View source for Isotopes of samarium

{{Short description|none}}
{{Infobox samarium isotopes}}
Naturally occurring [[samarium]] (<sub>62</sub>Sm) is composed of five stable [[isotope]]s, <sup>144</sup>Sm, <sup>149</sup>Sm, <sup>150</sup>Sm, <sup>152</sup>Sm and <sup>154</sup>Sm, and two extremely long-lived [[radioisotope]]s, <sup>147</sup>Sm (half life: 1.066{{e|11}}&nbsp;y) and <sup>148</sup>Sm (6.3{{e|15}}&nbsp;y), with <sup>152</sup>Sm being the most abundant (26.75% [[natural abundance]]). <sup>146</sup>Sm (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 nuclide|primordial]]. Its instability is due to having 84 neutrons (two more than 82, which is a [[magic number (physics)|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 the naturally occurring isotopes, the longest-lived radioisotopes are <sup>151</sup>Sm, 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 <sup>151</sup>Sm remeasured | journal = Physical Review C | volume = 80 | issue = 6 | year = 2009 | page = 064305 |bibcode = 2009PhRvC..80f4305H }}</ref> and <sup>145</sup>Sm, which has a half-life of 340 days. All of the remaining radioisotopes, which range from <sup>129</sup>Sm to <sup>168</sup>Sm, 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 [[nuclear isomer|isomers]] with the most stable being <sup>141m</sup>Sm (t<sub>1/2</sub> 22.6 minutes), <sup>143m1</sup>Sm (t<sub>1/2</sub> 66 seconds) and <sup>139m</sup>Sm (t<sub>1/2</sub> 10.7 seconds).

The long lived isotopes, <sup>146</sup>Sm, <sup>147</sup>Sm, and <sup>148</sup>Sm, 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]]. 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 <sup>146</sup>Sm  from 10.3(5)×10<sup>7</sup>&nbsp;y to 6.8(7)×10<sup>7</sup>&nbsp;y was retracted 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>

Isotopes of samarium are used in [[samarium–neodymium dating]] for determining the age relationships of rocks and meteorites.

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

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 ==
{{Anchor|Samarium-128|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 -->
| notes = m, unc(), mass#, exen#, hl#, hl-nst, spin(), spin#, p, IT, daughter-st, daughter-nst
}}
|-id=Samarium-129
| rowspan=2|<sup>129</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 67
| rowspan=2|128.95456(54)#
| rowspan=2|550(100)&nbsp;ms
| [[beta decay|β<sup>+</sup>]] (?%)
| <sup>129</sup>Pm
| rowspan=2|(1/2+,3/2+)
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup>, p (?%)
| <sup>128</sup>Nd
|-id=Samarium-130
| <sup>130</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 68
| 129.94879(43)#
| 1#&nbsp;s
| 
| 
| 0+
|
|
|-id=Samarium-131
| rowspan=2|<sup>131</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 69
| rowspan=2|130.94602(43)#
| rowspan=2|1.2(2)&nbsp;s
| β<sup>+</sup>
| <sup>131</sup>Pm
| rowspan=2|5/2+#
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup>, p (?%)
| <sup>130</sup>Nd
|-id=Samarium-132
| <sup>132</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 70
| 131.94081(32)#
| 4.0(3)&nbsp;s
| β<sup>+</sup>
| <sup>132</sup>Pm
| 0+
| 
| 
|-id=Samarium-133
| rowspan=2|<sup>133</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 71
| rowspan=2|132.93856(32)#
| rowspan=2|2.89(16)&nbsp;s
| β<sup>+</sup> (?%)
| <sup>133</sup>Pm
| rowspan=2|(5/2+)
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup>, p (?%)
| <sup>132</sup>Nd
|-id=Samarium-133m
| style="text-indent:1em" | <sup>133m</sup>Sm
| colspan="3" style="text-indent:2em" | 120(60)#&nbsp;keV
| 3.5(4)&nbsp;s
| β<sup>+</sup>
| <sup>133</sup>Pm
| (1/2−)
|
|
|-id=Samarium-134
| <sup>134</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 72
| 133.93411(21)#
| 9.5(8)&nbsp;s
| β<sup>+</sup>
| <sup>134</sup>Pm
| 0+
|
|
|-id=Samarium-135
| rowspan=2|<sup>135</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 73
| rowspan=2|134.93252(17)
| rowspan=2|10.3(5)&nbsp;s
| β<sup>+</sup> (99.98%)
| <sup>135</sup>Pm
| rowspan=2|(7/2+)
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup>, p (0.02%)
| <sup>134</sup>Nd
|-id=Samarium-136
| <sup>136</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 74
| 135.928276(13)
| 47(2)&nbsp;s
| β<sup>+</sup>
| <sup>136</sup>Pm
| 0+
|
|
|-id=Samarium-136m
| style="text-indent:1em" | <sup>136m</sup>Sm
| colspan="3" style="text-indent:2em" | 2264.7(11)&nbsp;keV
| 15(1)&nbsp;μs
| IT
| <sup>136</sup>Sm
| (8−)
|
|
|-id=Samarium-137
| <sup>137</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 75
| 136.927008(31)
| 45(1)&nbsp;s
| β<sup>+</sup>
| <sup>137</sup>Pm
| (9/2−)
|
|
|-id=Samarium-138
| <sup>138</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 76
| 137.923244(13)
| 3.1(2)&nbsp;min
| β<sup>+</sup>
| <sup>138</sup>Pm
| 0+
|
|
|-id=Samarium-139
| <sup>139</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 77
| 138.922297(12)
| 2.57(10)&nbsp;min
| β<sup>+</sup>
| <sup>139</sup>Pm
| 1/2+
| 
| 
|-id=Samarium-139m
| rowspan=2 style="text-indent:1em" | <sup>139m</sup>Sm
| rowspan=2 colspan="3" style="text-indent:2em" | 457.38(23)&nbsp;keV
| rowspan=2|10.7(6)&nbsp;s
| [[Isomeric transition|IT]] (93.7%)
| <sup>139</sup>Sm
| rowspan=2|11/2−
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup> (6.3%)
| <sup>139</sup>Pm
|-id=Samarium-140
| <sup>140</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 78
| 139.918995(13)
| 14.82(12)&nbsp;min
| β<sup>+</sup>
| <sup>140</sup>Pm
| 0+
|
|
|-id=Samarium-141
| <sup>141</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 79
| 140.9184815(92)
| 10.2(2)&nbsp;min
| β<sup>+</sup>
| <sup>141</sup>Pm
| 1/2+
|
|
|-id=Samarium-141m
| rowspan=2 style="text-indent:1em" | <sup>141m</sup>Sm
| rowspan=2 colspan="3" style="text-indent:2em" | 175.9(3)&nbsp;keV
| rowspan=2|22.6(2)&nbsp;min
| β<sup>+</sup> (99.69%)
| <sup>141</sup>Pm
| rowspan=2|11/2−
| rowspan=2|
| rowspan=2|
|-
| IT (0.31%)
| <sup>141</sup>Sm
|-id=Samarium-142
| rowspan=2|<sup>142</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 80
| rowspan=2|141.9152094(20)
| rowspan=2|72.49(5)&nbsp;min
| EC (>95%)
| rowspan=2|<sup>142</sup>Pm
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup> (<5%)
|-id=Samarium-142m1
| style="text-indent:1em" | <sup>142m1</sup>Sm
| colspan="3" style="text-indent:2em" | 2372.1(4)&nbsp;keV
| 170(2)&nbsp;ns
| IT
| <sup>142</sup>Sm
| 7−
|
|
|-id=Samarium-142m2
| style="text-indent:1em" | <sup>142m2</sup>Sm
| colspan="3" style="text-indent:2em" | 3662.2(7)&nbsp;keV
| 480(60)&nbsp;ns
| IT
| <sup>142</sup>Sm
| 10+
|
|
|-id=Samarium-143
| rowspan=2|<sup>143</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 81
| rowspan=2|142.9146348(30)
| rowspan=2|8.75(6)&nbsp;min
| EC (60.0%)
| <sup>143</sup>Pm
| rowspan=2|3/2+
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup> (40.0%)
| <sup>143</sup>Pm
|-id=Samarium-143m1
| rowspan=2 style="text-indent:1em" | <sup>143m1</sup>Sm
| rowspan=2 colspan="3" style="text-indent:2em" | 753.99(16)&nbsp;keV
| rowspan=2|66(2)&nbsp;s
| IT (99.76%)
| <sup>143</sup>Sm
| rowspan=2|11/2−
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup> (0.24%)
| <sup>143</sup>Pm
|-id=Samarium-143m2
| style="text-indent:1em" | <sup>143m2</sup>Sm
| colspan="3" style="text-indent:2em" | 2793.8(13)&nbsp;keV
| 30(3)&nbsp;ms
| IT
| <sup>143</sup>Sm
| 23/2−
|
|
|-id=Samarium-144
| <sup>144</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 82
| 143.9120063(16)
| colspan=3 align=center|'''[[Observationally stable]]'''{{r|g=n|OS144|r=Believed to undergo β<sup>+</sup>β<sup>+</sup> decay to '''''<sup>144</sup>Nd'''''}}
| 0+
| 0.0308(4)
|
|-id=Samarium-144m
| style="text-indent:1em" | <sup>144m</sup>Sm
| colspan="3" style="text-indent:2em" | 2323.60(8)&nbsp;keV
| 880(25)&nbsp;ns
| IT
| '''<sup>144</sup>Sm'''
| 6+
|
|
|-id=Samarium-145
| <sup>145</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 83
| 144.9134172(16)
| 340(3)&nbsp;d
| [[Electron capture|EC]]
| <sup>145</sup>Pm
| 7/2−
|
|
|-id=Samarium-145m
| style="text-indent:1em" | <sup>145m</sup>Sm
| colspan="3" style="text-indent:2em" | 8815(1)&nbsp;keV
| 3.52(16)&nbsp;μs
| IT
| <sup>145</sup>Sm
| 49/2+
|
|
|-id=Samarium-146
| <sup>146</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 84
| 145.9130468(33)
| 9.20(26){{e|7}}&nbsp;y<ref name=Chiera2024/>
| [[alpha decay|α]]
| '''<sup>142</sup>Nd'''
| 0+
| Trace
|
|-
| [[Samarium-147|<sup>147</sup>Sm]]<ref group="n" name="PN">[[Primordial nuclide|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)
| '''1.066(5){{e|11}}&nbsp;y'''
| α
| '''<sup>143</sup>Nd'''
| 7/2−
| 0.1500(14)
|
|-id=Samarium-148
| <sup>148</sup>Sm<ref group="n" name="PN" />
| style="text-align:right" | 62
| style="text-align:right" | 86
| 147.9148292(13)
| '''6.3(13){{e|15}}&nbsp;y'''
| α
| '''''<sup>144</sup>Nd'''''
| 0+
| 0.1125(9)
|
|-
| <sup>149</sup>Sm<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)
| colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS149|r=Believed to undergo α decay to '''<sup>145</sup>Nd''' 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
| <sup>150</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 88
| 149.9172820(12)
| colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS150|r=Believed to undergo α decay to '''<sup>146</sup>Nd'''<ref name="rare_decays"/>}}
| 0+
| 0.0737(9)
|
|-
| <sup>151</sup>Sm<ref group="n" name="FP" /><ref group="n" name="NP" />
| style="text-align:right" | 62
| style="text-align:right" | 89
| 150.9199389(12)
| 94.6(6)&nbsp;y
| β<sup>−</sup>
| '''''<sup>151</sup>Eu'''''
| 5/2−
|
|
|-id=Samarium-151m
| style="text-indent:1em" | <sup>151m</sup>Sm
| colspan="3" style="text-indent:2em" | 261.13(4)&nbsp;keV
| 1.4(1)&nbsp;μs
| IT
| <sup>151</sup>Sm
| (11/2)−
|
|
|-id=Samarium-152
| <sup>152</sup>Sm<ref group="n" name="FP" />
| style="text-align:right" | 62
| style="text-align:right" | 90
| 151.9197386(11)
| colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS152|r=Believed to undergo α decay to '''<sup>148</sup>Nd'''<ref name="rare_decays"/>}}
| 0+
| 0.2674(9)
|
|-
| <sup>153</sup>Sm<ref group="n" name="FP" />
| style="text-align:right" | 62
| style="text-align:right" | 91
| 152.9221036(11)
| 46.2846(23)&nbsp;h
| β<sup>−</sup>
| '''<sup>153</sup>Eu'''
| 3/2+
|
|
|-id=Samarium-153m
| style="text-indent:1em" | <sup>153m</sup>Sm
| colspan="3" style="text-indent:2em" | 98.39(10)&nbsp;keV
| 10.6(3)&nbsp;ms
| IT
| <sup>153</sup>Sm
| 11/2−
|
|
|-id=Samarium-154
| <sup>154</sup>Sm<ref group="n" name="FP" />
| style="text-align:right" | 62
| style="text-align:right" | 92
| 153.9222158(14)
| colspan=3 align=center|'''Observationally stable'''{{r|g=n|OS154|r=Believed to undergo β<sup>−</sup>β<sup>−</sup> decay to '''<sup>154</sup>Gd''' with a [[half-life]] over {{val|2.3|e=18|u=years}}}}
| 0+
| 0.2274(14)
|
|-id=Samarium-155
| <sup>155</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 93
| 154.9246466(14)
| 22.18(6)&nbsp;min
| β<sup>−</sup>
| <sup>155</sup>Eu
| 3/2−
|
|
|-id=Samarium-155m1
| style="text-indent:1em" | <sup>155m1</sup>Sm
| colspan="3" style="text-indent:2em" | 16.5467(19)&nbsp;keV
| 2.8(5)&nbsp;μs
| IT
| <sup>155</sup>Sm
| 5/2+
|
|
|-id=Samarium-155m2
| style="text-indent:1em" | <sup>155m2</sup>Sm
| colspan="3" style="text-indent:2em" | 538.03(19)&nbsp;keV
| 1.00(8)&nbsp;μs
| IT
| <sup>155</sup>Sm
| 11/2−
|
|
|-id=Samarium-156
| <sup>156</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 94
| 155.9255382(91)
| 9.4(2)&nbsp;h
| β<sup>−</sup>
| <sup>156</sup>Eu
| 0+
|
|
|-id=Samarium-156m
| style="text-indent:1em" | <sup>156m</sup>Sm
| colspan="3" style="text-indent:2em" | 1397.55(9)&nbsp;keV
| 185(7)&nbsp;ns
| IT
| <sup>156</sup>Sm
| 5−
|
|
|-id=Samarium-157
| <sup>157</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 95
| 156.9284186(48)
| 8.03(7)&nbsp;min
| β<sup>−</sup>
| <sup>157</sup>Eu
| 3/2−#
|
|
|-id=Samarium-158
| <sup>158</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 96
| 157.9299493(51)
| 5.30(3)&nbsp;min
| β<sup>−</sup>
| <sup>158</sup>Eu
| 0+
|
|
|-id=Samarium-159
| <sup>159</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 97
| 158.9332171(64)
| 11.37(15)&nbsp;s
| β<sup>−</sup>
| <sup>159</sup>Eu
| 5/2−
|
|
|-id=Samarium-159m
| style="text-indent:1em" | <sup>159m</sup>Sm
| colspan="3" style="text-indent:2em" | 1276.5(8)&nbsp;keV
| 116(8)&nbsp;ns
| IT
| <sup>159</sup>Sm
| (15/2+)
| 
|
|-id=Samarium-160
| <sup>160</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 98
| 159.9353370(21)
| 9.6(3)&nbsp;s
| β<sup>−</sup>
| <sup>160</sup>Eu
| 0+
|
|
|-id=Samarium-160m1
| style="text-indent:1em" | <sup>160m1</sup>Sm
| colspan="3" style="text-indent:2em" | 1361.3(4)&nbsp;keV
| 120(46)&nbsp;ns
| IT
| <sup>160</sup>Sm
| (5−)
| 
|
|-id=Samarium-160m2
| style="text-indent:1em" | <sup>160m2</sup>Sm
| colspan="3" style="text-indent:2em" | 2757.3(4)&nbsp;keV
| 1.8(4)&nbsp;μs
| IT
| <sup>160</sup>Sm
| (11+)
| 
|
|-id=Samarium-161
| <sup>161</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 99
| 160.9391601(73)
| {{val|4.349|0.425|0.441|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<sup>−</sup>
| <sup>161</sup>Eu
| 7/2+#
|
|
|-id=Samarium-161m
| style="text-indent:1em" | <sup>161m</sup>Sm
| colspan="3" style="text-indent:2em" | 1388.1(6)&nbsp;keV
| 2.6(4)&nbsp;μs
| IT
| <sup>161</sup>Sm
| (17/2−)
| 
|
|-id=Samarium-162
| <sup>162</sup>Sm
| style="text-align:right" | 62
| style="text-align:right" | 100
| 161.9416217(38)
| {{val|3.369|0.200|0.303|u=s}}<ref name=Ln922/>
| β<sup>−</sup>
| <sup>162</sup>Eu
| 0+
|
|
|-id=Samarium-162m
| style="text-indent:1em" | <sup>162m</sup>Sm
| colspan="3" style="text-indent:2em" | 1009.4(5)&nbsp;keV
| 1.78(7)&nbsp;μs
| IT
| <sup>162</sup>Sm
| (4−)
| 
|
|-id=Samarium-163
| rowspan=2|<sup>163</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 101
| rowspan=2|162.9456791(79)
| rowspan=2|{{val|1.744|0.180|0.204|u=s}}<ref name=Ln922/>
| β<sup>−</sup>
| <sup>163</sup>Eu
| rowspan=2|1/2−#
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n (<0.1%)
| <sup>162</sup>Eu
|-id=Samarium-164
| rowspan=2|<sup>164</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 102
| rowspan=2|163.9485501(44)
| rowspan=2|{{val|1.422|0.54|0.59|u=s}}<ref name=Ln922/>
| β<sup>−</sup>
| <sup>164</sup>Eu
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n (<0.7%)
| <sup>163</sup>Eu
|-id=Samarium-164m
| style="text-indent:1em" | <sup>164m</sup>Sm
| colspan="3" style="text-indent:2em" | 1485.5(12)&nbsp;keV
| 600(140)&nbsp;ns
| IT
| <sup>164</sup>Sm
| (6−)
| 
|
|-id=Samarium-165
| rowspan=2|<sup>165</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 103
| rowspan=2|164.95329(43)#
| rowspan=2|{{val|592|51|55|u=ms}}<ref name=Ln922/>
| β<sup>−</sup> (98.64%)
| <sup>165</sup>Eu
| rowspan=2|5/2−#
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n (1.36%)
| <sup>164</sup>Eu
|-id=Samarium-166
| rowspan=2|<sup>166</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 104
| rowspan=2|165.95658(43)#
| rowspan=2|{{val|396|56|63|u=ms}}<ref name=Ln922/>
| β<sup>−</sup> (95.62%)
| <sup>166</sup>Eu
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n (4.38%)
| <sup>165</sup>Eu
|-id=Samarium-167
| rowspan=2|<sup>167</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 105
| rowspan=2|166.96207(54)#
| rowspan=2|{{val|334|83|78|u=ms}}<ref name=Ln922/>
| β<sup>−</sup>
| <sup>167</sup>Eu
| rowspan=2|7/2−#
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n (<16%)
| <sup>166</sup>Eu
|-id=Samarium-168
| rowspan=2|<sup>168</sup>Sm
| rowspan=2 style="text-align:right" | 62
| rowspan=2 style="text-align:right" | 106
| rowspan=2|167.96603(32)#
| rowspan=2|{{val|353|210|164|u=ms}}<ref name=Ln922/>
| β<sup>−</sup>
| <sup>168</sup>Eu
| rowspan=2|0+#
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n (<21%)
| <sup>167</sup>Eu
{{Isotopes table/footer}}

==Samarium-149==
Samarium-149 (<sup>149</sup>Sm) 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]] <sup>149</sup>Nd (yield 1.0888%). <sup>149</sup>Sm is a [[neutron]]-absorbing [[nuclear poison]] with significant effect on [[nuclear reactor]] operation, second only to [[Xenon-135|<sup>135</sup>Xe]]. Its [[neutron cross section]] is 40140 [[Barn (unit)|barn]]s for [[thermal neutron]]s.

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 <sup>149</sup>Sm 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 (<sup>151</sup>Sm) 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 [[Uranium-235|<sup>235</sup>U]], about 39% of <sup>149</sup>Sm's yield. The yield is somewhat higher for [[Plutonium-239|<sup>239</sup>Pu]].

Its [[neutron absorption]] [[Neutron cross-section|cross section]] for [[thermal neutron]]s is high at 15200 [[barn (unit)|barn]]s, about 38% of <sup>149</sup>Sm's absorption cross section, or about 20 times that of <sup>235</sup>U. Since the ratios between the production and absorption rates of <sup>151</sup>Sm and <sup>149</sup>Sm are almost equal, the two isotopes should reach similar equilibrium concentrations. Since <sup>149</sup>Sm reaches equilibrium in about 500 hours (20 days), <sup>151</sup>Sm should reach equilibrium in about 50 days.

Since nuclear fuel is used for several years ([[burnup]]) in a [[nuclear power plant]], the final amount of <sup>151</sup>Sm in the [[spent nuclear fuel]] at discharge is only a small fraction of the total <sup>151</sup>Sm produced during the use of the fuel. 
According to one study, the mass fraction of <sup>151</sup>Sm 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]] [[Caesium-137|<sup>137</sup>Cs]].<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 <sup>151</sup>Sm is also about an order of magnitude less than that of <sup>137</sup>Cs. The low yield, low survival rate, and low [[decay energy]] mean that <sup>151</sup>Sm has insignificant [[nuclear waste]] impact compared to the two main [[medium-lived fission product]]s <sup>137</sup>Cs and [[Strontium-90|<sup>90</sup>Sr]].
*[https://web.archive.org/web/20120407032958/http://www.ead.anl.gov/pub/doc/samarium.pdf ANL factsheet]

==Samarium-153==
Samarium-153 (<sup>153</sup>Sm) has a half-life of 46.3 hours, undergoing β<sup>−</sup> decay into <sup>153</sup>Eu. As a component of [[Samarium (153Sm) lexidronam|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]]
[[Category:Lists of isotopes by element|Samarium]]