Isotopes of promethium

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Promethium (Pm) has no stable isotopes, and does not exist in nature, except in trace quantities as a product of spontaneous fission and alpha decay of 151Eu. It is a synthetic element, first produced in 1945. Thirty-eight 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 atomic weight from 125.95752 u (126Pm) to 162.95368 u (163Pm). The primary decay mode before the longest-lived isotope, 145Pm, is electron capture, and the primary mode after is beta minus decay. The primary decay products before 145Pm are isotopes of neodymium and the primary products after are isotopes of samarium.

Since promethium does not exist in nature, a standard atomic mass cannot be given.

Stability of promethium isotopes[edit]

Promethium is one of the two elements of the first 82 elements that have no stable isotopes; the other is technetium (No. 43). This is a rarely occurring effect of the liquid drop model.

Promethium-147[edit]

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.

Promethium-147 is used as a beta radiation 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. [1]

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[2][n 1]
daughter
isotope(s)[n 2]
nuclear
spin
excitation energy
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+ (.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 β+ 143Nd 5/2+
144Pm 61 83 143.912591(3) 363(14) d β+ 144Nd 5-
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) a EC 145Nd 5/2+
α (2.8×10−7%) 141Pr
146Pm 61 85 145.914696(5) 5.53(5) a EC (66%) 146Nd 3-
β- (34%) 146Sm
147Pm[n 3] 61 86 146.9151385(26) 2.6234(2) a β- 147Sm 7/2+
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 3] 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 3] 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)# 1.47(15) s β- 159Sm 5/2-#
160Pm 61 99 159.94299(32)# 2# s β- 160Sm
161Pm 61 100 160.94586(54)# 700# ms β- 161Sm 5/2-#
162Pm 61 101 161.95029(75)# 500# ms β- 162Sm
163Pm 61 102 162.95368(86)# 200# ms β- 163Sm 5/2-#
  1. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  2. ^ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
  3. ^ a b c Fission product

Notes[edit]

  • Values marked # are not purely derived from experimental data, but at least partly estimated from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References[edit]

  1. ^ "Apollo Experience Report - Protection Against Radiation". NASA. Retrieved 9 December 2011. 
  2. ^ http://www.nucleonica.net/unc.aspx


Isotopes of neodymium Isotopes of promethium Isotopes of samarium
Table of nuclides