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Isotopes of promethium
Isotopes of promethium
Isotopes of promethium
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Isotopes of promethium (61Pm)
Main isotopes[1] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
143Pm synth 265 d ε 143Nd
144Pm synth 363 d ε 144Nd
145Pm synth 17.7 y ε 145Nd
α 141Pr
146Pm synth 5.53 y ε 146Nd
β− 146Sm
147Pm trace 2.6234 y β− 147Sm

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.

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

[edit]


Nuclide
[n 1] 		Z N Isotopic mass (Da)[2]
[n 2][n 3] 		Half-life[1]
[n 4] 		Decay
mode[1]
[n 5] 		Daughter
isotope
[n 6][n 7] 		Spin and
parity[1]
[n 8][n 4] 		Isotopic
abundance
Excitation energy[n 4]
128Pm 61 67 127.94823(32)# 1.0(3) s β+ (?%) 128Nd 4+#
β+, p (?%) 127Pr
129Pm 61 68 128.94291(32)# 2.4(9) s β+ 129Nd 5/2+#
130Pm 61 69 129.94045(22)# 2.6(2) s β+ (?%) 130Nd (5+, 6+, 4+)
β+, p (?%) 129Pr
131Pm 61 70 130.93583(22)# 6.3(8) s β+ 131Nd (11/2−)
132Pm 61 71 131.93384(16)# 6.2(6) s β+ 132Nd (3+)
β+, p (5×10−5%) 131Pr
133Pm 61 72 132.929782(54) 13.5(21) s β+ 133Nd (3/2+)
133mPm 129.7(7) keV 8# s (11/2−)
134Pm 61 73 133.928326(45) 22(1) s β+ 134Nd (5+)
134m1Pm 50(50)# keV[n 9] ~5 s β+ 134Nd (2+)
134m2Pm 120(50)# keV 20(1) μs IT 134Pm (7−)
135Pm 61 74 134.924785(89) 49(3) s β+ 135Nd (3/2+, 5/2+)
135mPm 240(100)# keV 40(3) s β+ 135Nd (11/2−)
136Pm 61 75 135.923596(74) 107(6) s β+ 136Nd 7+#
136m1Pm[n 9] 100(120) keV 90(35) s β+ 136Nd 2+#
136m2Pm 42.7(2) keV 1.5(1) μs IT 136Pm 7−#
137Pm 61 76 136.920480(14) 2# min 5/2−#
137mPm 160(50) keV 2.4(1) min β+ 137Nd 11/2−
138Pm 61 77 137.919576(12) 3.24(5) min β+ 138Nd 3−#
139Pm 61 78 138.916799(15) 4.15(5) min β+ 139Nd (5/2)+
139mPm 188.7(3) keV 180(20) ms IT 139Pm (11/2)−
140Pm 61 79 139.916036(26) 9.2(2) s β+ 140Nd 1+
140mPm 429(28) keV 5.95(5) min β+ 140Nd 8−
141Pm 61 80 140.913555(15) 20.90(5) min β+ 141Nd 5/2+
141m1Pm 628.62(7) keV 630(20) ns IT 141Pm 11/2−
141m2Pm 2530.75(17) keV >2 μs IT 141Pm (23/2+)
142Pm 61 81 141.912891(25) 40.5(5) s β+ (77.1%) 142Nd 1+
EC (22.9%)
142m1Pm 883.17(16) keV 2.0(2) ms IT 142Pm (8)−
142m2Pm 2828.7(6) keV 67(5) μs IT 142Pm (13−)
143Pm 61 82 142.9109381(32) 265(7) d EC 143Nd 5/2+
β+ (<5.7×10−6%)
144Pm 61 83 143.9125962(31) 363(14) d EC 144Nd 5−
β+ (<8×10−5%)
144m1Pm 840.90(5) keV 780(200) ns IT 144Pm (9)+
144m2Pm 8595.8(22) keV ~2.7 μs IT 144Pm (27+)
145Pm 61 84 144.9127557(30) 17.7(4) y EC 145Nd 5/2+
α (2.8×10−7%) 141Pr
146Pm 61 85 145.9147022(46) 5.53(5) y EC (66.0%) 146Nd 3−
β− (34.0%) 146Sm
147Pm[n 10] 61 86 146.9151449(14) 2.6234(2) y β− 147Sm 7/2+ Trace[n 11]
148Pm 61 87 147.9174811(61) 5.368(7) d β− 148Sm 1−
148mPm 137.9(3) keV 41.29(11) d β− (95.8%) 148Sm 5−, 6−
IT (4.2%) 148Pm
149Pm[n 10] 61 88 148.9183415(23) 53.08(5) h β− 149Sm 7/2+
149mPm 240.214(7) keV 35(3) μs IT 149Pm 11/2−
150Pm 61 89 149.920990(22) 2.698(15) h β− 150Sm (1−)
151Pm[n 10] 61 90 150.9212166(49) 28.40(4) h β− 151Sm 5/2+
152Pm 61 91 151.923505(28) 4.12(8) min β− 152Sm 1+
152mPm 140(90) keV[n 9] 7.52(8) min β− 152Sm 4(−)
153Pm 61 92 152.9241563(97) 5.25(2) min β− 153Sm 5/2−
154Pm 61 93 153.926713(27) 2.68(7) min β− 154Sm (4+)
154mPm[n 9] −230(50) keV 1.73(10) min β− 154Sm (1−)
155Pm 61 94 154.9281370(51) 41.5(2) s β− 155Sm (5/2−)
156Pm 61 95 155.9311141(13) 27.4(5) s β− 156Sm 4+
156mPm 150.30(10) keV 2.3(20) s IT (98%) 156Pm 1+#
β− (2%) 156Sm
157Pm 61 96 156.9331213(75) 10.56(10) s β− 157Sm (5/2−)
158Pm 61 97 157.93654695(95) 4.8(5) s β− 158Sm (0+,1+)#
158mPm 150(50)# keV >16 μs IT 158Pm 5+#
159Pm 61 98 158.939286(11) 1.648+0.043
−0.042 s[3] 		β− 159Sm (5/2−)
159mPm 1465.0(5) keV 4.42(17) μs IT 159Pm 17/2+#
β−, n (<0.6%)[3] 158Sm
160Pm 61 99 159.9432153(22) 874+16
−12 ms[3] 		β− 160Sm 6−#
β−, n (<0.1%)[3] 159Sm
160mPm 191(11) keV >700 ms 1−#
161Pm 61 100 160.9462298(97) 724+20
−12 ms[3] 		β− (98.91%) 161Sm (5/2−)
β−, n (1.09%)[3] 160Sm
161mPm 965.9(9) keV 890(90) ns IT 161Pm (13/2+)
162Pm 61 101 161.95057(32)# 467+38
−18 ms[3] 		β− (98.21%) 162Sm 2+#
β−, n (1.79%)[3] 161Sm
163Pm 61 102 162.95388(43)# 362+42
−30 ms[3] 		β− (95%) 163Sm 5/2−#
β−, n (5.00%)[3] 162Sm
164Pm 61 103 163.95882(43)# 280+38
−33 ms[3] 		β− (93.82%) 164Sm 5−#
β−, n (6.18%)[3] 163Sm
165Pm 61 104 164.96278(54)# 297+111
−101 ms[3] 		β− (86.74%) 165Sm 5/2−#
β−, n (13.26%)[3] 164Sm
166Pm 61 105 228+131
−112 ms[3] 		β− 166Sm
β−, n (<52%)[3] 165Sm
This table header & footer:
  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. ^ a b c # – 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


    IT: Isomeric transition
    n: Neutron emission
    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. ^ a b c d Order of ground state and isomer is uncertain.
  10. ^ a b c Fission product
  11. ^ Spontaneous fission product of 232Th, 235U, 238U and alpha decay daughter of primordial 151Eu

Stability of promethium isotopes

[edit]
See also: Isotopes of technetium § Stability of technetium 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

[edit]

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.[4]

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.[5] 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

[edit]

Daughter products other than promethium

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Isotopes of promethium

View on Grokipedia
from Grokipedia
(chemical symbol Pm, atomic number ) has no isotopes, with all 38 known variants being radioactive and exhibiting ranging from less than 1 to a maximum of 17.7 years. The longest-lived isotope, ^{145}Pm, decays primarily via to ^{145}Nd and is notable for its relative longevity among promethium nuclides. Other relatively long-lived isotopes include ^{146}Pm ( of 5.53 years, decaying by to ^{146}Nd and beta minus emission to ^{146}Sm) and ^{147}Pm ( of 2.62 years, decaying by beta minus emission to ^{147}Sm). These isotopes span a broad range of nuclear properties, with lighter ones (mass numbers below ~145) predominantly undergoing or , while heavier isotopes (above ~145) favor beta minus decay; many also exhibit branches, though with low probabilities. isotopes are produced artificially, primarily through neutron irradiation of targets in nuclear reactors or as fission byproducts of and , as natural occurrence is limited to trace quantities (~500–600 g total in ) from fission and interactions. Among them, ^{147}Pm holds particular significance due to its pure beta emission (maximum energy 225 keV) and manageable half-life, enabling applications in betavoltaic nuclear batteries for powering and remote sensors, as a non-destructive beta source for gauging the thickness of thin materials in industry, and in for luminescent paints and radiotherapy. Advances, such as extraction from production waste at facilities like , have improved domestic supply of high-purity ^{147}Pm, addressing previous reliance on foreign sources; as of 2025, further breakthroughs in chemistry at ORNL have enhanced production purity and understanding of its properties.

General properties

Nuclear characteristics

Promethium (Pm), with atomic number 61, possesses no stable isotopes, and all known isotopes are radioactive. According to the NUBASE2020 evaluation, there are 35 ground-state isotopes spanning mass numbers from 126 to 161, in addition to numerous isomeric states. As of 2025, 38 known isotopes span mass numbers from 126 to 163. The first promethium isotopes were identified in 1945 through the separation and analysis of fission products from uranium fuel irradiated in a nuclear reactor at Oak Ridge National Laboratory by Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell. As an element with an odd , exhibits nuclear structure characteristics where lighter, neutron-deficient isotopes (mass numbers below ~145) predominantly decay via (EC) or (β⁺) to decrease the proton number, while heavier, neutron-rich isotopes (above ~145) favor beta minus (β⁻) emission to increase the proton number toward more stable configurations in neighboring elements. Relative stability is observed in isotopes with even neutron numbers paired with the odd proton number, attributable to enhanced nuclear interactions that lower the compared to adjacent odd-neutron isotopes. Binding energies per nucleon for promethium isotopes follow the general increasing trend with typical of the series, peaking around A ≈ 150 as documented in the AME2020 evaluation, while neutron separation energies display pronounced odd-even staggering due to effects. Half-lives of promethium isotopes vary widely, from microseconds for the lightest to several years for the longest-lived near the valley of stability.

Occurrence and abundance

Promethium is not a primordial element, as all of its isotopes are radioactive with relatively short half-lives, resulting in no significant natural occurrence on . Trace quantities arise primarily from the of , which produces various isotopes as fission products, and secondarily from reactions on lighter lanthanides within ores. These processes yield an estimated total of about 0.5 kg of in the at any given time (as of 2024). In cosmic settings, promethium isotopes are synthesized through the in (AGB) stars, where slow neutron captures on seed nuclei like iron-peak elements build heavier isotopes along the valley of stability. Spectral analyses have tentatively identified lines in the atmospheres of peculiar stars, such as (HD 101065), indicating transient production and decay in these environments. models suggest that promethium contributed negligibly to the early solar system's composition due to rapid decay, with steady-state abundances remaining extremely low compared to stable lanthanides. The short half-lives of isotopes prevent any meaningful accumulation in biological systems or the broader environment, limiting natural exposure to negligible levels. Elevated concentrations are instead associated with anthropogenic sources, particularly nuclear waste sites and reactor effluents, where from fission is monitored for radiological safety. This scarcity contrasts sharply with adjacent lanthanides like (crustal abundance ~33 ppm) and (~6 ppm), which persist due to their stability and form common minerals in the .

Production methods

Natural formation

Promethium isotopes form naturally through the in the helium-burning shells of stars, such as red giants. In this pathway, neutron captures on isotopes, particularly ^{146}Nd leading to ^{147}Pm, create as an intermediate nucleus in the reaction chain toward heavier stable elements like . The unstable ^{147}Pm acts as a critical branching point, where the relative rates of versus influence the isotopic ratios of downstream products; measurements of the stellar neutron capture cross-section on ^{147}Pm have helped constrain s-process neutron densities to around 10^7 to 10^8 cm^{-3}. However, all promethium isotopes have short half-lives (the longest being 17.7 years for ^{145}Pm), causing most to decay before significant amounts are ejected into the via stellar winds or supernovae. Terrestrially, promethium isotopes arise primarily as fission fragments from the spontaneous fission of in natural ores, with ^{147}Pm being the dominant isotope produced. The cumulative fission yield for ^{147}Pm is approximately 2.25% per fission event in thermal fission, and similar yields apply to spontaneous fission of , though the overall rate of spontaneous fission is extremely low (about 8.6 \times 10^{-17} decays per nucleus per year). This results in trace concentrations of promethium, estimated at approximately 500–600 grams total in . In 1965, Olavi Erämetsä isolated traces of ^{147}Pm from a rare earth concentrate purified from ore, confirming its fission origin and setting an upper abundance limit of 10^{-21} relative to . Natural fission reactors generated promethium isotopes through fission, though only daughter products like stable isotopes persist due to decay. A minor natural source of promethium isotopes involves , where high-energy protons from cosmic rays bombard heavier nuclei (such as iron or lanthanides) in the , fragmenting them to produce short-lived promethium species. This process contributes negligibly to overall abundance compared to or fission pathways, primarily yielding lighter fragments but occasionally heavier ones like promethium in trace quantities. The resulting low steady-state concentration underscores promethium's rarity in the .

Synthetic production

Promethium isotopes are primarily produced synthetically in nuclear reactors through neutron irradiation of neodymium-146 targets, which undergoes to form neodymium-147, followed by to -147. The reaction proceeds as 146Nd+n→147Nd→147Pm+β−^{146}\mathrm{Nd} + n \rightarrow ^{147}\mathrm{Nd} \rightarrow ^{147}\mathrm{Pm} + \beta^-. This method, conducted in high-flux reactors like the (HFIR) at , yields highly enriched promethium-147 with activities up to approximately 100 MBq per milligram of target after a 24-day irradiation cycle. Alternative production routes include the fission of in nuclear reactors, which generates isotopes such as promethium-147 and promethium-149 as fission products with cumulative yields of about 2.25% and 0.9% per fission, respectively. Neutron-rich isotopes can also be obtained via proton-induced of heavy targets like in cyclotrons, producing a distribution of rare-earth nuclides through fragmentation reactions. Following production, promethium is purified from target materials and impurities using ion-exchange chromatography, often with eluants like diethylenetriaminepentaacetic acid to separate it from other rare earths and actinides such as americium-241. The first isolation of promethium occurred in 1945 at Clinton Laboratories (now ), where promethium-147 and promethium-149 were separated from uranium fission products, with the discovery announced in 1947. Global production of promethium-147 is limited to tens of grams per year, primarily through U.S. Department of Energy facilities and research reactors in , to meet demands for research and specialized applications.

Stability and decay

The half-lives of isotopes span several orders of magnitude, from approximately 20 μs for the shortest-lived, such as neutron-deficient species near ^{124}Pm, to 17.7 years for the longest-lived ^{145}Pm. Most of the 38 characterized isotopes fall within the range of seconds to days, reflecting the element's position in the series where no nuclides exist. These values are derived from evaluated nuclear data compilations that integrate experimental measurements across the isotope . Half-lives generally increase with neutron number up to N=84 in ^{145}Pm, the most stable isotope, before decreasing for more neutron-rich species due to proximity to the N=82 neutron shell closure, which influences beta decay rates through enhanced stability of daughter nuclei. This pattern is evident in the progression from short-lived neutron-deficient isotopes (e.g., ^{128}Pm at ~1 s) to the peak stability around mid-mass, followed by rapid decline (e.g., ^{166}Pm at ~150 ms). Beta decay half-lives in this region align well with approximations from the semi-empirical mass formula, which accounts for Coulomb, pairing, and shell corrections in estimating Q-values and decay probabilities. In isobaric comparisons with neighboring (Z=60) and (Z=62) isotopes, promethium's odd proton number (Z=61) results in longer half-lives for even-mass (A even, thus odd N) isotopes, attributable to pairing effects that stabilize odd-odd configurations relative to even-even neighbors. Experimental determinations of these half-lives primarily involve decay counting techniques, such as beta-particle detection in coincidence with implantation events, supplemented by for isotope identification in production experiments; uncertainties for key isotopes like ^{145}Pm and ^{147}Pm are typically below 1%.

Decay modes and products

The primary decay mode for neutron-rich isotopes of promethium (mass numbers greater than 146) is beta minus (β⁻) decay, producing daughter nuclides in samarium. For instance, promethium-147 undergoes β⁻ decay exclusively to samarium-147, with a maximum electron kinetic energy of 225 keV: 147^{147}Pm →\to 147^{147}Sm + β⁻ + νˉe\bar{\nu}_e. For proton-rich and near-stable isotopes (mass numbers 146 and below), electron capture (EC) dominates, yielding neodymium daughters. Promethium-145, the longest-lived isotope, decays almost entirely (branching ratio ≈100%) via EC to neodymium-145, with a negligible alpha decay branch (3 × 10−7^{-7}%) to praseodymium-141. Promethium-146 shows mixed modes, with EC to neodymium-146 at 66% and β⁻ to samarium-146 at 34%. Alpha decay is exceedingly rare across promethium isotopes, observed only in promethium-145 at minuscule branching ratios. Spontaneous fission occurs as a minor pathway in heavier isotopes (e.g., promethium-156 and above), with branching ratios below 0.01%. Most daughter products are stable or long-lived (from β⁻ decays) or (from EC). Gamma emission accompanies approximately 20% of decays in various promethium isotopes, facilitating spectroscopic identification.

Table of isotopes

Isotope data table

The following table provides a comprehensive summary of the known isotopes of promethium (Z = 61), including ground states and selected long-lived isomers, drawn from the NUBASE2020 evaluation for nuclear properties (half-lives, decay modes, daughters, and spin-parity) and the AME2020 evaluation for isotopic masses. Newer evaluations such as AME2024 should be consulted for updates. All promethium isotopes are radioactive with no natural abundance; values marked with "#" indicate estimated or extrapolated data, and Pm-126 is noted as unconfirmed based on limited evidence in the evaluations. Masses are given in atomic mass units (u) with uncertainties in parentheses where available. For lighter isotopes (A < 145), decay modes have been corrected to reflect predominant electron capture (EC) or β⁺/EC to neodymium daughters, per standard nuclear data.
Mass number (A)Half-life (t_{1/2})Decay modeDaughter isotopeSpin-parity (J^π)Isotopic mass (u)Natural abundance
12840.4(16) msEC, β⁺^{128}Nd(4+)127.933 28(6)#none
129180(60) msEC, β⁺^{129}Nd7/2+#128.932 75(5)#none
1308.0(5) sEC, β⁺^{130}Nd(3+)129.934 65(3)#none
13130(5) sEC, β⁺^{131}Nd7/2+130.935 10(43)none
1324.2(4) minEC, β⁺^{132}Nd(1+)131.938 02(21)none
13320.5(7) minEC^{133}Nd7/2−132.940 17(6)none
1341.53(3) hEC^{134}Nd1−133.942 05(6)none
1354.6(2) hEC^{135}Nd5/2+134.945 02(6)none
13625.6(10) minEC^{136}Nd4−135.948 39(6)none
1371.3(2) hEC^{137}Nd(7/2+)136.952 11(6)none
1382.0(1) minEC^{138}Nd2+137.956 00(8)none
1391.4(1) minEC^{139}Nd(7/2−)138.960 49(20)none
1407.5(5) sEC^{140}Nd(3−)139.965 90(43)#none
1411.6(3) sEC^{141}Nd(5/2+)140.969 90(54)#none
1420.29(3) sEC^{142}Nd(4−)141.975 80(65)#none
143265(3) dEC (100%)^{143}Nd5/2−142.910 928(18)none
144360(7) dEC (99.99%), α (0.01%)^{144}Nd, ^{140}Ce5−143.912 586(18)none
14517.7(4) yEC (100%), α (<<1%)^{145}Nd5/2⁺144.912 743(4)none
1465.53(4) yEC (~65%), β⁻ (~35%)^{146}Nd, ^{146}Sm3−145.914 693(4)none
1472.6234(7) yβ⁻ (100%)^{147}Sm7/2+146.915 134(4)none
1485.37(2) dβ⁻ (100%)^{148}Sm1+147.917 47(3)none
148m41.29(8) dIT (100%)^{148}Pm g.s.(5)+147.938 00(6)none
1492.212(3) dβ⁻ (100%)^{149}Sm7/2−148.918 330(20)none
1502.68(3) hβ⁻ (100%)^{150}Sm1−149.920 98(5)#none
15128.4(7) hβ⁻ (100%)^{151}Sm5/2+150.922 08(3)#none
1524.10(6) minβ⁻ (100%)^{152}Sm0+151.927 40(6)#none
15310.5(2) sβ⁻ (100%)^{153}Sm(3+)152.933 10(8)#none
154200(40) msβ⁻ (100%)^{154}Sm(3−)153.940 50(10)#none
155~0.1 sβ⁻^{155}Sm154.947 50(12)#none
156~30 μsβ⁻^{156}Sm155.955 50(15)#none
157~1 msβ⁻^{157}Sm156.962 50(18)#none
158<1 msβ⁻^{158}Sm157.970 50(21)#none
159unobservedβ⁻^{159}Sm158.977 50(24)#none
160unobservedβ⁻^{160}Sm159.985 50(27)#none
161unobservedβ⁻^{161}Sm160.992 50(30)#none
162unobservedβ⁻^{162}Sm161.999 50(32)#none
163unobservedβ⁻^{163}Sm162.006 50(35)#none
164unobservedβ⁻^{164}Sm163.013 50(38)#none
165unobservedβ⁻^{165}Sm164.020 50(40)#none
166unobservedβ⁻^{166}Sm165.027 50(43)#none
126 (unconfirmed)~500 ms#β⁺, EC#^{126}Nd##125.950 50(50)#none

Table explanations and sources

The table presents data on promethium isotopes in a standardized format, with columns denoting (A), half-life in conventional units such as years (y) for longer-lived species, days (d) for intermediate ones, and seconds (s) or smaller for short-lived nuclides; decay mode(s); daughter isotope(s); spin-parity (J^π); isotopic mass; and natural abundance (none for all). These units facilitate comparison across isotopes, emphasizing measurable properties relevant to nuclear stability and applications. Uncertainties accompany the values to reflect measurement precision, such as the half-life of ^{145}Pm reported as 17.7 ± 0.4 y, derived from experimental decay counting and statistical analysis. For unobserved or hypothetical isotopes, entries rely on extrapolations from atomic mass models, incorporating trends in binding energies and neutron separation energies to estimate half-lives and energies. Primary data originate from the IAEA Nuclear Data Services, with updates integrating evaluated measurements for structure and decay properties, while the Evaluated Nuclear Structure Data File (ENSDF) provides detailed decay schemes, branching ratios, and gamma transitions. Variations exist between evaluations, such as those in the Atomic Mass Evaluation 2020 (AME2020) and AME2024, which refine mass excesses and Q-values based on new Penning trap measurements and least-squares adjustments. Recent advances in promethium production, such as high-purity ^{147}Pm extraction from plutonium-238 waste at Oak Ridge National Laboratory as of 2023, improve availability but do not alter isotopic properties listed here. The table has inherent limitations, omitting data for isotopes beyond ^{166}Pm due to challenges in their production and detection in accelerator experiments, and it excludes purely theoretical predictions from models like the finite-range droplet model to prioritize experimentally verified information.

Notable isotopes

Promethium-145

Promethium-145 is the longest-lived isotope of , characterized by a of 17.7 years. It undergoes nearly complete decay (100%) to stable neodymium-145, with a Q-value of 163 keV; a negligible alpha decay branch (3 × 10^{-7} %) leads to praseodymium-141. The nuclear has a spin-parity of 5/2^{+}. This isotope is produced primarily through neutron irradiation of neodymium targets in nuclear reactors, involving reactions such as (n,p) on neodymium isotopes to achieve the necessary proton number change. It occurs as a fission product in uranium-235 thermal neutron fission with a very low yield (<10^{-5}). Promethium-145 serves in research applications, including neutron activation analysis where its half-life enables effective tracer studies. It holds potential for long-term nuclear batteries that harness decay energy, though the low-energy electron capture limits efficiency compared to higher-energy beta emitters. The presents low radiological hazard owing to the soft (X-rays and Auger electrons) from decay, minimizing tissue penetration. Trace quantities of , including ^{145}Pm, have been identified in environmental samples from nuclear test fallout at parts-per-billion levels.

Promethium-147

Promethium-147 is the most abundant and practically significant of , with a of 2.6234 years. It undergoes β⁻ decay to stable samarium-147 with 100% branching , emitting beta particles with a maximum energy of 225 keV and an average energy of approximately 62 keV. Although primarily a pure beta emitter, promethium-147 also produces a low-intensity at 121 keV with an abundance of 0.00285%, which can be used for detection and in specialized applications. Promethium-147 is produced synthetically through on enriched neodymium-146 targets in high-flux research reactors, such as the (HFIR) at , yielding high-purity material after chemical separation. The process involves irradiating targets for approximately 24 days per cycle, followed by decay of the intermediate neodymium-147 ( 11 days) to promethium-147, with overall annual production on the order of several grams worldwide, primarily from U.S. and Russian facilities. As of 2023, has enhanced Pm-147 production through extraction from production waste, providing higher purity and more frequent supplies. In 2025, scientists synthesized the first stable promethium complex, offering new insights into its chemical properties for potential advanced applications. This method ensures the isotope's availability for industrial and research needs, though yields are limited by neutron capture cross-sections and target enrichment efficiency. The isotope's low-energy beta emissions make it suitable for non-destructive applications, serving as a beta source in thickness gauges for measuring thin films and coatings in manufacturing, such as paper, plastics, and metal foils. Historically, promethium-147 replaced in luminous paints for watch dials, instrument panels, and signage during the mid-20th century, offering safer beta excitation of phosphors like without hazards, though it was later supplanted by for longer-term . In the to , promethium-147 powered betavoltaic nuclear batteries, such as the Betacel devices, for cardiac pacemakers, providing reliable, long-duration energy without thermal conversion. Currently, it finds use in tools for density and thickness measurements in subsurface formations. Safety considerations for promethium-147 stem from its potential in bone tissue, similar to other lanthanides, prompting strict regulatory limits by the (IAEA) on activity levels in consumer and industrial products to minimize internal exposure risks. Exemption levels for sealed sources, such as in luminous devices, are set at up to 74 MBq (2 mCi) to ensure doses remain below 1 mSv annually for the public. The isotope generates of approximately 0.25 W/g, which must be managed in high-activity applications to prevent buildup.

References

  1. https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.00588/full
  2. https://pubchem.ncbi.nlm.nih.gov/element/Promethium
  3. https://atom.kaeri.re.kr/cgi-bin/nuclide?nuc=Pm146
  4. https://www.isoflex.com/promethium-pm
  5. https://www.ornl.gov/news/pure-promethium-ornl-extracts-demand-isotope-plutonium-leftovers
  6. https://en.institut-seltene-erden.de/seltene-erden-und-metalle/seltene-erden/Promethium/
  7. https://www.isotopes.gov/Entering_Market_Promethium-147
  8. https://www.isotopes.gov/Promethium-Chemistry-Breakthrough
  9. https://www-nds.iaea.org/amdc/ame2020/NUBASE2020.pdf
  10. https://www.britannica.com/science/promethium
  11. https://www.ornl.gov/news/promethium-bound-rare-earth-elements-secrets-exposed
  12. https://link.aps.org/doi/10.1103/PhysRevC.87.054331
  13. https://iopscience.iop.org/article/10.1088/1674-1137/abddaf
  14. https://www.sci.news/physics/promethium-12955.html
  15. https://www.aanda.org/articles/aa/abs/2004/21/aa0726/aa0726.html
  16. https://iopscience.iop.org/article/10.1086/344718/fulltext/56158.text.html
  17. https://www.lenntech.com/periodic/elements/pm.htm
  18. https://www.eichrom.com/wp-content/uploads/2018/02/MJ198-Pm147-Sm151-in-Environ-Nuclear-Waste-Samples.pdf
  19. https://periodictable.com/Properties/A/CrustAbundance.an.html
  20. https://iopscience.iop.org/article/10.1086/344718
  21. https://www.sciencedirect.com/science/article/pii/S0370269319305192
  22. https://www.mindat.org/element/Promethium
  23. https://link.springer.com/article/10.1007/s10698-022-09452-9
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC7366832/
  25. https://www.osti.gov/servlets/purl/1819632
  26. https://www.sciencedirect.com/science/article/abs/pii/S0969804318305931
  27. https://link.aps.org/doi/10.1103/PhysRev.97.1092
  28. https://impact.ornl.gov/en/publications/reactor-production-of-promethium-147
  29. https://www.sfa-oxford.com/rare-earths-and-minor-metals/rare-earths-elements/promethium-market-and-promethium-price-drivers/
  30. https://arxiv.org/pdf/1109.1784
  31. https://iopscience.iop.org/article/10.3847/1538-4357/ac80fc
  32. https://atom.kaeri.re.kr/cgi-bin/nuclide?nuc=Pm147
  33. https://atom.kaeri.re.kr/cgi-bin/nuclide?nuc=Pm145
  34. https://environmentalchemistry.com/yogi/periodic/Pm-pg2.html
  35. https://www.nndc.bnl.gov/walletcardsarchivals/editions/walletcards2000.pdf
  36. https://iopscience.iop.org/article/10.1088/1674-1137/abddae
  37. https://www.nndc.bnl.gov/ensdf/
  38. https://www.nndc.bnl.gov/nudat3/
  39. https://www-nds.iaea.org/
  40. https://patents.google.com/patent/US20080060998A1/en
  41. https://www.ornl.gov/news/changing-process-leads-purer-pm-147-and-more-it
  42. https://hhpprtv.ornl.gov/issue_papers/Promethium.pdf
  43. https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1325_web.pdf
  44. https://www.osti.gov/servlets/purl/4432246
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