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Isotopes of promethium

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Main isotopes^[1]			Decay
Isotope	abundance	half-life(t_1/2)	mode	product
¹⁴³Pm	synth	265 d	ε	¹⁴³Nd
¹⁴⁴Pm	synth	363 d	ε	¹⁴⁴Nd
¹⁴⁵Pm	synth	17.7 y	ε	¹⁴⁵Nd
¹⁴⁵Pm	synth	17.7 y	α	¹⁴¹Pr
¹⁴⁶Pm	synth	5.53 y	ε	¹⁴⁶Nd
¹⁴⁶Pm	synth	5.53 y	β⁻	¹⁴⁶Sm
¹⁴⁷Pm	trace	2.6234 y	β⁻	¹⁴⁷Sm

Promethium (₆₁Pm) is anartificial element, except in trace quantities as a product ofspontaneous fission of²³⁸U and²³⁵U and alpha decay of¹⁵¹Eu, and thus astandard atomic weight cannot be given. Like all artificial elements, it has nostable isotopes. It was first synthesized in 1945.

The known isotopes run from¹²⁸Pm to¹⁶⁶Pm, 39 in all; the most stable are¹⁴⁵Pm with ahalf-life of 17.7 years,¹⁴⁶Pm with a half-life of 5.53 years, and¹⁴⁷Pm (the common isotope) with a half-life of 2.6234 years.¹⁴³Pm and¹⁴⁴Pm 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 knownmeta states with the most stable being^148mPm at a half-life of 41.29 days.

The primarydecay mode for isotopes lighter than¹⁴⁶Pm iselectron capture resulting inisotopes of neodymium, and the primary decay mode heavier than¹⁴⁶Pm isbeta decay givingisotopes of samarium; promethium-146 itself decays both ways.

List of isotopes

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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
Nuclide ^{[n 1]}	Excitation energy^{[n 4]}			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
¹²⁸Pm	61	67	127.94823(32)#	1.0(3) s	β⁺ (?%)	¹²⁸Nd	4+#
¹²⁸Pm	61	67	127.94823(32)#	1.0(3) s	β⁺,p (?%)	¹²⁷Pr	4+#
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+)
¹³⁰Pm	61	69	129.94045(22)#	2.6(2) s	β⁺, p (?%)	¹²⁹Pr	(5+, 6+, 4+)
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+)
¹³²Pm	61	71	131.93384(16)#	6.2(6) s	β⁺, p (5×10⁻⁵%)	¹³¹Pr	(3+)
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+
¹⁴²Pm	61	81	141.912891(25)	40.5(5) s	EC (22.9%)	¹⁴²Nd	1+
^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+
¹⁴³Pm	61	82	142.9109381(32)	265(7) d	β⁺ (<5.7×10⁻⁶%)	¹⁴³Nd	5/2+
¹⁴⁴Pm	61	83	143.9125962(31)	363(14) d	EC	¹⁴⁴Nd	5−
¹⁴⁴Pm	61	83	143.9125962(31)	363(14) d	β⁺ (<8×10⁻⁵%)	¹⁴⁴Nd	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+
¹⁴⁵Pm	61	84	144.9127557(30)	17.7(4) y	α (2.8×10⁻⁷%)	¹⁴¹Pr	5/2+
¹⁴⁶Pm	61	85	145.9147022(46)	5.53(5) y	EC (66.0%)	¹⁴⁶Nd	3−
¹⁴⁶Pm	61	85	145.9147022(46)	5.53(5) y	β⁻ (34.0%)	¹⁴⁶Sm	3−
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−
^148mPm	137.9(3) keV			41.29(11) d	IT (4.2%)	¹⁴⁸Pm	5−, 6−
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+#
^156mPm	150.30(10) keV			2.3(20) s	β⁻ (2%)	¹⁵⁶Sm	1+#
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+#
^159mPm	1465.0(5) keV			4.42(17) μs	β⁻, n (<0.6%)^[3]	¹⁵⁸Sm	17/2+#
¹⁶⁰Pm	61	99	159.9432153(22)	874+16 −12 ms^[3]	β⁻	¹⁶⁰Sm	6−#
¹⁶⁰Pm	61	99	159.9432153(22)	874+16 −12 ms^[3]	β⁻, n (<0.1%)^[3]	¹⁵⁹Sm	6−#
^160mPm	191(11) keV			>700 ms			1−#
¹⁶¹Pm	61	100	160.9462298(97)	724+20 −12 ms^[3]	β⁻ (98.91%)	¹⁶¹Sm	(5/2−)
¹⁶¹Pm	61	100	160.9462298(97)	724+20 −12 ms^[3]	β⁻, n (1.09%)^[3]	¹⁶⁰Sm	(5/2−)
^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+#
¹⁶²Pm	61	101	161.95057(32)#	467+38 −18 ms^[3]	β⁻, n (1.79%)^[3]	¹⁶¹Sm	2+#
¹⁶³Pm	61	102	162.95388(43)#	362+42 −30 ms^[3]	β⁻ (95%)	¹⁶³Sm	5/2−#
¹⁶³Pm	61	102	162.95388(43)#	362+42 −30 ms^[3]	β⁻, n (5.00%)^[3]	¹⁶²Sm	5/2−#
¹⁶⁴Pm	61	103	163.95882(43)#	280+38 −33 ms^[3]	β⁻ (93.82%)	¹⁶⁴Sm	5−#
¹⁶⁴Pm	61	103	163.95882(43)#	280+38 −33 ms^[3]	β⁻, n (6.18%)^[3]	¹⁶³Sm	5−#
¹⁶⁵Pm	61	104	164.96278(54)#	297+111 −101 ms^[3]	β⁻ (86.74%)	¹⁶⁵Sm	5/2−#
¹⁶⁵Pm	61	104	164.96278(54)#	297+111 −101 ms^[3]	β⁻, n (13.26%)^[3]	¹⁶⁴Sm	5/2−#
¹⁶⁶Pm	61	105		228+131 −112 ms^[3]	β⁻	¹⁶⁶Sm
¹⁶⁶Pm	61	105		228+131 −112 ms^[3]	β⁻, n (<52%)^[3]	¹⁶⁵Sm
This table header & footer: view

^^mPm – Excitednuclear isomer.
^( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^^a ^b ^c# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^Modes of decay:
EC: Electron capture

IT: Isomeric transition
n: Neutron emission
p: Proton emission
^Bold italics symbol as daughter – Daughter product is nearly stable.
^Bold symbol as daughter – Daughter product is stable.
^( ) spin value – Indicates spin with weak assignment arguments.
^^a ^b ^c ^dOrder of ground state and isomer is uncertain.
^^a ^b ^cFission product
^Spontaneous fission product of²³²Th,²³⁵U,²³⁸U andalpha decay daughter of primordial¹⁵¹Eu

Stability of promethium isotopes

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Promethium is one of the two elements of the first 82 elements that has no stable isotopes. This is a rarely occurring effect of theliquid drop model. Namely, promethium does not have anybeta-stable isotopes, as for anymass number, it is energetically favorable for a promethium isotope to undergopositron emission orbeta decay, respectively forming a neodymium or samarium isotope which has a higherbinding energy per nucleon. The other element for which this happens istechnetium (Z = 43).

Promethium-147

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Promethium-147beta decays to the long-livedprimordial radioisotope samarium-147 with a half-life of 2.6234 years, emitting low-energy beta radiation without gamma emission. It is a commonfission product, produced innuclear reactors and in trace quantities in nature, where it is also produced by thealpha decay of europium-151.^[4]

In the reactor environment, it is almost exclusively produced through beta decay ofneodymium-147 as usual for fission products. The isotopes^142-146Nd,¹⁴⁸Nd, and¹⁵⁰Nd are allstable 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 and¹⁵¹Pm are, but have half-lives of only 53.08 and 28.40 hours, so are not found inspent nuclear fuel that has been cooled for months or years.

Promethium-147 is used as abeta particle source and aradioisotope thermoelectric generator (RTG) fuel; its power density is about 2 watts per gram. Mixed with a phosphor, it was used toilluminate theApollo Lunar Module electrical switch tips and the control panels of theLunar Roving Vehicle.^[5] For luminescent applications, it has generally been replaced bytritium, which is even safer and has a longer half-life (12.32 years).

References

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^^a ^b ^c ^dKondev, 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.
^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.
^^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^pKiss, 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.
^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.
^"Apollo Experience Report - Protection Against Radiation"(PDF). NASA. Archived fromthe original(PDF) on 14 November 2014. Retrieved9 December 2011.

Isotopes of thechemical elements

Group	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
Period	Hydrogen and alkali metals	Alkaline earth metals													Pnictogens	Chalcogens	Halogens	Noble gases
①	Isotopes § List H 1																	Isotopes § List He 2
②	Isotopes § List Li 3	Isotopes § List Be 4											Isotopes § List B 5	Isotopes § List C 6	Isotopes § List N 7	Isotopes § List O 8	Isotopes § List F 9	Isotopes § List Ne 10
③	Isotopes § List Na 11	Isotopes § List Mg 12											Isotopes § List Al 13	Isotopes § List Si 14	Isotopes § List P 15	Isotopes § List S 16	Isotopes § List Cl 17	Isotopes § List Ar 18
④	Isotopes § List K 19	Isotopes § List Ca 20	Isotopes § List Sc 21	Isotopes § List Ti 22	Isotopes § List V 23	Isotopes § List Cr 24	Isotopes § List Mn 25	Isotopes § List Fe 26	Isotopes § List Co 27	Isotopes § List Ni 28	Isotopes § List Cu 29	Isotopes § List Zn 30	Isotopes § List Ga 31	Isotopes § List Ge 32	Isotopes § List As 33	Isotopes § List Se 34	Isotopes § List Br 35	Isotopes § List Kr 36
⑤	Isotopes § List Rb 37	Isotopes § List Sr 38	Isotopes § List Y 39	Isotopes § List Zr 40	Isotopes § List Nb 41	Isotopes § List Mo 42	Isotopes § List Tc 43	Isotopes § List Ru 44	Isotopes § List Rh 45	Isotopes § List Pd 46	Isotopes § List Ag 47	Isotopes § List Cd 48	Isotopes § List In 49	Isotopes § List Sn 50	Isotopes § List Sb 51	Isotopes § List Te 52	Isotopes § List I 53	Isotopes § List Xe 54
⑥	Isotopes § List Cs 55	Isotopes § List Ba 56	Isotopes § List Lu 71	Isotopes § List Hf 72	Isotopes § List Ta 73	Isotopes § List W 74	Isotopes § List Re 75	Isotopes § List Os 76	Isotopes § List Ir 77	Isotopes § List Pt 78	Isotopes § List Au 79	Isotopes § List Hg 80	Isotopes § List Tl 81	Isotopes § List Pb 82	Isotopes § List Bi 83	Isotopes § List Po 84	Isotopes § List At 85	Isotopes § List Rn 86
⑦	Isotopes § List Fr 87	Isotopes § List Ra 88	Isotopes § List Lr 103	Isotopes § List Rf 104	Isotopes § List Db 105	Isotopes § List Sg 106	Isotopes § List Bh 107	Isotopes § List Hs 108	Isotopes § List Mt 109	Isotopes § List Ds 110	Isotopes § List Rg 111	Isotopes § List Cn 112	Isotopes § List Nh 113	Isotopes § List Fl 114	Isotopes § List Mc 115	Isotopes § List Lv 116	Isotopes § List Ts 117	Isotopes § List Og 118
⑧	Isotopes § List Uue 119	Isotopes § List Ubn 120

			Isotopes § List La 57	Isotopes § List Ce 58	Isotopes § List Pr 59	Isotopes § List Nd 60	Isotopes § List Pm 61	Isotopes § List Sm 62	Isotopes § List Eu 63	Isotopes § List Gd 64	Isotopes § List Tb 65	Isotopes § List Dy 66	Isotopes § List Ho 67	Isotopes § List Er 68	Isotopes § List Tm 69	Isotopes § List Yb 70
			Isotopes § List Ac 89	Isotopes § List Th 90	Isotopes § List Pa 91	Isotopes § List U 92	Isotopes § List Np 93	Isotopes § List Pu 94	Isotopes § List Am 95	Isotopes § List Cm 96	Isotopes § List Bk 97	Isotopes § List Cf 98	Isotopes § List Es 99	Isotopes § List Fm 100	Isotopes § List Md 101	Isotopes § List No 102