%) 150Sm
IT (<5×10−8%)[7] 150Eu
151Eu[n 11][n 12] 63 88 150.9198566(13) 4.6(12)×1018 y α 147Pm 5/2+ 0.4781(6)
151mEu 196.245(10) keV 58.9(5) μs IT 151Eu 11/2−
152Eu 63 89 151.9217510(13) 13.517(6) y β+ (72.08%) 152Sm 3−
β− (27.92%) 152Gd
152m1Eu 45.5998(4) keV 9.3116(13) h β− (73%) 152Gd 0−
β+ (27%) 152Sm
152m2Eu 65.2969(4) keV 940(80) ns IT 152Eu 1−
152m3Eu 78.2331(4) keV 165(10) ns IT 152Eu 1+
152m4Eu 89.8496(4) keV 384(10) ns IT 152Eu 4+
152m5Eu 147.86(10) keV 95.8(4) min IT 152Eu 8−
153Eu[n 11] 63 90 152.9212368(13) Observationally Stable[n 13][8][9] 5/2+ 0.5219(6)
153mEu 1771.0(4) keV 475(10) ns IT 153Eu 19/2−
154Eu[n 11] 63 91 153.9229857(13) 8.592(3) y β− (99.98%) 154Gd 3−
EC (0.02%) 154Sm
154m1Eu 68.1702(4) keV 2.2(1) μs IT 154Eu 2+
154m2Eu 145.3(3) keV 46.3(4) min IT 154Eu (8−)
155Eu[n 11] 63 92 154.9228998(13) 4.742(8) y β− 155Gd 5/2+
156Eu[n 11] 63 93 155.9247630(38) 15.19(8) d β− 156Gd 0+
157Eu 63 94 156.9254326(45) 15.18(3) h β− 157Gd 5/2+
158Eu 63 95 157.9277822(22) 45.9(2) min β− 158Gd 1−
159Eu 63 96 158.9290995(46) 18.1(1) min β− 159Gd 5/2+
160Eu 63 97 159.93183698(97) 42.6(5) s β− 160Gd (5−)
160mEu 93.0(12) keV 30.8(5) s IT 160Eu (1−)
161Eu 63 98 160.933664(11) 26.2(23) s β− 161Gd 5/2+#
162Eu 63 99 161.9369583(14) ~10 s β− 162Gd 1+#
162mEu 158.0(17) keV 15.0(5) s IT 162Eu (6+)
163Eu 63 100 162.93926551(97) 7.7(4) s β− 163Gd 5/2+#
163mEu 964.5(5) keV 911(24) ns IT 163Eu (13/2−)
164Eu 63 101 163.9428529(22) 4.16(19) s β− 164Gd 3−#
165Eu 63 102 164.9455401(56) 2.163+0.139
−0.120 s[10] 		β− 165Gd 5/2+#
166Eu 63 103 165.94981(11)# 1.277+0.100
−0.145 s[10] 		β− (99.37%) 166Gd 0−#
β−, n (0.63%) 165Gd
167Eu 63 104 166.95301(43)# 852+76
−54 ms[10] 		β− (98.05%) 167Gd 5/2+#
β−, n (1.95%) 166Gd
168Eu 63 105 167.95786(43)# 440+48
−47 ms[10] 		β− (96.05%) 168Gd 6−#
β−, n (3.95%) 167Gd
169Eu 63 106 168.96172(54)# 389+92
−88 ms[10] 		β− (85.38%) 169Gd 5/2+#
β−, n (14.62%) 168Gd
170Eu 63 107 169.96687(54)# 197+74
−71 ms[10] 		β− (>76%) 170Gd
β−, n (<24%) 169Gd
This table header & footer:
  1. ^ mEu – 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. ^ a b c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  6. ^ Modes of decay:
    α: Alpha decay
    β+: Positron emission
    EC: Electron capture
    β−: Beta decay
    IT: Isomeric transition


    p: Proton emission
  7. ^ Bold italics symbol as daughter – Daughter product is nearly stable.
  8. ^ Bold symbol as daughter – Daughter product is stable.
  9. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  10. ^ a b Order of ground state and isomer is uncertain.
  11. ^ a b c d e Fission product
  12. ^ Primordial radionuclide
  13. ^ Believed to undergo α decay to 149Pm with a half-life over 5.5×1017 years

Europium-155

Medium-lived fission products
Nuclide t1⁄2 Yield Q[a 1] βγ
(a) (%)[a 2] (keV)
155Eu  4.74   0.0803[a 3] 252 βγ
85Kr 10.73   0.2180[a 4] 687 βγ
113mCd 13.9    0.0008[a 3] 316 β
90Sr 28.91 4.505     2826[a 5] β
137Cs 30.04 6.337     1176 βγ
121mSn 43.9  0.00005   390 βγ
151Sm 94.6  0.5314[a 3] 77 β
  1. ^ Decay energy is split among β, neutrino, and γ if any.
  2. ^ Per 65 thermal neutron fissions of 235U and 35 of 239Pu.
  3. ^ a b c Neutron poison; in thermal reactors most is destroyed by further neutron capture.
  4. ^ Less than 1/4 of mass-85 fission products as most bypass ground state: Br-85 -> Kr-85m -> Rb-85.
  5. ^ Has decay energy 546 keV; its decay product Y-90 has decay energy 2.28 MeV with weak gamma branching.

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.

Isotope Half-life Relative yield (fission) Thermal neutron Resonance integral
Eu-153 Stable 5 350 1500
Eu-154 8.592 years ~0 1500 1600
Eu-155 4.742 years 1 3900 16000

See also

Daughter products other than europium

References

  1. ^ a b c d e Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3) 030001. doi:10.1088/1674-1137/abddae.
  2. ^ "Standard Atomic Weights: Europium". CIAAW. 1995.
  3. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ^ Belli, P.; et al. (2007). "Search for α decay of natural europium". Nuclear Physics A. 789 (1–4): 15–29. Bibcode:2007NuPhA.789...15B. doi:10.1016/j.nuclphysa.2007.03.001.
  5. ^ Casali, N.; Nagorny, S. S.; Orio, F.; Pattavina, L.; et al. (2014). "Discovery of the 151Eu α decay". Journal of Physics G: Nuclear and Particle Physics. 41 (7): 075101. arXiv:1311.2834. Bibcode:2014JPhG...41g5101C. doi:10.1088/0954-3899/41/7/075101. S2CID 116920467.{{cite journal}}: CS1 maint: article number as page number (link)
  6. ^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3) 030003. doi:10.1088/1674-1137/abddaf.
  7. ^ "Adopted Levels for 150Eu" (PDF). NNDC Chart of Nuclides.
  8. ^ Danevich, F. A.; Andreotti, E.; Hult, M.; Marissens, G.; Tretyak, V. I.; Yuksel, A. (2012). "Search for α decay of 151Eu to the first excited level of 147Pm using underground γ-ray spectrometry". European Physical Journal A. 48 (157): 157. arXiv:1301.3465. Bibcode:2012EPJA...48..157D. doi:10.1140/epja/i2012-12157-7. S2CID 118657922.
  9. ^ Belli, P.; Bernabei, R.; Danevich, F. A.; et al. (2019). "Experimental searches for rare alpha and beta decays". European Physical Journal A. 55 (8): 140–1–140–7. arXiv:1908.11458. Bibcode:2019EPJA...55..140B. doi:10.1140/epja/i2019-12823-2. ISSN 1434-601X. S2CID 201664098.
  10. ^ a b c d e f Kiss, G. G.; Vitéz-Sveiczer, A.; Saito, Y.; et al. (2022). "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". The Astrophysical Journal. 936 (107): 107. Bibcode:2022ApJ...936..107K. doi:10.3847/1538-4357/ac80fc. hdl:2117/375253.
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