Isotopes of promethium

Isotopes of promethium (₆₁Pm)
α	141Pr
β−	146Sm
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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.

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 (t_1/2 41.29 days), ^152m2Pm (t_1/2 13.8 minutes) and ^152mPm (t_1/2 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 decay. The primary decay products before ¹⁴⁵Pm are isotopes of neodymium and the primary products after are isotopes of samarium.

Stability of promethium isotopes

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

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.

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.^[2]

List of isotopes

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)^[3]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin and parity
nuclide symbol	excitation energy			half-life	decay mode(s)^[3]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin and parity
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+#
¹²⁸Pm	61	67	127.94842(43)#	1.0(3) s	p	¹²⁷Nd	6+#
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+)
¹³⁰Pm	61	69	129.94045(32)#	2.6(2) s	β⁺, p (rare)	¹²⁹Pr	(5+,6+,4+)
¹³¹Pm	61	70	130.93587(21)#	6.3(8) s	β⁺, p	¹³⁰Pr	5/2+#
¹³¹Pm	61	70	130.93587(21)#	6.3(8) s	β⁺	¹³¹Nd	5/2+#
¹³²Pm	61	71	131.93375(21)#	6.2(6) s	β⁺	¹³²Nd	(3+)
¹³²Pm	61	71	131.93375(21)#	6.2(6) s	β⁺, p (5×10⁻⁵%)	¹³¹Pr	(3+)
¹³³Pm	61	72	132.92978(5)	15(3) s	β⁺	¹³³Nd	(3/2+)
^133mPm	130.4(10) keV			10# s	β⁺	¹³³Nd	(11/2−)
^133mPm	130.4(10) keV			10# s	IT	¹³³Pm	(11/2−)
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)−
^139mPm	188.7(3) keV			180(20) ms	β⁺ (0.17%)	¹³⁹Nd	(11/2)−
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) y	EC	¹⁴⁵Nd	5/2+
¹⁴⁵Pm	61	84	144.912749(3)	17.7(4) y	α (2.8×10⁻⁷%)	¹⁴¹Pr	5/2+
¹⁴⁶Pm	61	85	145.914696(5)	5.53(5) y	EC (66%)	¹⁴⁶Nd	3−
¹⁴⁶Pm	61	85	145.914696(5)	5.53(5) y	β⁻ (34%)	¹⁴⁶Sm	3−
¹⁴⁷Pm^{[n 3]}	61	86	146.9151385(26)	2.6234(2) y	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−
^148mPm	137.9(3) keV			41.29(11) d	IT (5%)	¹⁴⁸Pm	5−,6−
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−#

^ Abbreviations:
EC: Electron capture
IT: Isomeric transition
^ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
^ ^a ^b ^c Fission product

Notes

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

^ 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.
^ "Apollo Experience Report - Protection Against Radiation" (PDF). NASA. Retrieved 9 December 2011.
^ "Universal Nuclide Chart". nucleonica. {{cite web}}: Unknown parameter |registration= ignored (|url-access= suggested) (help)

Isotope masses from:
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. {{cite journal}}: Unknown parameter |laysummary= ignored (help)
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. {{cite web}}: Check date values in: |accessdate= (help)
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide (ed.). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9. {{cite book}}: Unknown parameter |nopp= ignored (|no-pp= suggested) (help)

[4] Abbreviations:
EC: Electron capture
IT: Isomeric transition

[5] Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)

[FP-6] Fission product

[NUBASE2020-1] 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] "Apollo Experience Report - Protection Against Radiation" (PDF). NASA. Retrieved 9 December 2011.

[3] "Universal Nuclide Chart". nucleonica. {{cite web}}: Unknown parameter |registration= ignored (|url-access= suggested) (help)

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