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Isotopes of europium

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Isotopes of europium (63Eu)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
150Eu synth 36.9 y β+ 150Sm
151Eu 47.8% 4.62×1018 y α 147Pm
152Eu synth 13.54 y ε 152Sm
β− 152Gd
153Eu 52.2% stable
154Eu synth 8.59 y β− 154Gd
155Eu synth 4.76 y β− 155Gd
Standard atomic weight Ar°(Eu)

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.[4] The half-life is measured to be (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 years[5] 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 (t1/2 12.8 hours), 152m1Eu (t1/2 9.3116 hours) and 152m5Eu (t1/2 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

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Nuclide
[n 1] 		Z N Isotopic mass (Da)
[n 2][n 3] 		Half-life
[n 4][n 5] 		Decay
mode
[n 6] 		Daughter
isotope
[n 7][n 8] 		Spin and
parity
[n 9][n 5] 		Natural abundance (mole fraction)
Excitation energy[n 5] Normal proportion Range of variation
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
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
β+, p (rare) 133Pm
135Eu 63 72 134.94182(32)# 1.5(2) s β+ 135Sm 11/2−#
β+, p 134Pm
136Eu 63 73 135.93960(21)# 3.3(3) s β+ (99.91%) 136Sm (7+)
β+, p (.09%) 135Pm
136mEu 0(500)# keV 3.8(3) s β+ (99.91%) 136Sm (3+)
β+, p (.09%) 135Pm
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+ (95.1(7)%) 140Sm 1+
EC (4.9(7)%)
140mEu 210(15) keV 125(2) ms IT (99%) 140Eu 5−#
β+(1%) 140Sm
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−
β+ (14%) 141Sm
142Eu 63 79 141.92343(3) 2.36(10) s β+ (89.9(16)%) 142Sm 1+
EC (11.1(16)%)
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+
α (.0022%) 143Pm
148Eu 63 85 147.918086(11) 54.5(5) d β+ (100%) 148Sm 5−
α (9.39×10−7%) 144Pm
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 10] 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%) 152Sm 3−
β− (27.9%) 152Gd
β+ (0.027%) 152Sm
152m1Eu 45.5998(4) keV 9.3116(13) h β− (72%) 152Gd 0−
β+ (28%) 152Sm
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 11] 63 90 152.9212303(26) Observationally Stable[n 12][6] 5/2+ 0.5219(6)
154Eu[n 11] 63 91 153.9229792(26) 8.593(4) y β− (99.98%) 154Gd 3−
EC (.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 92 154.9228933(27) 4.7611(13) y β− 155Gd 5/2+
156Eu[n 11] 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)# 7.7(4) s β− 163Gd 5/2+#
163mEu 964.5(10) keV 911(24) ns (13/2−)
164Eu 63 101 163.94299(64)# 4.16(19) s β− 164Gd
165Eu 63 102 164.94572(75)# 2.163+0.139
−0.120 s[7] 		β− 165Gd 5/2+#
166Eu 63 103 165.94997(86)# 1.277+0.100
−0.145 s[7] 		β− (99.37%) 166Gd
β−, n (0.63%) 165Gd
167Eu 63 104 166.95321(86)# 852+76
−54 s[7] 		β− (98.05%) 167Gd 5/2+#
β−, n (1.95%) 166Gd
168Eu 63 105 440+48
−47 s[7] 		β− (96.05%) 168Gd
β−, n (3.95%) 167Gd
169Eu 63 106 389+92
−88 s[7] 		β− (85.38%) 169Gd
β−, n (14.62%) 168Gd
170Eu 63 107 197+74
−71 s[7] 		β− 170Gd
β−, n 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:
    EC: Electron capture
    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. ^ primordial radionuclide
  11. ^ a b c d Fission product
  12. ^ Believed to undergo α decay to 149Pm with a half-life over 5.5×1017 years

Europium-155

[edit]
Medium-lived
fission products [further explanation needed]
t½
(year) 		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 88.8  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 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.[8]

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

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  1. ^ 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.
  6. ^ 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.
  7. ^ 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.
  8. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2011-07-06. Retrieved 2011-04-02.{{cite web}}: CS1 maint: archived copy as title (link)
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