Isotopes of samarium
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
talk |
---|
Naturally occurring
Other than the naturally occurring isotopes, the longest-lived radioisotopes are 151Sm, which has a half-life of 94.6 years,[7] and 145Sm, which has a half-life of 340 days. All of the remaining radioisotopes, which range from 129Sm to 168Sm, have half-lives that are less than two days, and the majority of these have half-lives that are less than 48 seconds. This element also has twelve known isomers with the most stable being 141mSm (t1/2 22.6 minutes), 143m1Sm (t1/2 66 seconds) and 139mSm (t1/2 10.7 seconds).
The long lived isotopes, 146Sm, 147Sm, and 148Sm, primarily decay by alpha decay to isotopes of neodymium. Lighter unstable isotopes of samarium primarily decay by electron capture to isotopes of promethium, while heavier ones decay by beta decay to isotopes of europium.
Isotopes of samarium are used in samarium–neodymium dating for determining the age relationships of rocks and meteorites.
151Sm is a
Samarium is theoretically the lightest element with even atomic number with no stable isotopes (all isotopes of it can theoretically go either alpha decay or beta decay or double beta decay), other such elements are those with atomic numbers > 66 (dysprosium, which is the heaviest theoretically stable nuclide).
List of isotopes
Nuclide [n 1] |
Z | N | Isotopic mass (Da) [n 2][n 3] |
Half-life [n 4][n 5] |
Daughter isotope [n 7][n 8] |
Natural abundance (mole fraction) | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy[n 5] | Normal proportion | Range of variation | |||||||||||||||||
129Sm | 62 | 67 | 128.95464(54)# | 550(100) ms | 5/2+# | ||||||||||||||
130Sm | 62 | 68 | 129.94892(43)# | 1# s | β+ | 130Pm | 0+ | ||||||||||||
131Sm | 62 | 69 | 130.94611(32)# | 1.2(2) s | β+ | 131Pm | 5/2+# | ||||||||||||
β+, p (rare) | 130Nd | ||||||||||||||||||
132Sm | 62 | 70 | 131.94069(32)# | 4.0(3) s | β+ | 132Pm | 0+ | ||||||||||||
β+, p | 131Nd | ||||||||||||||||||
133Sm | 62 | 71 | 132.93867(21)# | 2.90(17) s | β+ | 133Pm | (5/2+) | ||||||||||||
β+, p | 132Nd | ||||||||||||||||||
134Sm | 62 | 72 | 133.93397(21)# | 10(1) s | β+ | 134Pm | 0+ | ||||||||||||
135Sm | 62 | 73 | 134.93252(17) | 10.3(5) s | β+ (99.98%) | 135Pm | (7/2+) | ||||||||||||
β+, p (.02%) | 134Nd | ||||||||||||||||||
135mSm | 0(300)# keV | 2.4(9) s | β+ | 135Pm | (3/2+, 5/2+) | ||||||||||||||
136Sm | 62 | 74 | 135.928276(13) | 47(2) s | β+ | 136Pm | 0+ | ||||||||||||
136mSm | 2264.7(11) keV | 15(1) μs | (8−) | ||||||||||||||||
137Sm | 62 | 75 | 136.92697(5) | 45(1) s | β+ | 137Pm | (9/2−) | ||||||||||||
137mSm | 180(50)# keV | 20# s | β+ | 137Pm | 1/2+# | ||||||||||||||
138Sm | 62 | 76 | 137.923244(13) | 3.1(2) min | β+ | 138Pm | 0+ | ||||||||||||
139Sm | 62 | 77 | 138.922297(12) | 2.57(10) min | β+ | 139Pm | 1/2+ | ||||||||||||
139mSm | 457.40(22) keV | 10.7(6) s | IT (93.7%)
|
139Sm | 11/2− | ||||||||||||||
β+ (6.3%) | 139Pm | ||||||||||||||||||
140Sm | 62 | 78 | 139.918995(13) | 14.82(12) min | β+ | 140Pm | 0+ | ||||||||||||
141Sm | 62 | 79 | 140.918476(9) | 10.2(2) min | β+ | 141Pm | 1/2+ | ||||||||||||
141mSm | 176.0(3) keV | 22.6(2) min | β+ (99.69%) | 141Pm | 11/2− | ||||||||||||||
IT (.31%) | 141Sm | ||||||||||||||||||
142Sm | 62 | 80 | 141.915198(6) | 72.49(5) min | β+ | 142Pm | 0+ | ||||||||||||
143Sm | 62 | 81 | 142.914628(4) | 8.75(8) min | β+ | 143Pm | 3/2+ | ||||||||||||
143m1Sm | 753.99(16) keV | 66(2) s | IT (99.76%) | 143Sm | 11/2− | ||||||||||||||
β+ (.24%) | 143Pm | ||||||||||||||||||
143m2Sm | 2793.8(13) keV | 30(3) ms | 23/2(−) | ||||||||||||||||
144Sm | 62 | 82 | 143.911999(3) | Observationally stable[n 10]
|
0+ | 0.0307(7) | |||||||||||||
144mSm | 2323.60(8) keV | 880(25) ns | 6+ | ||||||||||||||||
145Sm | 62 | 83 | 144.913410(3) | 340(3) d | EC | 145Pm | 7/2− | ||||||||||||
145mSm | 8786.2(7) keV | 990(170) ns [0.96(+19−15) μs] |
(49/2+) | ||||||||||||||||
146Sm | 62 | 84 | 145.913041(4) | 1.03(5)×108 y[n 11] | α | 142Nd | 0+ | Trace | |||||||||||
147Sm[n 12][n 13][n 14] | 62 | 85 | 146.9148979(26) | (1.066±0.5)×1011 y | α | 143Nd | 7/2− | 0.1499(18) | |||||||||||
148Sm[n 12] | 62 | 86 | 147.9148227(26) | (6.3±1.3)×1015 y | α | 144Nd | 0+ | 0.1124(10) | |||||||||||
149Sm[n 13][n 15] | 62 | 87 | 148.9171847(26) | Observationally stable[n 16] | 7/2− | 0.1382(7) | |||||||||||||
150Sm | 62 | 88 | 149.9172755(26) | Observationally stable[n 17] | 0+ | 0.0738(1) | |||||||||||||
151Sm[n 13][n 15] | 62 | 89 | 150.9199324(26) | 94.6±0.6 y | β− | 151Eu | 5/2− | ||||||||||||
151mSm | 261.13(4) keV | 1.4(1) μs | (11/2)− | ||||||||||||||||
152Sm[n 13] | 62 | 90 | 151.9197324(27) | Observationally stable[n 18] | 0+ | 0.2675(16) | |||||||||||||
153Sm[n 13] | 62 | 91 | 152.9220974(27) | 46.2846±0.0023 h | β− | 153Eu | 3/2+ | ||||||||||||
153mSm | 98.37(10) keV | 10.6(3) ms | IT | 153Sm | 11/2− | ||||||||||||||
154Sm[n 13] | 62 | 92 | 153.9222093(27) | Observationally stable[n 19] | 0+ | 0.2275(29) | |||||||||||||
155Sm | 62 | 93 | 154.9246402(28) | 22.3(2) min | β− | 155Eu | 3/2− | ||||||||||||
156Sm | 62 | 94 | 155.925528(10) | 9.4(2) h | β− | 156Eu | 0+ | ||||||||||||
156mSm | 1397.55(9) keV | 185(7) ns | 5− | ||||||||||||||||
157Sm | 62 | 95 | 156.92836(5) | 8.03(7) min | β− | 157Eu | (3/2−) | ||||||||||||
158Sm | 62 | 96 | 157.92999(8) | 5.30(3) min | β− | 158Eu | 0+ | ||||||||||||
159Sm | 62 | 97 | 158.93321(11) | 11.37(15) s | β− | 159Eu | 5/2− | ||||||||||||
160Sm | 62 | 98 | 159.93514(21)# | 9.6(3) s | β− | 160Eu | 0+ | ||||||||||||
161Sm | 62 | 99 | 160.93883(32)# | 4.349+0.425 −0.441 s[9] |
β− | 161Eu | 7/2+# | ||||||||||||
162Sm | 62 | 100 | 161.94122(54)# | 3.369+0.200 −0.303 s[9] |
β− | 162Eu | 0+ | ||||||||||||
163Sm | 62 | 101 | 162.94536(75)# | 1.744+0.180 −0.204 s[9] |
β− | 163Eu | 1/2−# | ||||||||||||
164Sm | 62 | 102 | 163.94828(86)# | 1.422+0.54 −0.59 s[9] |
β− | 164Eu | 0+ | ||||||||||||
165Sm | 62 | 103 | 164.95298(97)# | 592+51 −55 ms[9] |
β− (98.64%) | 165Eu | 5/2−# | ||||||||||||
β−, n (1.36%) | 164Eu | ||||||||||||||||||
166Sm | 62 | 104 | 396+56 −63 ms[9] |
β− (95.62%) | 166Eu | 0+ | |||||||||||||
β−, n (4.38%) | 165Eu | ||||||||||||||||||
167Sm | 62 | 105 | 334+83 −78 ms[9] |
β− | 167Eu | ||||||||||||||
β−, n | 166Eu | ||||||||||||||||||
168Sm | 62 | 106 | 353+210 −164 ms[9] |
β− | 168Eu | 0+ | |||||||||||||
β−, n | 167Eu | ||||||||||||||||||
This table header & footer: |
- ^ mSm – Excited nuclear isomer.
- ^ ( ) – Uncertainty (1σ) 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).
- 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:
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.
- ^ Possibly undergoing β+β+ decay to 144Nd[1]
- ^ See retraction note above
- ^ radioisotope
- ^ Fission product
- ^ Used in Samarium–neodymium dating
- ^ a b Neutron poison in reactors
- ^ Believed to undergo α decay to 145Nd with a half-life over 2×1015 years[1][8]
- ^ Possibly to undergo α decay to 146Nd[8]
- ^ Possibly to undergo α decay to 148Nd[8]
- ^ Believed to undergo β−β− decay to 154Gd with a half-life over 2.3×1018 years[1]
Samarium-149
Samarium-149 (149Sm) is an observationally stable isotope of
The equilibrium concentration (and thus the poisoning effect) builds to an equilibrium value in about 500 hours (about 20 days) of reactor operation, and since 149Sm is stable, the concentration remains essentially constant during further reactor operation. This contrasts with
Samarium-151
t½ )
(year |
Yield (%) |
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 |
Thermal
|
Fast
|
14 MeV
| |
---|---|---|---|
232Th | not fissile | 0.399 ± 0.065 | 0.165 ± 0.035 |
233U | 0.333 ± 0.017 | 0.312 ± 0.014 | 0.49 ± 0.11 |
235U | 0.4204 ± 0.0071 | 0.431 ± 0.015 | 0.388 ± 0.061 |
238U | not fissile | 0.810 ± 0.012 | 0.800 ± 0.057 |
239Pu | 0.776 ± 0.018 | 0.797 ± 0.037 | ? |
241Pu | 0.86 ± 0.24 | 0.910 ± 0.025 | ? |
Samarium-151 (151Sm) has a half-life of 88.8 years, undergoing low-energy beta decay, and has a fission product yield of 0.4203% for thermal neutrons and 235U, about 39% of 149Sm's yield. The yield is somewhat higher for 239Pu.
Its
Since nuclear fuel is used for several years (burnup) in a nuclear power plant, the final amount of 151Sm in the spent nuclear fuel at discharge is only a small fraction of the total 151Sm produced during the use of the fuel. According to one study, the mass fraction of 151Sm in spent fuel is about 0.0025 for heavy loading of
Samarium-153
Samarium-153 (153Sm) has a half-life of 46.3 hours, undergoing β− decay into 153Eu. As a component of
References
- Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean;
- Isotopic compositions and standard atomic masses from:
- .
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". .
- "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;
- 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.). ISBN 978-0-8493-0485-9.
- ^ .
- ^ "Standard Atomic Weights: Samarium". CIAAW. 2005.
- ISSN 1365-3075.
- PMID 17124541.
- ^ S2CID 206538240.
- S2CID 236990856.. Retraction Watch. Retrieved 30 March 2023.
- Joelving, Frederik (30 March 2023). "One small error for a physicist, one giant blunder for planetary science"