Isotopes of promethium

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Isotopes of promethium  (61Pm)
Main isotopes [1] Decay
abun­dance half-life (t1/2) mode pro­duct
143Pm synth 265 d ε 143Nd
144Pmsynth363 dε 144Nd
145Pmsynth17.7 yε 145Nd
α 141Pr
146Pmsynth5.53 yε [2] 146Nd
β 146Sm
147Pm trace 2.6234 yβ 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.

Contents

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.

List of isotopes


Nuclide
[n 1]
Z N Isotopic mass (Da) [3]
[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]
128Pm6167127.94823(32)#1.0(3) s β+ (?%)128Nd4+#
β+, p (?%)127Pr
129Pm6168128.94291(32)#2.4(9) sβ+129Nd5/2+#
130Pm6169129.94045(22)#2.6(2) sβ+ (?%)130Nd(5+, 6+, 4+)
β+, p (?%)129Pr
131Pm6170130.93583(22)#6.3(8) sβ+131Nd(11/2−)
132Pm6171131.93384(16)#6.2(6) sβ+132Nd(3+)
β+, p (5×10−5%)131Pr
133Pm6172132.929782(54)13.5(21) sβ+133Nd(3/2+)
133mPm129.7(7) keV8# s(11/2−)
134Pm6173133.928326(45)22(1) sβ+134Nd(5+)
134m1Pm50(50)# keV [n 9] ~5 sβ+134Nd(2+)
134m2Pm120(50)# keV20(1) μs IT 134Pm(7−)
135Pm6174134.924785(89)49(3) sβ+135Nd(3/2+, 5/2+)
135mPm240(100)# keV40(3) sβ+135Nd(11/2−)
136Pm6175135.923596(74)107(6) sβ+136Nd7+#
136m1Pm [n 9] 100(120) keV90(35) sβ+136Nd2+#
136m2Pm42.7(2) keV1.5(1) μsIT136Pm7−#
137Pm6176136.920480(14)2# min5/2−#
137mPm160(50) keV2.4(1) minβ+137Nd11/2−
138Pm6177137.919576(12)3.24(5) minβ+138Nd3−#
139Pm6178138.916799(15)4.15(5) minβ+139Nd(5/2)+
139mPm188.7(3) keV180(20) msIT139Pm(11/2)−
140Pm6179139.916036(26)9.2(2) sβ+140Nd1+
140mPm429(28) keV5.95(5) minβ+140Nd8−
141Pm6180140.913555(15)20.90(5) minβ+141Nd5/2+
141m1Pm628.62(7) keV630(20) nsIT141Pm11/2−
141m2Pm2530.75(17) keV>2 μsIT141Pm(23/2+)
142Pm6181141.912891(25)40.5(5) sβ+ (77.1%)142Nd1+
EC (22.9%)
142m1Pm883.17(16) keV2.0(2) msIT142Pm(8)−
142m2Pm2828.7(6) keV67(5) μsIT142Pm(13−)
143Pm6182142.9109381(32)265(7) dEC143Nd5/2+
β+ (<5.7×10−6%)
144Pm6183143.9125962(31)363(14) dEC144Nd5−
β+ (<8×10−5%)
144m1Pm840.90(5) keV780(200) nsIT144Pm(9)+
144m2Pm8595.8(22) keV~2.7 μsIT144Pm(27+)
145Pm6184144.9127557(30)17.7(4) yEC145Nd5/2+
α (2.8×10−7%)141Pr
146Pm6185145.9147022(46)5.53(5) yEC (66.0%) [2] 146Nd3−
β (34.0%)146Sm
147Pm [n 10] 6186146.9151449(14)2.6234(2) yβ147Sm7/2+Trace [n 11]
148Pm6187147.9174811(61)5.368(7) dβ148Sm1−
148mPm137.9(3) keV41.29(11) dβ (95.8%)148Sm5−, 6−
IT (4.2%)148Pm
149Pm [n 10] 6188148.9183415(23)53.08(5) hβ149Sm7/2+
149mPm240.214(7) keV35(3) μsIT149Pm11/2−
150Pm6189149.920990(22)2.698(15) hβ150Sm(1−)
151Pm [n 10] 6190150.9212166(49)28.40(4) hβ151Sm5/2+
152Pm6191151.923505(28)4.12(8) minβ152Sm1+
152mPm140(90) keV [n 9] 7.52(8) minβ152Sm4(−)
153Pm6192152.9241563(97)5.25(2) minβ153Sm5/2−
154Pm6193153.926713(27)2.68(7) minβ154Sm(4+)
154mPm [n 9] −230(50) keV1.73(10) minβ154Sm(1−)
155Pm6194154.9281370(51)41.5(2) sβ155Sm(5/2−)
156Pm6195155.9311141(13)27.4(5) sβ156Sm4+
156mPm150.30(10) keV2.3(20) sIT (98%)156Pm1+#
β (2%)156Sm
157Pm6196156.9331213(75)10.56(10) sβ157Sm(5/2−)
158Pm6197157.93654695(95)4.8(5) sβ158Sm(0+,1+)#
158mPm150(50)# keV>16 μsIT158Pm5+#
159Pm6198158.939286(11)1.648+0.43
−0.42
 s
[4]
β159Sm(5/2−)
159mPm1465.0(5) keV4.42(17) μsIT159Pm17/2+#
β, n (<0.6%) [4] 158Sm
160Pm6199159.9432153(22)874+16
−12
 ms
[4]
β160Sm6−#
β, n (<0.1%) [4] 159Sm
160mPm191(11) keV>700 ms1−#
161Pm61100160.9462298(97)724+20
−12
 ms
[4]
β (98.91%)161Sm(5/2−)
β, n (1.09%) [4] 160Sm
161mPm965.9(9) keV890(90) nsIT161Pm(13/2+)
162Pm61101161.95057(32)#467+38
−18
 ms
[4]
β (98.21%)162Sm2+#
β, n (1.79%) [4] 161Sm
163Pm61102162.95388(43)#362+42
−30
 ms
[4]
β (95%)163Sm5/2−#
β, n (5.00%) [4] 162Sm
164Pm61103163.95882(43)#280+38
−33
 ms
[4]
β (93.82%)164Sm5−#
β, n (6.18%) [4] 163Sm
165Pm61104164.96278(54)#297+111
−101
 ms
[4]
β (86.74%)165Sm5/2−#
β, n (13.26%) [4] 164Sm
166Pm61105228+131
−112
 ms
[4]
β166Sm
β, n (<52%) [4] 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. 1 2 3 #  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. 1 2 3 4 Order of ground state and isomer is uncertain.
  10. 1 2 3 Fission product
  11. Spontaneous fission product of 232Th, 235U, 238U and 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 all stable with respect to beta decay, so the isotopes of promethium with those masses cannot be produced by beta decay and therefore are not fission products in significant quantities (they could only be produced directly, rather than along a beta-decay chain). 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. [5]

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. [6]

See also

Daughter products other than promethium

References

  1. 1 2 3 4 Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. 1 2 "146Pm ε decay" (PDF). NNDC Chart of Nuclides.
  3. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 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 .
  5. 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.
  6. "Apollo Experience Report - Protection Against Radiation" (PDF). NASA. Archived from the original (PDF) on 14 November 2014. Retrieved 9 December 2011.