Isotopes of europium

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Naturally occurring europium (Eu) is composed of 2 isotopes, 151Eu and 153Eu, with 153Eu being the most abundant (52.2% natural abundance). While 153Eu is stable, 151Eu was recently found to be unstable and to undergo alpha decay with half-life of (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 y.[1] Besides 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, and 154Eu with a half-life of 8.593 years. All of the remaining radioactive isotopes have half-lives that are less than 4.7612 years, and the majority of these have half-lives that are less than 12.2 seconds. This element also has 17 meta states, with the most stable being 150mEu (t1/2 12.8 hours), 152m1Eu (t1/2 9.3116 hours) and 152m2Eu (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 minus decay. The primary decay products before 153Eu are isotopes of samarium and the primary products after are isotopes of gadolinium.

Standard atomic mass: 151.964(1) u.

Europium-155[edit]

Medium-lived
fission products
Prop:
Unit:
t½
(a)
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 96.6 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 halflife are all far less than 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.[2]

Isotope Halflife 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

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life[n 1] decay
mode(s)[3][n 2]
daughter
isotope(s)[n 3]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
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+ 140Sm 1+
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+ 142Sm 1+
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) a 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 4] 63 88 150.9198502(26) 4.62×1018 a 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) a EC (72.09%), β+ (0.027%) 152Sm 3-
β- (27.9%) 152Gd
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 5] 63 90 152.9212303(26) Observationally Stable[n 6] 5/2+ 0.5219(6)
154Eu[n 5] 63 91 153.9229792(26) 8.593(4) a β- (99.98%) 154Gd 3-
EC (.02%) 154Sm
154m1Eu 145.3(3) keV 46.3(4) min IT 154Eu (8-)
154m2Eu 68.1702(4) keV 2.2(1) µs 2+
155Eu[n 5] 63 92 154.9228933(27) 4.7611(13) a β- 155Gd 5/2+
156Eu[n 5] 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)# 6# s β- 163Gd 5/2+#
164Eu 63 101 163.94299(64)# 2# s β- 164Gd
165Eu 63 102 164.94572(75)# 1# s β- 165Gd 5/2+#
166Eu 63 103 165.94997(86)# 400# ms β- 166Gd
167Eu 63 104 166.95321(86)# 200# ms β- 167Gd 5/2+#
  1. ^ Bold for isotopes with half-lives longer than the age of the universe (nearly stable)
  2. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  3. ^ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
  4. ^ primordial radionuclide
  5. ^ a b c d Fission product
  6. ^ Believed to undergo α decay to 149Pm

Notes[edit]

  • Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References[edit]

  1. ^ N. Casali, SS. Nagorny, F. Orio, L. Pattavina et al. (2014). "Discovery of the 151Eu α decay". Journal of Physics G: Nuclear and Particle Physics 41: 075101. doi:10.1088/0954-3899/41/7/075101. 
  2. ^ http://www-nds.ipen.br/sgnucdat/b2.pdf
  3. ^ http://www.nucleonica.net/unc.aspx


Isotopes of samarium Isotopes of europium Isotopes of gadolinium
Table of nuclides