Isotopes of samarium

{{Short description|none}} {{Infobox samarium isotopes}} Naturally occurring samarium (₆₂Sm) is composed of five stable isotopes, ¹⁴⁴Sm, ¹⁴⁹Sm, ¹⁵⁰Sm, ¹⁵²Sm and ¹⁵⁴Sm, and two extremely long-lived radioisotopes, ¹⁴⁷Sm (half life: 1.066{{e|11}}&nbsp;y) and ¹⁴⁸Sm (6.3{{e|15}}&nbsp;y), with ¹⁵²Sm being the most abundant (26.75% natural abundance). ¹⁴⁶Sm (9.20{{e|7}}&nbsp;y)<ref name=Chiera2024 /> is also fairly long-lived, but is not long-lived enough to have survived in significant quantities from the formation of the Solar System on Earth, although it remains useful in radiometric dating in the Solar System as an extinct radionuclide.<ref>{{cite journal | title = Separation of samarium and neodymium: a prerequisite for getting signals from nuclear synthesis | author = Samir Maji | journal = Analyst | volume = 131 | pages = 1332–1334 | year = 2006 | doi = 10.1039/b608157f | pmid = 17124541 | issue = 12 | bibcode=2006Ana...131.1332M | display-authors = 1 | last2 = Lahiri | first2 = Susanta | last3 = Wierczinski | first3 = Birgit | last4 = Korschinek | first4 = Gunther}}</ref> It is the longest-lived nuclide that has not yet been confirmed to be primordial. Its instability is due to having 84 neutrons (two more than 82, which is a magic number corresponding to a stable neutron configuration), and so it may emit an alpha particle (which has 2 neutrons) to form neodymium-142 with 82 neutrons.

Other than those, the longest-lived radioisotopes are ¹⁵¹Sm, which has a half-life of 94.6 years,<ref>{{Cite journal | last1 = He | first1 = M. | last2 = Shen | first2 = H. | last3 = Shi | first3 = G. | last4 = Yin | first4 = X. | last5 = Tian | first5 = W. | last6 = Jiang | first6 = S. | doi = 10.1103/PhysRevC.80.064305 | title = Half-life of ¹⁵¹Sm remeasured | journal = Physical Review C | volume = 80 | issue = 6 | year = 2009 | article-number = 064305 |bibcode = 2009PhRvC..80f4305H }}</ref> 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. The most stable of the known isomers is ^141mSm (half-life 22.6 minutes).

The long-lived isotopes, ¹⁴⁶Sm, ¹⁴⁷Sm, and ¹⁴⁸Sm, decay by alpha emission 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. A 2012 paper<ref name="retracted2012">{{cite journal|last1=Kinoshita|first1=N.|last2=Paul|first2=M.|last3=Kashiv|first3=Y.|last4=Collon|first4=P.|last5=Deibel|first5=C. M.|last6=DiGiovine|first6=B.|last7=Greene|first7=J. P.|last8=Henderson|first8=D. J.|last9=Jiang|first9=C. L.|last10=Marley|first10=S. T.|last11=Nakanishi|first11=T.|last12=Pardo|first12=R. C.|last13=Rehm|first13=K. E.|last14=Robertson|first14=D.|last15=Scott|first15=R.|last16=Schmitt|first16=C.|last17=Tang|first17=X. D.|last18=Vondrasek|first18=R.|last19=Yokoyama|first19=A.|title=A Shorter 146Sm Half-Life Measured and Implications for 146Sm-142Nd Chronology in the Solar System|journal=Science|date=30 March 2012|volume=335|issue=6076|pages=1614–1617|doi=10.1126/science.1215510|pmid=22461609|language=en|issn=0036-8075|arxiv=1109.4805|bibcode=2012Sci...335.1614K|s2cid=206538240 }}{{Retracted|doi=10.1126/science.adh7739|pmid=36996231|https://retractionwatch.com/2023/03/30/one-small-error-for-a-physicist-one-giant-blunder-for-planetary-science/ ''Retraction Watch''|intentional=yes}}</ref> {{anchor|retnote}}<!-- referenced below--> revising the estimated half-life of ¹⁴⁶Sm from 10.3(5)×10⁷&nbsp;y to 6.8(7)×10⁷&nbsp;y was retracted (due to an experimental mistake) in 2023,<ref name="retracted2012"/><ref>{{multiref| {{cite journal |last1=Kinoshita |first1=N. |last2=Paul |first2=M. |last3=Kashiv |first3=Y. |last4=Collon |first4=P. |last5=Deibel |first5=C. M. |last6=DiGiovine |first6=B. |last7=Greene |first7=J. P. |last8=Jiang |first8=C. L. |last9=Marley |first9=S. T. |last10=Pardo |first10=R. C. |last11=Rehm |first11=K. E. |last12=Robertson |first12=D. |last13=Scott |first13=R. |last14=Schmitt |first14=C. |last15=Tang |first15=X. D. |last16=Vondrasek |first16=R. |last17=Yokoyama |first17=A. |title=Retraction |journal=Science |date=30 March 2023 |volume=379 |issue=6639 |page=1307 |doi=10.1126/science.adh7739 |pmid=36996231 |bibcode=2023Sci...379.1307K |s2cid=236990856 |doi-access=free }}| {{cite web |last1=Joelving |first1=Frederik |title=One small error for a physicist, one giant blunder for planetary science |url=https://retractionwatch.com/2023/03/30/one-small-error-for-a-physicist-one-giant-blunder-for-planetary-science/ |website=Retraction Watch |access-date=30 March 2023 |date=30 March 2023}} }}</ref> and the current, more accurate, value published subsequently.

The isotope ¹⁴⁷Sm is used in samarium–neodymium dating and as mentioned the extinct ¹⁴⁶Sm can also be used for dating.

¹⁵¹Sm is a medium-lived fission product and acts as a neutron poison in the nuclear fuel cycle. The stable fission product ¹⁴⁹Sm is also a neutron poison.

Samarium is the lightest element with even atomic number with no theoretically stable isotopes (all isotopes of it can energetically decay by the alpha, beta, or double-beta modes); other such elements are those with atomic numbers > 66 (dysprosium, which has the heaviest theoretically stable nuclide, ¹⁶⁴Dy).

== List of isotopes == {{Anchor|Samarium-135m|Samarium-137m}}

<!--Please delete anchor(s) from the list above or table below if adding a dedicated isotope section(s).-->

{{Isotopes table | symbol = Sm | refs = NUBASE2020, AME2020 II,<!-- updated 2025-02-16 --> IsotopeFRIB, IsomerFRIB | notes = m, unc(), mass#, exen#, hl#, hl-nst, spin(), spin#, p, IT, daughter-st, daughter-nst, discoveryname }} |-id=Samarium-128 | ¹²⁸Sm<ref name="suzuki2025">{{cite journal |last1=Suzuki |first1=H |last2=Fukuda |first2=N |last3=Takeda |first3=H |last4=Shimizu |first4=Y |last5=Yoshimoto |first5=M |last6=Togano |first6=Y |last7=Sato |first7=H |last8=Kitamura |first8=N |last9=Hanai |first9=S |last10=Momota |first10=S |last11=Kusaka |first11=K |last12=Yanagisawa |first12=Y |last13=Ohtake |first13=M |last14=Sumikama |first14=T |last15=Fukunishi |first15=N |last16=Michimasa |first16=S |title=Discovery of Proton-Rich Radioactive Isotopes in the Z = 60 Region Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 238U Beam |journal=Progress of Theoretical and Experimental Physics |date=7 November 2025 |volume=2025 |issue=11 |doi=10.1093/ptep/ptaf149|doi-access=free }}</ref> | style="text-align:right" | 62 | style="text-align:right" | 66 | 127.95797(54)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/128.pdf 2025] | 500#&nbsp;ms<br>[>310&nbsp;ns] | | | 0+ | | |-id=Samarium-129 | rowspan=2|¹²⁹Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 67 | rowspan=2|128.95456(54)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/129.pdf 1999] | rowspan=2|550(100)&nbsp;ms | β⁺ (?%) | ¹²⁹Pm | rowspan=2|(1/2+,3/2+) | rowspan=2| | rowspan=2| |- | β⁺, p (?%) | ¹²⁸Nd |-id=Samarium-130 | ¹³⁰Sm | style="text-align:right" | 62 | style="text-align:right" | 68 | 129.94879(43)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/130.pdf 1999] | 1#&nbsp;s | | | 0+ | | |-id=Samarium-131 | rowspan=2|¹³¹Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 69 | rowspan=2|130.94602(43)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/131.pdf 1986] | rowspan=2|1.2(2)&nbsp;s | β⁺ | ¹³¹Pm | rowspan=2|5/2+# | rowspan=2| | rowspan=2| |- | β⁺, p (?%) | ¹³⁰Nd |-id=Samarium-132 | ¹³²Sm | style="text-align:right" | 62 | style="text-align:right" | 70 | 131.94081(32)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/132.pdf 1989] | 4.0(3)&nbsp;s | β⁺ | ¹³²Pm | 0+ | | |-id=Samarium-133 | rowspan=2|¹³³Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 71 | rowspan=2|132.93856(32)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/133.pdf 1977] | rowspan=2|2.89(16)&nbsp;s | β⁺ (?%) | ¹³³Pm | rowspan=2|(5/2+) | rowspan=2| | rowspan=2| |- | β⁺, p (?%) | ¹³²Nd |-id=Samarium-133m | style="text-indent:1em" | ^133mSm | colspan="3" style="text-indent:2em" | 120(60)#&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/133Sm-1.pdf 2001] | 3.5(4)&nbsp;s | β⁺ | ¹³³Pm | (1/2−) | | |-id=Samarium-134 | ¹³⁴Sm | style="text-align:right" | 62 | style="text-align:right" | 72 | 133.93411(21)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/134.pdf 1977] | 9.5(8)&nbsp;s | β⁺ | ¹³⁴Pm | 0+ | | |-id=Samarium-135 | rowspan=2|¹³⁵Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 73 | rowspan=2|134.93252(17) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/135.pdf 1977] | rowspan=2|10.3(5)&nbsp;s | β⁺ (99.98%) | ¹³⁵Pm | rowspan=2|(7/2+) | rowspan=2| | rowspan=2| |- | β⁺, p (0.02%) | ¹³⁴Nd |-id=Samarium-136 | ¹³⁶Sm | style="text-align:right" | 62 | style="text-align:right" | 74 | 135.928276(13) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/136.pdf 1982] | 47(2)&nbsp;s | β⁺ | ¹³⁶Pm | 0+ | | |-id=Samarium-136m | style="text-indent:1em" | ^136mSm | colspan="3" style="text-indent:2em" | 2264.7(11)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/136Sm-1.pdf 1994] | 15(1)&nbsp;μs | IT | ¹³⁶Sm | (8−) | | |-id=Samarium-137 | ¹³⁷Sm | style="text-align:right" | 62 | style="text-align:right" | 75 | 136.927008(31) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/137.pdf 1986] | 45(1)&nbsp;s | β⁺ | ¹³⁷Pm | (9/2−) | | |-id=Samarium-138 | ¹³⁸Sm | style="text-align:right" | 62 | style="text-align:right" | 76 | 137.923244(13) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/138.pdf 1982] | 3.1(2)&nbsp;min | β⁺ | ¹³⁸Pm | 0+ | | |-id=Samarium-139 | ¹³⁹Sm | style="text-align:right" | 62 | style="text-align:right" | 77 | 138.922297(12) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/139.pdf 1971] | 2.57(10)&nbsp;min | β⁺ | ¹³⁹Pm | 1/2+ | | |-id=Samarium-139m | rowspan=2 style="text-indent:1em" | ^139mSm | rowspan=2 colspan="3" style="text-indent:2em" | 457.38(23)&nbsp;keV | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/139Sm-1.pdf 1975] | rowspan=2|10.7(6)&nbsp;s | IT (93.7%) | ¹³⁹Sm | rowspan=2|11/2− | rowspan=2| | rowspan=2| |- | β⁺ (6.3%) | ¹³⁹Pm |-id=Samarium-140 | ¹⁴⁰Sm | style="text-align:right" | 62 | style="text-align:right" | 78 | 139.918995(13) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/140.pdf 1967] | 14.82(12)&nbsp;min | β⁺ | ¹⁴⁰Pm | 0+ | | |-id=Samarium-141 | ¹⁴¹Sm | style="text-align:right" | 62 | style="text-align:right" | 79 | 140.9184815(92) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/141.pdf 1967] | 10.2(2)&nbsp;min | β⁺ | ¹⁴¹Pm | 1/2+ | | |-id=Samarium-141m | rowspan=2 style="text-indent:1em" | ^141mSm | rowspan=2 colspan="3" style="text-indent:2em" | 175.9(3)&nbsp;keV | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/141Sm-1.pdf 1970] | rowspan=2|22.6(2)&nbsp;min | β⁺ (99.69%) | ¹⁴¹Pm | rowspan=2|11/2− | rowspan=2| | rowspan=2| |- | IT (0.31%) | ¹⁴¹Sm |-id=Samarium-142 | rowspan=2|¹⁴²Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 80 | rowspan=2|141.9152094(20) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/142.pdf 1959] | rowspan=2|72.49(5)&nbsp;min | EC (>95%) | rowspan=2|¹⁴²Pm | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺ (<5%) |-id=Samarium-142m1 | style="text-indent:1em" | ^142m1Sm | colspan="3" style="text-indent:2em" | 2372.1(4)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/142Sm-1.pdf 1975] | 170(2)&nbsp;ns | IT | ¹⁴²Sm | 7− | | |-id=Samarium-142m2 | style="text-indent:1em" | ^142m2Sm | colspan="3" style="text-indent:2em" | 3662.2(7)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/142Sm-2.pdf 1981] | 480(60)&nbsp;ns | IT | ¹⁴²Sm | 10+ | | |-id=Samarium-143 | rowspan=2|¹⁴³Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 81 | rowspan=2|142.9146348(30) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/143.pdf 1956] | rowspan=2|8.75(6)&nbsp;min | EC (60.0%) | ¹⁴³Pm | rowspan=2|3/2+ | rowspan=2| | rowspan=2| |- | β⁺ (40.0%) | ¹⁴³Pm |-id=Samarium-143m1 | rowspan=2 style="text-indent:1em" | ^143m1Sm | rowspan=2 colspan="3" style="text-indent:2em" | 753.99(16)&nbsp;keV | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/143Sm-1.pdf 1960] | rowspan=2|66(2)&nbsp;s | IT (99.76%) | ¹⁴³Sm | rowspan=2|11/2− | rowspan=2| | rowspan=2| |- | β⁺ (0.24%) | ¹⁴³Pm |-id=Samarium-143m2 | style="text-indent:1em" | ^143m2Sm | colspan="3" style="text-indent:2em" | 2793.8(13)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/143Sm-2.pdf 1969] | 30(3)&nbsp;ms | IT | ¹⁴³Sm | 23/2− | | |-id=Samarium-144 | ¹⁴⁴Sm | style="text-align:right" | 62 | style="text-align:right" | 82 | 143.9120063(16) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/144.pdf 1934] | colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS144|r=Believed to undergo β⁺β⁺ decay to '''''¹⁴⁴Nd'''''}} | 0+ | 0.0308(4) | |-id=Samarium-144m | style="text-indent:1em" | ^144mSm | colspan="3" style="text-indent:2em" | 2323.60(8)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/144Sm-1.pdf 1972] | 880(25)&nbsp;ns | IT | '''¹⁴⁴Sm''' | 6+ | | |-id=Samarium-145 | ¹⁴⁵Sm | style="text-align:right" | 62 | style="text-align:right" | 83 | 144.9134172(16) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/145.pdf 1947] | 340(3)&nbsp;d | EC | ¹⁴⁵Pm | 7/2− | | |-id=Samarium-145m | style="text-indent:1em" | ^145mSm | colspan="3" style="text-indent:2em" | 8815(1)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/145Sm-1.pdf 1993] | 3.52(16)&nbsp;μs | IT | ¹⁴⁵Sm | 49/2+ | | |-id=Samarium-146 | ¹⁴⁶Sm | style="text-align:right" | 62 | style="text-align:right" | 84 | 145.9130468(33) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/146.pdf 1953] | 9.20(26){{e|7}}&nbsp;y<ref name=Chiera2024/> | α | '''¹⁴²Nd''' | 0+ | Trace | |-id=Samarium-147 | ¹⁴⁷Sm<ref group="n" name="PN">Primordial radioisotope</ref><ref group="n" name="FP">Fission product</ref><ref group="n">Used in Samarium–neodymium dating</ref> | style="text-align:right" | 62 | style="text-align:right" | 85 | 146.9149044(14) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/147.pdf 1933] | '''1.066(5){{e|11}}&nbsp;y''' | α | '''¹⁴³Nd''' | 7/2− | 0.1500(14) | |-id=Samarium-148 | ¹⁴⁸Sm<ref group="n" name="PN" /> | style="text-align:right" | 62 | style="text-align:right" | 86 | 147.9148292(13) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/148.pdf 1933] | '''6.3(13){{e|15}}&nbsp;y''' | α | '''''¹⁴⁴Nd''''' | 0+ | 0.1125(9) | |-id=Samarium-149 | ¹⁴⁹Sm<ref group="n" name="FP" /><ref group="n" name="NP">Neutron poison in reactors</ref> | style="text-align:right" | 62 | style="text-align:right" | 87 | 148.9171912(12) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/149.pdf 1933] | colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS149|r=Believed to undergo α decay to '''¹⁴⁵Nd''' with a half-life over {{val|2|e=15|u=years}}<ref name="rare_decays">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |title=Experimental searches for rare alpha and beta decays |date=2019 |journal=European Physical Journal A |volume=55 |number=140 |pages=4–6 <!--data table--> |doi=10.1140/epja/i2019-12823-2 | arxiv=1908.11458 |bibcode=2019EPJA...55..140B |s2cid=201664098 }}</ref>}} | 7/2− | 0.1382(10) | |-id=Samarium-150 | ¹⁵⁰Sm | style="text-align:right" | 62 | style="text-align:right" | 88 | 149.9172820(12) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/150.pdf 1934] | colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS150|r=Believed to undergo α decay to '''¹⁴⁶Nd'''<ref name="rare_decays"/>}} | 0+ | 0.0737(9) | |-id=Samarium-151 | ¹⁵¹Sm<ref group="n" name="FP" /><ref group="n" name="NP" /> | style="text-align:right" | 62 | style="text-align:right" | 89 | 150.9199389(12) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/151.pdf 1947] | 94.6(6)&nbsp;y | β⁻ | '''''¹⁵¹Eu''''' | 5/2− | | |-id=Samarium-151m | style="text-indent:1em" | ^151mSm | colspan="3" style="text-indent:2em" | 261.13(4)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/151Sm-1.pdf 1970] | 1.4(1)&nbsp;μs | IT | ¹⁵¹Sm | (11/2)− | | |-id=Samarium-152 | ¹⁵²Sm<ref group="n" name="FP" /> | style="text-align:right" | 62 | style="text-align:right" | 90 | 151.9197386(11) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/152.pdf 1933] | colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS152|r=Believed to undergo α decay to '''¹⁴⁸Nd'''<ref name="rare_decays"/>}} | 0+ | 0.2674(9) | |-id=Samarium-153 | ¹⁵³Sm<ref group="n" name="FP" /> | style="text-align:right" | 62 | style="text-align:right" | 91 | 152.9221036(11) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/153.pdf 1938] | 46.2846(23)&nbsp;h | β⁻ | '''¹⁵³Eu''' | 3/2+ | | |-id=Samarium-153m | style="text-indent:1em" | ^153mSm | colspan="3" style="text-indent:2em" | 98.39(10)&nbsp;keV | style="text-align:center" | (1971)<ref group="n">Only published in a conference proceeding and not a refereed journal.</ref> | 10.6(3)&nbsp;ms | IT | ¹⁵³Sm | 11/2− | | |-id=Samarium-154 | ¹⁵⁴Sm<ref group="n" name="FP" /> | style="text-align:right" | 62 | style="text-align:right" | 92 | 153.9222158(14) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/154.pdf 1933] | colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS154|r=Believed to undergo β⁻β⁻ decay to '''¹⁵⁴Gd''' with a half-life over {{val|2.3|e=18|u=years}}}} | 0+ | 0.2274(14) | |-id=Samarium-155 | ¹⁵⁵Sm | style="text-align:right" | 62 | style="text-align:right" | 93 | 154.9246466(14) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/155.pdf 1951] | 22.18(6)&nbsp;min | β⁻ | ¹⁵⁵Eu | 3/2− | | |-id=Samarium-155m1 | style="text-indent:1em" | ^155m1Sm | colspan="3" style="text-indent:2em" | 16.5467(19)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/155Sm-1.pdf 2010] | 2.8(5)&nbsp;μs | IT | ¹⁵⁵Sm | 5/2+ | | |-id=Samarium-155m2 | style="text-indent:1em" | ^155m2Sm | colspan="3" style="text-indent:2em" | 538.03(19)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/155Sm-2.pdf 2010] | 1.00(8)&nbsp;μs | IT | ¹⁵⁵Sm | 11/2− | | |-id=Samarium-156 | ¹⁵⁶Sm | style="text-align:right" | 62 | style="text-align:right" | 94 | 155.9255382(91) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/156.pdf 1951] | 9.4(2)&nbsp;h | β⁻ | ¹⁵⁶Eu | 0+ | | |-id=Samarium-156m | style="text-indent:1em" | ^156mSm | colspan="3" style="text-indent:2em" | 1397.55(9)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/156Sm-1.pdf 1990] | 185(7)&nbsp;ns | IT | ¹⁵⁶Sm | 5− | | |-id=Samarium-157 | ¹⁵⁷Sm | style="text-align:right" | 62 | style="text-align:right" | 95 | 156.9284186(48) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/157.pdf 1973] | 8.03(7)&nbsp;min | β⁻ | ¹⁵⁷Eu | 3/2−# | | |-id=Samarium-158 | ¹⁵⁸Sm | style="text-align:right" | 62 | style="text-align:right" | 96 | 157.9299493(51) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/158.pdf 1970] | 5.30(3)&nbsp;min | β⁻ | ¹⁵⁸Eu | 0+ | | |-id=Samarium-159 | ¹⁵⁹Sm | style="text-align:right" | 62 | style="text-align:right" | 97 | 158.9332171(64) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/159.pdf 1986] | 11.37(15)&nbsp;s | β⁻ | ¹⁵⁹Eu | 5/2− | | |-id=Samarium-159m | style="text-indent:1em" | ^159mSm | colspan="3" style="text-indent:2em" | 1276.5(8)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/159Sm-1.pdf 2009] | 116(8)&nbsp;ns | IT | ¹⁵⁹Sm | (15/2+) | | |-id=Samarium-160 | ¹⁶⁰Sm | style="text-align:right" | 62 | style="text-align:right" | 98 | 159.9353370(21) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/160.pdf 1986] | 9.6(3)&nbsp;s | β⁻ | ¹⁶⁰Eu | 0+ | | |-id=Samarium-160m1 | style="text-indent:1em" | ^160m1Sm | colspan="3" style="text-indent:2em" | 1361.3(4)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/160Sm-1.pdf 2009] | 120(46)&nbsp;ns | IT | ¹⁶⁰Sm | (5−) | | |-id=Samarium-160m2 | style="text-indent:1em" | ^160m2Sm | colspan="3" style="text-indent:2em" | 2757.3(4)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/160Sm-2.pdf 2016] | 1.8(4)&nbsp;μs | IT | ¹⁶⁰Sm | (11+) | | |-id=Samarium-161 | ¹⁶¹Sm | style="text-align:right" | 62 | style="text-align:right" | 99 | 160.9391601(73) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/161.pdf 1998] | 4.8(4)&nbsp;s | β⁻ | ¹⁶¹Eu | 7/2+# | | |-id=Samarium-161m | style="text-indent:1em" | ^161mSm | colspan="3" style="text-indent:2em" | 1388.1(6)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/161Sm-1.pdf 2017] | 2.6(4)&nbsp;μs | IT | ¹⁶¹Sm | (17/2−) | | |-id=Samarium-162 | ¹⁶²Sm | style="text-align:right" | 62 | style="text-align:right" | 100 | 161.9416217(38) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/162.pdf 2005] | 2.7(3)&nbsp;s | β⁻ | ¹⁶²Eu | 0+ | | |-id=Samarium-162m | style="text-indent:1em" | ^162mSm | colspan="3" style="text-indent:2em" | 1009.4(5)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/162Sm-1.pdf 2017] | 1.78(7)&nbsp;μs | IT | ¹⁶²Sm | (4−) | | |-id=Samarium-163 | rowspan=2|¹⁶³Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 101 | rowspan=2|162.9456791(79) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/163.pdf 2012] | rowspan=2|{{val|1.744|0.180|0.204|u=s}}<ref name=Ln922>{{cite journal |last1=Kiss |first1=G. G. |last2=Vitéz-Sveiczer |first2=A. |last3=Saito |first3=Y. |display-authors=et al. |title=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 |journal=The Astrophysical Journal |volume=936 |issue=107 |date=2022 |page=107 |doi=10.3847/1538-4357/ac80fc|bibcode=2022ApJ...936..107K |doi-access=free |hdl=2117/375253 |hdl-access=free }}</ref><!--only half-lives updated on 2022-11-25--> | β⁻ | ¹⁶³Eu | rowspan=2|1/2−# | rowspan=2| | rowspan=2| |- | β⁻, n (<0.1%) | ¹⁶²Eu |-id=Samarium-164 | rowspan=2|¹⁶⁴Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 102 | rowspan=2|163.9485501(44) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/164.pdf 2012] | rowspan=2|{{val|1.422|0.54|0.59|u=s}}<ref name=Ln922/> | β⁻ | ¹⁶⁴Eu | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁻, n (<0.7%) | ¹⁶³Eu |-id=Samarium-164m | style="text-indent:1em" | ^164mSm | colspan="3" style="text-indent:2em" | 1485.5(12)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/62/164Sm-1.pdf 2014] | 600(140)&nbsp;ns | IT | ¹⁶⁴Sm | (6−) | | |-id=Samarium-165 | rowspan=2|¹⁶⁵Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 103 | rowspan=2|164.95329(43)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/165.pdf 2012] | rowspan=2|{{val|592|51|55|u=ms}}<ref name=Ln922/> | β⁻ (98.64%) | ¹⁶⁵Eu | rowspan=2|5/2−# | rowspan=2| | rowspan=2| |- | β⁻, n (1.36%) | ¹⁶⁴Eu |-id=Samarium-166 | rowspan=2|¹⁶⁶Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 104 | rowspan=2|165.95658(43)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/166.pdf 2017] | rowspan=2|{{val|396|56|63|u=ms}}<ref name=Ln922/> | β⁻ (95.62%) | ¹⁶⁶Eu | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁻, n (4.38%) | ¹⁶⁵Eu |-id=Samarium-167 | rowspan=2|¹⁶⁷Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 105 | rowspan=2|166.96207(54)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/167.pdf 2018] | rowspan=2|{{val|334|83|78|u=ms}}<ref name=Ln922/> | β⁻ | ¹⁶⁷Eu | rowspan=2|7/2−# | rowspan=2| | rowspan=2| |- | β⁻, n (<16%) | ¹⁶⁶Eu |-id=Samarium-168 | rowspan=2|¹⁶⁸Sm | rowspan=2 style="text-align:right" | 62 | rowspan=2 style="text-align:right" | 106 | rowspan=2|167.96603(32)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/62/168.pdf 2022] | rowspan=2|{{val|353|210|164|u=ms}}<ref name=Ln922/> | β⁻ | ¹⁶⁸Eu | rowspan=2|0+# | rowspan=2| | rowspan=2| |- | β⁻, n (<21%) | ¹⁶⁷Eu {{Isotopes table/footer}}

==Samarium-149== Samarium-149 (¹⁴⁹Sm) is an observationally stable isotope of samarium (predicted to decay, but no decays have ever been observed, giving it a half-life at least several orders of magnitude longer than the age of the universe), and a product of the decay chain from the fission product ¹⁴⁹Nd (yield 1.0888%). ¹⁴⁹Sm is a neutron-absorbing nuclear poison with significant effect on nuclear reactor operation, second only to ¹³⁵Xe. Its neutron cross section is 40140 barns for thermal neutrons.

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 xenon-135, which accumulates from the beta decay of iodine-135 (a short lived fission product) and has a high neutron cross section, but itself decays with a half-life of 9.2 hours (so does not remain in constant concentration long after the reactor shutdown), causing the so-called xenon pit.

==Samarium-151==

{{Medium-lived fission products}}

{{Chain yield| 0.399 ± 0.065| 0.165 ± 0.035 | 0.333 ± 0.017| 0.312 ± 0.014| 0.49 ± 0.11 | 0.4204 ± 0.0071|0.431 ± 0.015|0.388 ± 0.061 | 0.810 ± 0.012| 0.800 ± 0.057 | 0.776 ± 0.018| 0.797 ± 0.037 | ? | 0.86 ± 0.24| 0.910 ± 0.025 | ? | data_ref=<ref>https://www-nds.iaea.org/sgnucdat/c3.htm Cumulative Fission Yields, IAEA</ref>}}

Samarium-151 (¹⁵¹Sm) has a half-life of 94.6 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 neutron absorption cross section for thermal neutrons is high at 15200 barns, about 38% of ¹⁴⁹Sm's absorption cross section, or about 20 times that of ²³⁵U. Since the ratios between the production and absorption rates of ¹⁵¹Sm and ¹⁴⁹Sm are almost equal, the two isotopes should reach similar equilibrium concentrations. Since ¹⁴⁹Sm reaches equilibrium in about 500 hours (20 days), ¹⁵¹Sm should reach equilibrium in about 50 days. As this is still much shorter than its radioactive half-life, decay will hardly affect this equilibrium while in the reactor.

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 MOX fuel and about half that for uranium fuel, which is roughly two orders of magnitude less than the mass fraction of about 0.15 for the medium-lived fission product ¹³⁷Cs.<ref>{{cite report |author=Christophe Demazière |title=Reactor Physics Calculations on MOX Fuel in Boiling Water Reactors (BWRs) |url=http://www.oecd-nea.org/pt/docs/iem/jeju02/session5/SectionV-12.pdf |publisher=OECD Nuclear Energy Agency}} Figure 2, page 6</ref> The decay energy of ¹⁵¹Sm is also about an order of magnitude less than that of ¹³⁷Cs. The low yield, low survival rate, and low decay energy mean that ¹⁵¹Sm has insignificant nuclear waste impact compared to the two main medium-lived fission products ¹³⁷Cs and ⁹⁰Sr. *[https://web.archive.org/web/20120407032958/http://www.ead.anl.gov/pub/doc/samarium.pdf ANL factsheet]

==Samarium-153== Samarium-153 (¹⁵³Sm) has a half-life of 46.285 hours, undergoing β⁻ decay into stable ¹⁵³Eu. As a component of samarium lexidronam, it is used in palliation of bone cancer.<ref name="BallantyneFishman2009">{{cite book|last1=Ballantyne|first1=Jane C|last2=Fishman|first2=Scott M|last3=Rathmell|first3=James P.|title=Bonica's Management of Pain|url=https://books.google.com/books?id=Pms0hxH8f-sC&pg=PA655|access-date=19 July 2011|date=2009-10-01|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-6827-6|pages=655–}}</ref> It is treated by the body in a similar manner to calcium, and it localizes selectively to bone.

== See also == '''Daughter products other than samarium''' * Isotopes of europium * Isotopes of promethium * Isotopes of neodymium

== References == {{reflist}}

{{Navbox element isotopes}}

Category:Isotopes of samarium Category:Samarium Samarium