Isotopes of promethium

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.

Main isotopes of promethium (₆₁Pm)

Iso­tope Decay 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

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 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) [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
	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	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+
					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)#	1.47(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. ^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. # – 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
   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. 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 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.[1]

References

1. "Apollo Experience Report - Protection Against Radiation" (PDF). NASA. Archived from the original (PDF) on 14 November 2014. Retrieved 9 December 2011.

• 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, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • 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. Lay summary.
• 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, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.