Isotopes of promethium
Template:Short description Template:Infobox promethium isotopes Promethium (61Pm) is an artificial element, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was first synthesized in 1945. Like technetium, it is preceded and followed by elements with stable isotopes.
The known isotopes run from 128Pm to 166Pm, 39 in all; the most stable are 145Pm with a half-life of 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm (the common isotope) with a half-life of 2.6234 years. 143Pm and 144Pm also have lengthy if poorly-known lives on the order of a year, but all the others have half-lives that are less than six days, with the majority less than a few minutes. There are also 24 known meta states with the most stable being 148mPm at a half-life of 41.29 days.
The primary decay mode for isotopes lighter than 146Pm is electron capture resulting in isotopes of neodymium, and the primary decay mode heavier than 146Pm is beta decay giving isotopes of samarium; promethium-146 itself decays both ways.
List of isotopes
Template:Isotopes table
|-id=Promethium-125
| 125Pm[1]
| style="text-align:right" | 61
| style="text-align:right" | 64
|
| style="text-align:center" | 2025
| >310 ns
|
|
|
|
|-id=Promethium-126
| 126Pm[1]
| style="text-align:right" | 61
| style="text-align:right" | 65
| 125.95733(54)#
| style="text-align:center" | 2025
| 500# ms
[>310 ns]
|
|
|
|
|-id=Promethium-127
| 127Pm[1]
| style="text-align:right" | 61
| style="text-align:right" | 66
| 126.95136(43)#
| style="text-align:center" | 2025
| 1# s
[>310 ns]
|
|
| 3/2+#
|
|-id=Promethium-128
| rowspan=2|128Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 67
| rowspan=2|127.94823(32)#
| rowspan=2 style="text-align:center" | 1999
| rowspan=2|1.0(3) s
| β+ (?%)
| 128Nd
| rowspan=2|4+#
| rowspan=2|
|-
| β+, p (?%)
| 127Pr
|-id=Promethium-129
| 129Pm
| style="text-align:right" | 61
| style="text-align:right" | 68
| 128.94291(32)#
| style="text-align:center" | 2004
| 2.4(9) s
| β+
| 129Nd
| 5/2+#
|
|-id=Promethium-130
| rowspan=2|130Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 69
| rowspan=2|129.94045(22)#
| rowspan=2 style="text-align:center" | 1985
| rowspan=2|2.6(2) s
| β+ (?%)
| 130Nd
| rowspan=2|(5+, 6+, 4+)
| rowspan=2|
|-
| β+, p (?%)
| 129Pr
|-id=Promethium-131
| 131Pm
| style="text-align:right" | 61
| style="text-align:right" | 70
| 130.93583(22)#
| style="text-align:center" | 1998
| 6.3(8) s
| β+
| 131Nd
| (11/2−)
|
|-id=Promethium-132
| rowspan=2|132Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 71
| rowspan=2|131.93384(16)#
| rowspan=2 style="text-align:center" | 1977
| rowspan=2|6.2(6) s
| β+
| 132Nd
| rowspan=2|(3+)
| rowspan=2|
|-
| β+, p (5×10−5%)
| 131Pr
|-id=Promethium-133
| 133Pm
| style="text-align:right" | 61
| style="text-align:right" | 72
| 132.929782(54)
| style="text-align:center" | 1977
| 13.5(21) s
| β+
| 133Nd
| (3/2+)
|
|-id=Promethium-133m
| style="text-indent:1em" | 133mPm
| colspan="3" style="text-indent:2em" | 129.7(7) keV
| style="text-align:center" | (1996)[n 1]
| 8# s
|
|
| (11/2−)
|
|-id=Promethium-134
| 134Pm
| style="text-align:right" | 61
| style="text-align:right" | 73
| 133.928326(45)
| style="text-align:center" | 1977
| 22(1) s
| β+
| 134Nd
| (5+)
|
|-id=Promethium-134m1
| style="text-indent:1em" | 134m1Pm
| colspan="3" style="text-indent:2em" | 50(50)# keV[n 2]
| style="text-align:center" | 1989
| ~5 s
| β+
| 134Nd
| (2+)
|
|-id=Promethium-134m2
| style="text-indent:1em" | 134m2Pm
| colspan="3" style="text-indent:2em" | 120(50)# keV
| style="text-align:center" | 2009
| 20(1) μs
| IT
| 134Pm
| (7−)
|
|-id=Promethium-135
| 135Pm
| style="text-align:right" | 61
| style="text-align:right" | 74
| 134.924785(89)
| style="text-align:center" | 1975
| 49(3) s
| β+
| 135Nd
| (3/2+, 5/2+)
|
|-id=Promethium-135m
| style="text-indent:1em" | 135mPm
| colspan="3" style="text-indent:2em" | 240(100)# keV
| style="text-align:center" | 1989
| 40(3) s
| β+
| 135Nd
| (11/2−)
|
|-id=Promethium-136
| 136Pm
| style="text-align:right" | 61
| style="text-align:right" | 75
| 135.923596(74)
| style="text-align:center" | 1982
| 107(6) s
| β+
| 136Nd
| 7+#
|
|-id=Promethium-136m1
| style="text-indent:1em" | 136m1Pm[n 2]
| colspan="3" style="text-indent:2em" | 100(120) keV
| style="text-align:center" | 1988
| 90(35) s
| β+
| 136Nd
| 2+#
|
|-id=Promethium-136m2
| style="text-indent:1em" | 136m2Pm
| colspan="3" style="text-indent:2em" | 42.7(2) keV
| style="text-align:center" | 2008
| 1.5(1) μs
| IT
| 136Pm
| 7−#
|
|-id=Promethium-137
| 137Pm
| style="text-align:right" | 61
| style="text-align:right" | 76
| 136.920480(14)
| style="text-align:center" | 1975
| 2# min
|
|
| 5/2−#
|
|-id=Promethium-137m
| style="text-indent:1em" | 137mPm
| colspan="3" style="text-indent:2em" | 160(50) keV
| style="text-align:center" | (1973)[n 3]
| 2.4(1) min
| β+
| 137Nd
| 11/2−
|
|-id=Promethium-138
| 138Pm
| style="text-align:right" | 61
| style="text-align:right" | 77
| 137.919576(12)
| style="text-align:center" | 1981
| 3.24(5) min
| β+
| 138Nd
| 3−#
|
|-id=Promethium-139
| 139Pm
| style="text-align:right" | 61
| style="text-align:right" | 78
| 138.916799(15)
| style="text-align:center" | 1967
| 4.15(5) min
| β+
| 139Nd
| (5/2)+
|
|-id=Promethium-139m
| style="text-indent:1em" | 139mPm
| colspan="3" style="text-indent:2em" | 188.7(3) keV
| style="text-align:center" | 1975
| 180(20) ms
| IT
| 139Pm
| (11/2)−
|
|-id=Promethium-140
| 140Pm
| style="text-align:right" | 61
| style="text-align:right" | 79
| 139.916036(26)
| style="text-align:center" | 1966
| 9.2(2) s
| β+
| 140Nd
| 1+
|
|-id=Promethium-140m
| style="text-indent:1em" | 140mPm
| colspan="3" style="text-indent:2em" | 429(28) keV
| style="text-align:center" | 1968
| 5.95(5) min
| β+
| 140Nd
| 8−
|
|-id=Promethium-141
| 141Pm
| style="text-align:right" | 61
| style="text-align:right" | 80
| 140.913555(15)
| style="text-align:center" | 1952
| 20.90(5) min
| β+
| 141Nd
| 5/2+
|
|-id=Promethium-141m1
| style="text-indent:1em" | 141m1Pm
| colspan="3" style="text-indent:2em" | 628.62(7) keV
| style="text-align:center" | 1975
| 630(20) ns
| IT
| 141Pm
| 11/2−
|
|-id=Promethium-141m2
| style="text-indent:1em" | 141m2Pm
| colspan="3" style="text-indent:2em" | 2530.75(17) keV
| style="text-align:center" | 1985
| >2 μs
| IT
| 141Pm
| (23/2+)
|
|-id=Promethium-142
| rowspan=2|142Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 81
| rowspan=2|141.912891(25)
| rowspan=2 style="text-align:center" | 1959
| rowspan=2|40.5(5) s
| β+ (77.1%)
| rowspan=2|142Nd
| rowspan=2|1+
| rowspan=2|
|-
| EC (22.9%)
|-id=Promethium-142m1
| style="text-indent:1em" | 142m1Pm
| colspan="3" style="text-indent:2em" | 883.17(16) keV
| style="text-align:center" | 1971
| 2.0(2) ms
| IT
| 142Pm
| (8)−
|
|-id=Promethium-142m2
| style="text-indent:1em" | 142m2Pm
| colspan="3" style="text-indent:2em" | 2828.7(6) keV
| style="text-align:center" | 2004
| 67(5) μs
| IT
| 142Pm
| (13−)
|
|-id=Promethium-143
| rowspan=2|143Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 82
| rowspan=2 | 142.9109381(32)
| rowspan=2 style="text-align:center" | 1952
| rowspan=2 | 265(7) d
| EC
| rowspan=2 | 143Nd
| rowspan=2 | 5/2+
| rowspan=2 |
|-
| β+ (<5.7×10−6%)
|-id=Promethium-144
| rowspan=2|144Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 83
| rowspan=2 | 143.9125962(31)
| rowspan=2 style="text-align:center" | 1952
| rowspan=2 | 363(14) d
| EC
| rowspan=2 | 144Nd
| rowspan=2 | 5−
| rowspan=2 |
|-
| β+ (<8×10−5%)
|-id=Promethium-144m1
| style="text-indent:1em" | 144m1Pm
| colspan="3" style="text-indent:2em" | 840.90(5) keV
| style="text-align:center" | 1976
| 780(200) ns
| IT
| 144Pm
| (9)+
|
|-id=Promethium-144m2
| style="text-indent:1em" | 144m2Pm
| colspan="3" style="text-indent:2em" | 8595.8(22) keV
| style="text-align:center" | (1994)[n 4]
| ~2.7 μs
| IT
| 144Pm
| (27+)
|
|-id=Promethium-145
| rowspan=2|145Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 84
| rowspan=2|144.9127557(30)
| rowspan=2 style="text-align:center" | 1951
| rowspan=2|17.7(4) y
| EC
| 145Nd
| rowspan=2|5/2+
| rowspan=2|
|-
| α (2.8×10−7%)
| 141Pr
|-id=Promethium-146
| rowspan=2|146Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 85
| rowspan=2|145.9147022(46)
| rowspan=2 style="text-align:center" | 1960
| rowspan=2|5.53(5) y
| EC (66.0%)
| 146Nd
| rowspan=2|3−
| rowspan=2|
|-
| β− (34.0%)
| 146Sm
|-id=Promethium-147
| 147Pm[n 5]
| style="text-align:right" | 61
| style="text-align:right" | 86
| 146.9151449(14)
| style="text-align:center" | 1947
| 2.6234(2) y
| β−
| 147Sm
| 7/2+
| Trace[n 6]
|-id=Promethium-148
| 148Pm
| style="text-align:right" | 61
| style="text-align:right" | 87
| 147.9174811(61)
| style="text-align:center" | 1947
| 5.368(7) d
| β−
| 148Sm
| 1−
|
|-id=Promethium-148m
| rowspan=2 style="text-indent:1em" | 148mPm
| rowspan=2 colspan="3" style="text-indent:2em" | 137.9(3) keV
| rowspan=2 style="text-align:center" | 1952
| rowspan=2|41.29(11) d
| β− (95.8%)
| 148Sm
| rowspan=2|5−, 6−
| rowspan=2|
|-
| IT (4.2%)
| 148Pm
|-id=Promethium-149
| 149Pm[n 5]
| style="text-align:right" | 61
| style="text-align:right" | 88
| 148.9183415(23)
| style="text-align:center" | 1947
| 53.08(5) h
| β−
| 149Sm
| 7/2+
|
|-id=Promethium-149m
| style="text-indent:1em" | 149mPm
| colspan="3" style="text-indent:2em" | 240.214(7) keV
| style="text-align:center" | 1966
| 35(3) μs
| IT
| 149Pm
| 11/2−
|
|-id=Promethium-150
| 150Pm
| style="text-align:right" | 61
| style="text-align:right" | 89
| 149.920990(22)
| style="text-align:center" | 1952
| 2.698(15) h
| β−
| 150Sm
| (1−)
|
|-id=Promethium-151
| 151Pm[n 5]
| style="text-align:right" | 61
| style="text-align:right" | 90
| 150.9212166(49)
| style="text-align:center" | 1952
| 28.40(4) h
| β−
| 151Sm
| 5/2+
|
|-id=Promethium-152
| 152Pm
| style="text-align:right" | 61
| style="text-align:right" | 91
| 151.923505(28)
| style="text-align:center" | 1958
| 4.12(8) min
| β−
| 152Sm
| 1+
|
|-id=Promethium-152m1
| style="text-indent:1em" | 152m1Pm
| colspan="3" style="text-indent:2em" | 140(90) keV[n 2]
| style="text-align:center" | 1969
| 7.52(8) min
| β−
| 152Sm
| 4(−)
|
|-id=Promethium-152m2
| rowspan=2 style="text-indent:1em" | 152m2Pm
| rowspan=2 colspan="3" style="text-indent:2em" | 150+x keV
| rowspan=2 style="text-align:center" | 1971
| rowspan=2|13.8(2) min
| β− (≤100%)
| 152Sm
| rowspan=2|(8)
| rowspan=2|
|-
| IT (≥0%)
| 152Pm
|-id=Promethium-153
| 153Pm
| style="text-align:right" | 61
| style="text-align:right" | 92
| 152.9241563(97)
| style="text-align:center" | 1962
| 5.25(2) min
| β−
| 153Sm
| 5/2−
|
|-id=Promethium-154
| 154Pm
| style="text-align:right" | 61
| style="text-align:right" | 93
| 153.926713(27)
| style="text-align:center" | 1958
| 2.68(7) min
| β−
| 154Sm
| (4+)
|
|-id=Promethium-154m
| style="text-indent:1em" | 154mPm[n 2]
| colspan="3" style="text-indent:2em" | −230(50) keV
| style="text-align:center" | 1971
| 1.73(10) min
| β−
| 154Sm
| (1−)
|
|-id=Promethium-155
| 155Pm
| style="text-align:right" | 61
| style="text-align:right" | 94
| 154.9281370(51)
| style="text-align:center" | 1982
| 41.5(2) s
| β−
| 155Sm
| (5/2−)
|
|-id=Promethium-156
| 156Pm
| style="text-align:right" | 61
| style="text-align:right" | 95
| 155.9311141(13)
| style="text-align:center" | 1986
| 27.4(5) s
| β−
| 156Sm
| 4+
|
|-id=Promethium-156m
| rowspan=2 style="text-indent:1em" | 156mPm
| rowspan=2 colspan="3" style="text-indent:2em" | 150.30(10) keV
| rowspan=2 style="text-align:center" | 2007
| rowspan=2|2.3(20) s
| IT (98%)
| 156Pm
| rowspan=2|1+#
| rowspan=2|
|-
| β− (2%)
| 156Sm
|-id=Promethium-157
| 157Pm
| style="text-align:right" | 61
| style="text-align:right" | 96
| 156.9331213(75)
| style="text-align:center" | 1987
| 10.56(10) s
| β−
| 157Sm
| (5/2−)
|
|-id=Promethium-158
| 158Pm
| style="text-align:right" | 61
| style="text-align:right" | 97
| 157.93654695(95)
| style="text-align:center" | 1987
| 4.8(5) s
| β−
| 158Sm
| (0+,1+)#
|
|-id=Promethium-158m
| style="text-indent:1em" | 158mPm
| colspan="3" style="text-indent:2em" | 150(50)# keV
| style="text-align:center" | (2015)[n 4]
| >16 μs
| IT
| 158Pm
| 5+#
|
|-id=Promethium-159
| 159Pm
| style="text-align:right" | 61
| style="text-align:right" | 98
| 158.939286(11)
| style="text-align:center" | 2005
| 1.648+0.043
−0.042 s[2]
| β−
| 159Sm
| (5/2−)
|
|-id=Promethium-159m
| rowspan=2 style="text-indent:1em" | 159mPm
| rowspan=2 colspan="3" style="text-indent:2em" | 1465.0(5) keV
| rowspan=2 style="text-align:center" | 2021
| rowspan=2|4.42(17) μs
| IT
| 159Pm
| rowspan=2|17/2+#
| rowspan=2|
|-
| β−, n (<0.6%)[2]
| 158Sm
|-id=Promethium-160
| rowspan=2|160Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 99
| rowspan=2|159.9432153(22)
| rowspan=2 style="text-align:center" | 2012
| rowspan=2|874+16
−12 ms[2]
| β−
| 160Sm
| rowspan=2|6−#
| rowspan=2|
|-
| β−, n (<0.1%)[2]
| 159Sm
|-id=Promethium-160m
| style="text-indent:1em" | 160mPm
| colspan="3" style="text-indent:2em" | 191(11) keV
| style="text-align:center" | 2020
| >700 ms
|
|
| 1−#
|
|-id=Promethium-161
| rowspan=2|161Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 100
| rowspan=2|160.9462298(97)
| rowspan=2 style="text-align:center" | 2012
| rowspan=2|724+20
−12 ms[2]
| β− (98.91%)
| 161Sm
| rowspan=2|(5/2−)
| rowspan=2|
|-
| β−, n (1.09%)[2]
| 160Sm
|-id=Promethium-161m
| style="text-indent:1em" | 161mPm
| colspan="3" style="text-indent:2em" | 965.9(9) keV
| style="text-align:center" | 2021
| 890(90) ns
| IT
| 161Pm
| (13/2+)
|
|-id=Promethium-162
| rowspan=2|162Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 101
| rowspan=2|161.95057(32)#
| rowspan=2 style="text-align:center" | 2012
| rowspan=2|467+38
−18 ms[2]
| β− (98.21%)
| 162Sm
| rowspan=2| 2+#
| rowspan=2|
|-
| β−, n (1.79%)[2]
| 161Sm
|-id=Promethium-163
| rowspan=2|163Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 102
| rowspan=2|162.95388(43)#
| rowspan=2 style="text-align:center" | 2012
| rowspan=2|362+42
−30 ms[2]
| β− (95%)
| 163Sm
| rowspan=2|5/2−#
| rowspan=2|
|-
| β−, n (5.00%)[2]
| 162Sm
|-id=Promethium-164
| rowspan=2|164Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 103
| rowspan=2|163.95882(43)#
| rowspan=2 style="text-align:center" | 2018
| rowspan=2|280+38
−33 ms[2]
| β− (93.82%)
| 164Sm
| rowspan=2|5−#
| rowspan=2|
|-
| β−, n (6.18%)[2]
| 163Sm
|-id=Promethium-165
| rowspan=2|165Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 104
| rowspan=2|164.96278(54)#
| rowspan=2 style="text-align:center" | 2018
| rowspan=2|297+111
−101 ms[2]
| β− (86.74%)
| 165Sm
| rowspan=2|5/2−#
| rowspan=2|
|-
| β−, n (13.26%)[2]
| 164Sm
|-id=Promethium-166
| rowspan=2|166Pm
| rowspan=2 style="text-align:right" | 61
| rowspan=2 style="text-align:right" | 105
| rowspan=2|
| rowspan=2 style="text-align:center" | 2022
| rowspan=2|228+131
−112 ms[2]
| β−
| 166Sm
| rowspan=2|
| rowspan=2|
|-
| β−, n (<52%)[2]
| 165Sm
Template:Isotopes table/footer
Stability of promethium isotopes
Script error: No such module "Labelled list hatnote". Promethium is one of the two elements of the first 82 elements that has no stable isotopes. This is a rarely occurring effect of the liquid drop model. Namely, promethium does not have any beta-stable isotopes, as for any mass number, it is energetically favorable for a promethium isotope to undergo positron emission or beta decay, respectively forming a neodymium or samarium isotope which has a higher binding energy per nucleon. The other element for which this happens is technetium (Z = 43).
Promethium-147
Promethium-147 beta decays to the long-lived primordial radioisotope samarium-147 with a half-life of 2.6234 years, emitting low-energy beta radiation without gamma emission. It is a common fission product, produced in nuclear reactors and in trace quantities in nature, where it is also produced by the alpha decay of europium-151.[3]
In the reactor environment, it is almost exclusively produced through beta decay of neodymium-147 as usual for fission products. The isotopes 142-146Nd, 148Nd, and 150Nd are all stable with respect to beta decay, so the isotopes of promethium with those masses are not produced by beta decay and are therefore not significant fission products (as they could only be produced directly, rather than through a beta-decay chain). 149Pm and 151Pm are, but have half-lives of only 53.08 and 28.40 hours, so are not found in spent nuclear fuel that has been cooled for months or years.
Promethium-147 is used as a beta particle source and a radioisotope thermoelectric generator (RTG) fuel; its power density is about 2 watts per gram. Mixed with a phosphor, it was used to illuminate the Apollo Lunar Module electrical switch tips and the control panels of the Lunar Roving Vehicle.[4] For luminescent applications, it has generally been replaced by tritium, which is even safer and has a longer half-life (12.32 years).
See also
Daughter products other than promethium
References
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- ^ a b c Page Module:Citation/CS1/styles.css has no content.Suzuki, H; Fukuda, N; Takeda, H; Shimizu, Y; Yoshimoto, M; Togano, Y; Sato, H; Kitamura, N; Hanai, S; Momota, S; Kusaka, K; Yanagisawa, Y; Ohtake, M; Sumikama, T; Fukunishi, N; Michimasa, S (7 November 2025). "Discovery of Proton-Rich Radioactive Isotopes in the Z = 60 Region Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 238U Beam". Progress of Theoretical and Experimental Physics. 2025 (11). doi:10.1093/ptep/ptaf149.
- ^ a b c d e f g h i j k l m n o p Page Module:Citation/CS1/styles.css has no content.Kiss, G. G.; Vitéz-Sveiczer, A.; Saito, Y.; et al. (2022). "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". The Astrophysical Journal. 936 (107): 107. Bibcode:2022ApJ...936..107K. doi:10.3847/1538-4357/ac80fc. hdl:2117/375253.
- ^ Page Module:Citation/CS1/styles.css has no content.Belli, P.; Bernabei, R.; Cappella, F.; et al. (2007). "Search for α decay of natural Europium". Nuclear Physics A. 789 (1–4): 15–29. Bibcode:2007NuPhA.789...15B. doi:10.1016/j.nuclphysa.2007.03.001.
- ^ Page Module:Citation/CS1/styles.css has no content."Apollo Experience Report - Protection Against Radiation" (PDF). NASA. Archived from the original (PDF) on 14 November 2014. Retrieved 9 December 2011.
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