Isotopes of europium

Isotopes of europium (₆₃Eu)
βべーた−	152Gd
Standard atomic weight Ar°(Eu)
	151.964±0.001; 151.96±0.01 (abridged);
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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 (t_1/2 12.8 hours), ^152m1Eu (t_1/2 9.3116 hours) and ^152m5Eu (t_1/2 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[edit]

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)
Nuclide ^{[n 1]}	Excitation energy^{[n 5]}			Half-life ^{[n 4]}^{[n 5]}	Decay mode ^{[n 6]}	Daughter isotope ^{[n 7]}^{[n 8]}	Spin and parity ^{[n 9]}^{[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べーた⁺	¹³²Sm
¹³²Eu	63	69	131.95437(43)#	100# ms	p	¹³¹Sm
¹³³Eu	63	70	132.94924(32)#	200# ms	βべーた⁺	¹³³Sm	11/2−#
¹³⁴Eu	63	71	133.94651(21)#	0.5(2) s	βべーた⁺	¹³⁴Sm
¹³⁴Eu	63	71	133.94651(21)#	0.5(2) s	βべーた⁺, p (rare)	¹³³Pm
¹³⁵Eu	63	72	134.94182(32)#	1.5(2) s	βべーた⁺	¹³⁵Sm	11/2−#
¹³⁵Eu	63	72	134.94182(32)#	1.5(2) s	βべーた⁺, p	¹³⁴Pm	11/2−#
¹³⁶Eu	63	73	135.93960(21)#	3.3(3) s	βべーた⁺ (99.91%)	¹³⁶Sm	(7+)
¹³⁶Eu	63	73	135.93960(21)#	3.3(3) s	βべーた⁺, p (.09%)	¹³⁵Pm	(7+)
^136mEu	0(500)# keV			3.8(3) s	βべーた⁺ (99.91%)	¹³⁶Sm	(3+)
^136mEu	0(500)# keV			3.8(3) s	βべーた⁺, p (.09%)	¹³⁵Pm	(3+)
¹³⁷Eu	63	74	136.93557(21)#	8.4(5) s	βべーた⁺	¹³⁷Sm	11/2−#
¹³⁸Eu	63	75	137.93371(3)	12.1(6) s	βべーた⁺	¹³⁸Sm	(6−)
¹³⁹Eu	63	76	138.929792(14)	17.9(6) s	βべーた⁺	¹³⁹Sm	(11/2)−
¹⁴⁰Eu	63	77	139.92809(6)	1.51(2) s	βべーた⁺ (95.1(7)%)	¹⁴⁰Sm	1+
¹⁴⁰Eu	63	77	139.92809(6)	1.51(2) s	EC (4.9(7)%)	¹⁴⁰Sm	1+
^140mEu	210(15) keV			125(2) ms	IT (99%)	¹⁴⁰Eu	5−#
^140mEu	210(15) keV			125(2) ms	βべーた⁺(1%)	¹⁴⁰Sm	5−#
¹⁴¹Eu	63	78	140.924931(14)	40.7(7) s	βべーた⁺	¹⁴¹Sm	5/2+
^141mEu	96.45(7) keV			2.7(3) s	IT (86%)	¹⁴¹Eu	11/2−
^141mEu	96.45(7) keV			2.7(3) s	βべーた⁺ (14%)	¹⁴¹Sm	11/2−
¹⁴²Eu	63	79	141.92343(3)	2.36(10) s	βべーた⁺ (89.9(16)%)	¹⁴²Sm	1+
¹⁴²Eu	63	79	141.92343(3)	2.36(10) s	EC (11.1(16)%)	¹⁴²Sm	1+
^142mEu	460(30) keV			1.223(8) min	βべーた⁺	¹⁴²Sm	8−
¹⁴³Eu	63	80	142.920298(12)	2.59(2) min	βべーた⁺	¹⁴³Sm	5/2+
^143mEu	389.51(4) keV			50.0(5) μみゅーs			11/2−
¹⁴⁴Eu	63	81	143.918817(12)	10.2(1) s	βべーた⁺	¹⁴⁴Sm	1+
^144mEu	1127.6(6) keV			1.0(1) μみゅーs			(8−)
¹⁴⁵Eu	63	82	144.916265(4)	5.93(4) d	βべーた⁺	¹⁴⁵Sm	5/2+
^145mEu	716.0(3) keV			490 ns			11/2−
¹⁴⁶Eu	63	83	145.917206(7)	4.61(3) d	βべーた⁺	¹⁴⁶Sm	4−
^146mEu	666.37(16) keV			235(3) μみゅーs			9+
¹⁴⁷Eu	63	84	146.916746(3)	24.1(6) d	βべーた⁺ (99.99%)	¹⁴⁷Sm	5/2+
¹⁴⁷Eu	63	84	146.916746(3)	24.1(6) d	αあるふぁ (.0022%)	¹⁴³Pm	5/2+
¹⁴⁸Eu	63	85	147.918086(11)	54.5(5) d	βべーた⁺ (100%)	¹⁴⁸Sm	5−
¹⁴⁸Eu	63	85	147.918086(11)	54.5(5) d	αあるふぁ (9.39×10⁻⁷%)	¹⁴⁴Pm	5−
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べーた⁺	¹⁵⁰Sm	5(−)
^150mEu	42.1(5) keV			12.8(1) h	βべーた⁻ (89%)	¹⁵⁰Gd	0−
					βべーた⁺ (11%)	¹⁵⁰Sm
					IT (5×10⁻⁸%)	¹⁵⁰Eu
¹⁵¹Eu^{[n 10]}	63	88	150.9198502(26)	4.62×10¹⁸ y	αあるふぁ	¹⁴⁷Pm	5/2+	0.4781(6)
^151mEu	196.245(10) keV			58.9(5) μみゅーs			11/2−
¹⁵²Eu	63	89	151.9217445(26)	13.537(6) y	EC (72.09%)	¹⁵²Sm	3−
					βべーた⁻ (27.9%)	¹⁵²Gd
					βべーた⁺ (0.027%)	¹⁵²Sm
^152m1Eu	45.5998(4) keV			9.3116(13) h	βべーた⁻ (72%)	¹⁵²Gd	0−
^152m1Eu	45.5998(4) keV			9.3116(13) h	βべーた⁺ (28%)	¹⁵²Sm	0−
^152m2Eu	65.2969(4) keV			0.94(8) μみゅーs			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べーた⁻ (99.98%)	¹⁵⁴Gd	3−
¹⁵⁴Eu^{[n 11]}	63	91	153.9229792(26)	8.593(4) y	EC (.02%)	¹⁵⁴Sm	3−
^154m1Eu	68.1702(4) keV			2.2(1) μみゅーs	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べーた⁻	¹⁵⁵Gd	5/2+
¹⁵⁶Eu^{[n 11]}	63	93	155.924752(6)	15.19(8) d	βべーた⁻	¹⁵⁶Gd	0+
¹⁵⁷Eu	63	94	156.925424(6)	15.18(3) h	βべーた⁻	¹⁵⁷Gd	5/2+
¹⁵⁸Eu	63	95	157.92785(8)	45.9(2) min	βべーた⁻	¹⁵⁸Gd	(1−)
¹⁵⁹Eu	63	96	158.929089(8)	18.1(1) min	βべーた⁻	¹⁵⁹Gd	5/2+
¹⁶⁰Eu	63	97	159.93197(22)#	38(4) s	βべーた⁻	¹⁶⁰Gd	1(−)
¹⁶¹Eu	63	98	160.93368(32)#	26(3) s	βべーた⁻	¹⁶¹Gd	5/2+#
¹⁶²Eu	63	99	161.93704(32)#	10.6(10) s	βべーた⁻	¹⁶²Gd
¹⁶³Eu	63	100	162.93921(54)#	7.7(4) s	βべーた⁻	¹⁶³Gd	5/2+#
^163mEu	964.5(10) keV			911(24) ns			(13/2−)
¹⁶⁴Eu	63	101	163.94299(64)#	4.16(19) s	βべーた⁻	¹⁶⁴Gd
¹⁶⁵Eu	63	102	164.94572(75)#	2.163+0.139 −0.120 s^[7]	βべーた⁻	¹⁶⁵Gd	5/2+#
¹⁶⁶Eu	63	103	165.94997(86)#	1.277+0.100 −0.145 s^[7]	βべーた⁻ (99.37%)	¹⁶⁶Gd
¹⁶⁶Eu	63	103	165.94997(86)#	1.277+0.100 −0.145 s^[7]	βべーた⁻, n (0.63%)	¹⁶⁵Gd
¹⁶⁷Eu	63	104	166.95321(86)#	852+76 −54 s^[7]	βべーた⁻ (98.05%)	¹⁶⁷Gd	5/2+#
¹⁶⁷Eu	63	104	166.95321(86)#	852+76 −54 s^[7]	βべーた⁻, n (1.95%)	¹⁶⁶Gd	5/2+#
¹⁶⁸Eu	63	105		440+48 −47 s^[7]	βべーた⁻ (96.05%)	¹⁶⁸Gd
¹⁶⁸Eu	63	105		440+48 −47 s^[7]	βべーた⁻, n (3.95%)	¹⁶⁷Gd
¹⁶⁹Eu	63	106		389+92 −88 s^[7]	βべーた⁻ (85.38%)	¹⁶⁹Gd
¹⁶⁹Eu	63	106		389+92 −88 s^[7]	βべーた⁻, n (14.62%)	¹⁶⁸Gd
¹⁷⁰Eu	63	107		197+74 −71 s^[7]	βべーた⁻	¹⁷⁰Gd
¹⁷⁰Eu	63	107		197+74 −71 s^[7]	βべーた⁻, n	¹⁶⁹Gd
This table header & footer: view

^ ^mEu – Excited nuclear isomer.
^ ( ) – Uncertainty (1σしぐま) is given in concise form in parentheses after the corresponding last digits.
^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^ Bold half-life – nearly stable, half-life longer than age of universe.
^ ^a ^b ^c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Modes of decay:

EC: Electron capture

IT: Isomeric transition

p: Proton emission
^ Bold italics symbol as daughter – Daughter product is nearly stable.
^ Bold symbol as daughter – Daughter product is stable.
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ primordial radionuclide
^ ^a ^b ^c ^d Fission product
^ Believed to undergo αあるふぁ decay to ¹⁴⁹Pm with a half-life over 5.5×10¹⁷ years

Europium-155[edit]

Medium-lived
fission products ^{[further explanation needed]}
	t_½ (year)	Yield (%)	Q (keV)	βべーたγがんま
¹⁵⁵Eu	4.76	0.0803	252	βべーたγがんま
⁸⁵Kr	10.76	0.2180	687	βべーたγがんま
^113mCd	14.1	0.0008	316	βべーた
⁹⁰Sr	28.9	4.505	2826	βべーた
¹³⁷Cs	30.23	6.337	1176	βべーたγがんま
^121mSn	43.9	0.00005	390	βべーたγがんま
¹⁵¹Sm	88.8	0.5314	77	βべーた

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[edit]

^ 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.
^ "Standard Atomic Weights: Europium". CIAAW. 1995.
^ 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.
^ Belli, P.; et al. (2007). "Search for αあるふぁ decay of natural europium". Nuclear Physics A. 789 (1–4): 15–29. Bibcode:2007NuPhA.789...15B. doi:10.1016/j.nuclphysa.2007.03.001.
^ Casali, N.; Nagorny, S. S.; Orio, F.; Pattavina, L.; et al. (2014). "Discovery of the ¹⁵¹Eu αあるふぁ 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.
^ Danevich, F. A.; Andreotti, E.; Hult, M.; Marissens, G.; Tretyak, V. I.; Yuksel, A. (2012). "Search for αあるふぁ decay of ¹⁵¹Eu to the first excited level of ¹⁴⁷Pm using underground γがんま-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.
^ ^a ^b ^c ^d ^e ^f Kiss, G. G.; Vitéz-Sveiczer, A.; Saito, Y.; et al. (2022). "Measuring the βべーた-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.
^ "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)

Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
Isotopic compositions and standard atomic masses from:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

[6] Eu – Excited nuclear isomer.

[7] ( ) – Uncertainty (1σしぐま) is given in concise form in parentheses after the corresponding last digits.

[TMS-8] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[9] Bold half-life – nearly stable, half-life longer than age of universe.

[TNN-10] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[11] Modes of decay:

EC: Electron capture

IT: Isomeric transition

p: Proton emission

[12] Bold italics symbol as daughter – Daughter product is nearly stable.

[13] Bold symbol as daughter – Daughter product is stable.

[14] ( ) spin value – Indicates spin with weak assignment arguments.

[15] rimordial radionuclide

[FP-16] Fission product

[n12-17] Believed to undergo αあるふぁ decay to ¹⁴⁹Pm with a half-life over 5.5×10¹⁷ years

[NUBASE2020-1] 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.

[CIAAW2021-3] 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.

[151Eu-Belli-4] Belli, P.; et al. (2007). "Search for αあるふぁ decay of natural europium". Nuclear Physics A. 789 (1–4): 15–29. Bibcode:2007NuPhA.789...15B. doi:10.1016/j.nuclphysa.2007.03.001.

[154Eu--5] Casali, N.; Nagorny, S. S.; Orio, F.; Pattavina, L.; et al. (2014). "Discovery of the ¹⁵¹Eu αあるふぁ 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.

[18] Danevich, F. A.; Andreotti, E.; Hult, M.; Marissens, G.; Tretyak, V. I.; Yuksel, A. (2012). "Search for αあるふぁ decay of ¹⁵¹Eu to the first excited level of ¹⁴⁷Pm using underground γがんま-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.

[Ln922-19] ^ ^a ^b ^c ^d ^e ^f Kiss, G. G.; Vitéz-Sveiczer, A.; Saito, Y.; et al. (2022). "Measuring the βべーた-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.

[154Eu-nds.ipen.br2011-20] "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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