Isotopes of promethium

Short description: Nuclides with atomic number of 61 but with different mass numbers

Main isotopes of Chemistry:promethium (61Pm) | Iso­tope | Decay

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| abun­dance | half-life (t1/2) | mode | pro­duct
145Pm  | trace | 17.7 y  | ε | 145Nd
146Pm  | syn | 5.53 y  | ε  | 146Nd
β− | 146Sm
147Pm  | trace  | 2.6234 y  | β− | 147Sm
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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.

Forty-one radioisotopes have been characterized, with the most stable being 145Pm with a half-life of 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm with a half-life of 2.6234 years. All of the remaining radioactive isotopes have half-lives that are less than 365 days, and the majority of these have half-lives that are less than 30 seconds. This element also has 18 meta states with the most stable being 148mPm (t1/2 41.29 days), 152m2Pm (t1/2 13.8 minutes) and 152mPm (t1/2 7.52 minutes).

The isotopes of promethium range in mass number from 126 to 166. The primary decay mode for 146Pm and lighter isotopes is electron capture, and the primary mode for heavier isotopes is beta decay. The primary decay products before 146Pm are isotopes of neodymium, and the primary products after are isotopes of samarium.

## Contents

* 1 List of isotopes
* 2 Stability of promethium isotopes
* 3 Promethium-147
* 4 References

## List of isotopes

Nuclide
[n 1] | Z | N | Isotopic mass (u)
[n 2][n 3] | Half-life
[n 4] | Decay
mode
[n 5] | Daughter
isotope
[n 6][n 7] | Spin and
parity
[n 8][n 4] | Isotopic
abundance

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Excitation energy[n 4]
126Pm  | 61  | 65  | 125.95752(54)#  | 0.5# s  |  |  |  |
127Pm  | 61  | 66  | 126.95163(64)#  | 1# s  |  |  | 5/2+#  |
128Pm  | 61  | 67  | 127.94842(43)#  | 1.0(3) s  | β+ | 128Nd  | 6+#  |
p | 127Nd
129Pm  | 61  | 68  | 128.94316(43)#  | 3# s [>200 ns]  | β+ | 129Nd  | 5/2+#  |
130Pm  | 61  | 69  | 129.94045(32)#  | 2.6(2) s  | β+ | 130Nd  | (5+, 6+, 4+)  |
β+, p (rare)  | 129Pr
131Pm  | 61  | 70  | 130.93587(21)#  | 6.3(8) s  | β+, p  | 130Pr  | 5/2+#  |
β+ | 131Nd
132Pm  | 61  | 71  | 131.93375(21)#  | 6.2(6) s  | β+ | 132Nd  | (3+)  |
β+, p (5×10−5%)  | 131Pr
133Pm  | 61  | 72  | 132.92978(5)  | 15(3) s  | β+ | 133Nd  | (3/2+)  |
133mPm  | 130.4(10) keV  | 10# s  | β+ | 133Nd  | (11/2−)  |
IT  | 133Pm
134Pm  | 61  | 73  | 133.92835(6)  | 22(1) s  | β+ | 134Nd  | (5+)  |
134mPm  | 0(100)# keV  | ~5 s  | IT  | 134Pm  | (2+)  |
135Pm  | 61  | 74  | 134.92488(6)  | 49(3) s  | β+ | 135Nd  | (5/2+, 3/2+)  |
135mPm  | 50(100)# keV  | 40(3) s  | β+ | 135Nd  | (11/2−)  |
136Pm  | 61  | 75  | 135.92357(8)  | 107(6) s  | β+ | 136Nd  | (5−)  |
136mPm  | 130(120) keV  | 47(2) s  | β+ | 136Nd  | (2+)  |
137Pm  | 61  | 76  | 136.920479(14)  | 2# min  | β+ | 137Nd  | 5/2+#  |
137mPm  | 150(50) keV  | 2.4(1) min  | β+ | 137Nd  | 11/2−  |
138Pm  | 61  | 77  | 137.919548(30)  | 10(2) s  | β+ | 138Nd  | 1+#  |
138mPm  | 30(30) keV  | 3.24(5) min  | β+ | 138Nd  | 5−#  |
139Pm  | 61  | 78  | 138.916804(14)  | 4.15(5) min  | β+ | 139Nd  | (5/2)+  |
139mPm  | 188.7(3) keV  | 180(20) ms  | IT (99.83%)  | 139Pm  | (11/2)−  |
β+ (0.17%)  | 139Nd
140Pm  | 61  | 79  | 139.91604(4)  | 9.2(2) s  | β+ | 140Nd  | 1+  |
140mPm  | 420(40) keV  | 5.95(5) min  | β+ | 140Nd  | 8−  |
141Pm  | 61  | 80  | 140.913555(15)  | 20.90(5) min  | β+ | 141Nd  | 5/2+  |
141m1Pm  | 628.40(10) keV  | 630(20) ns  |  |  | 11/2−  |
141m2Pm  | 2530.9(5) keV  | >2 µs  |  |  |  |
142Pm  | 61  | 81  | 141.912874(27)  | 40.5(5) s  | β+ | 142Nd | 1+  |
142mPm  | 883.17(16) keV  | 2.0(2) ms  | IT  | 142Pm  | (8)−  |
143Pm  | 61  | 82  | 142.910933(4)  | 265(7) d  | EC | 143Nd | 5/2+  |
β+ (<5.7×10−6%)[1]
144Pm  | 61  | 83  | 143.912591(3)  | 363(14) d  | EC  | 144Nd | 5−  |
β+ (<8×10−5%)[1]
144m1Pm  | 840.90(5) keV  | 780(200) ns  |  |  | (9)+  |
144m2Pm  | 8595.8(22) keV  | ~2.7 µs  |  |  | (27+)  |
145Pm  | 61  | 84  | 144.912749(3)  | 17.7(4) y  | EC  | 145Nd | 5/2+  |
α (2.8×10−7%)  | 141Pr
146Pm  | 61  | 85  | 145.914696(5)  | 5.53(5) y  | EC (66%)  | 146Nd | 3−  |
β− (34%)  | 146Sm
147Pm[n 9] | 61  | 86  | 146.9151385(26)  | 2.6234(2) y  | β− | 147Sm | 7/2+  | Trace[n 10]
148Pm  | 61  | 87  | 147.917475(7)  | 5.368(2) d  | β− | 148Sm | 1−  |
148mPm  | 137.9(3) keV  | 41.29(11) d  | β− (95%)  | 148Sm | 5−, 6−  |
IT (5%)  | 148Pm
149Pm[n 9] | 61  | 88  | 148.918334(4)  | 53.08(5) h  | β− | 149Sm | 7/2+  |
149mPm  | 240.214(7) keV  | 35(3) µs  |  |  | 11/2−  |
150Pm  | 61  | 89  | 149.920984(22)  | 2.68(2) h  | β− | 150Sm | (1−)  |
151Pm[n 9] | 61  | 90  | 150.921207(6)  | 28.40(4) h  | β− | 151Sm  | 5/2+  |
152Pm  | 61  | 91  | 151.923497(28)  | 4.12(8) min  | β− | 152Sm | 1+  |
152m1Pm  | 140(90) keV  | 7.52(8) min  |  |  | 4−  |
152m2Pm  | 250(150)# keV  | 13.8(2) min  |  |  | (8)  |
153Pm  | 61  | 92  | 152.924117(12)  | 5.25(2) min  | β− | 153Sm  | 5/2−  |
154Pm  | 61  | 93  | 153.92646(5)  | 1.73(10) min  | β− | 154Sm | (0, 1)  |
154mPm  | 120(120) keV  | 2.68(7) min  | β− | 154Sm | (3, 4)  |
155Pm  | 61  | 94  | 154.92810(3)  | 41.5(2) s  | β− | 155Sm  | (5/2−)  |
156Pm  | 61  | 95  | 155.93106(4)  | 26.70(10) s  | β− | 156Sm  | 4−  |
157Pm  | 61  | 96  | 156.93304(12)  | 10.56(10) s  | β− | 157Sm  | (5/2−)  |
158Pm  | 61  | 97  | 157.93656(14)  | 4.8(5) s  | β− | 158Sm  |  |
159Pm  | 61  | 98  | 158.93897(21)#  | 1.648+0.43
−0.42 s[2] | β− | 159Sm  | 5/2−#  |
160Pm  | 61  | 99  | 159.94299(32)#  | 874+16
−12 ms[2] | β− | 160Sm  |  |
161Pm  | 61  | 100  | 160.94586(54)#  | 724+20
−12 ms[2] | β− (98.91%)  | 161Sm  | 5/2−#  |
β−, n (1.09%)  | 160Sm
162Pm  | 61  | 101  | 161.95029(75)#  | 467+38
−18 ms[2] | β− (98.21%)  | 162Sm  |  |
β−, n (1.79%)  | 161Sm
163Pm  | 61  | 102  | 162.95368(86)#  | 362+42
−30 ms[2] | β− (95%)  | 163Sm  | 5/2−#  |
β−, n (1.79%)  | 162Sm
164Pm  | 61  | 103  |  | 280+38
−33 ms[2] | β− (93.82%)  | 164Sm  |  |
β−, n (6.18%)  | 163Sm
165Pm  | 61  | 104  |  | 297+111
−101 ms[2] | β− (86.74%)  | 165Sm  |  |
β−, n (13.26%)  | 164Sm
166Pm  | 61  | 105  |  | 228+131
−112 ms[2] | β− | 166Sm  |  |
β−, n  | 165Sm

1. ↑ mPm - Excited nuclear isomer.
2. ↑ ( ) - Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. ↑ # - Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. ↑ 4.0 4.1 4.2 # - Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. ↑ Modes of decay:  EC: | Electron capture

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IT: | Isomeric transition

p: | Proton emission
6. ↑ Bold italics symbol as daughter - Daughter product is nearly stable.
7. ↑ Bold symbol as daughter - Daughter product is stable.
8. ↑ ( ) spin value - Indicates spin with weak assignment arguments.
9. ↑ 9.0 9.1 9.2 Fission product
10. ↑ Alpha decay daughter of primordial 151Eu

## Stability of promethium isotopes

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 has a half-life of 2.62 years, and is a fission product produced in nuclear reactors via beta decay from neodymium-147. The isotopes 142Nd, 143Nd, 144Nd, 145Nd, 146Nd, 148Nd, and 150Nd are either stable or nearly so, so the isotopes of promethium with those masses cannot be produced by beta decay and therefore are not fission products in significant quantities. 149Pm and 151Pm 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. It is found naturally mostly from the spontaneous fission of uranium-238 and less often from the alpha decay of europium-151.[3]

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 Apollo Lunar Module electrical switch tips and painted on control panels of the Lunar Roving Vehicle.[4]

## References

1. ↑ 1.0 1.1 Cite error: Invalid `<ref>` tag; no text was provided for refs named `NUBASE2020`
2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Kiss, G. G.Expression error: Unrecognized word "et". (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. doi:10.3847/1538-4357/ac80fc. Bibcode: 2022ApJ...936..107K.
3. ↑ Belli, P.; Bernabei, R.; Cappella, F. et al. (2007). "Search for α decay of natural Europium". Nuclear Physics A 789 (1–4): 15–29. doi:10.1016/j.nuclphysa.2007.03.001. Bibcode: 2007NuPhA.789...15B.
4. ↑ "Apollo Experience Report - Protection Against Radiation". NASA. http://www.hq.nasa.gov/alsj/tnD7080RadProtect.pdf.

* 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, doi:10.1016/j.nuclphysa.2003.11.001, Bibcode: 2003NuPhA.729....3A, https://hal.archives-ouvertes.fr/in2p3-00020241/document
* Isotopic compositions and standard atomic masses from:
* 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.
* 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, doi:10.1016/j.nuclphysa.2003.11.001, Bibcode: 2003NuPhA.729....3A, https://hal.archives-ouvertes.fr/in2p3-00020241/document
* National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/.
* Lide, David R., ed (2004). "11. Table of the Isotopes". CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

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