Isotopes of praseodymium

Isotopes of praseodymium (₅₉Pr)
ε	142Ce
Standard atomic weight Ar°(Pr)
	140.90766±0.00001; 140.91±0.01 (abridged);

Naturally occurring praseodymium (₅₉Pr) is composed of one stable isotope, ¹⁴¹Pr. Forty radioisotopes have been characterized with the most stable being ¹⁴³Pr, with a half-life of 13.57 days and ¹⁴²Pr, with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than six hours and the majority of these have half-lives that are less than 33 seconds. This element also has 19 meta states with the most stable being ^138mPr (2.12 hours), ^142mPr (14.6 minutes) and ^134mPr (~11 minutes).

The known isotopes of praseodymium range from ¹²¹Pr to ¹⁶¹Pr. The primary decay mode of isotopes lighter than ¹⁴¹Pr is positron emission or electron capture to isotopes of cerium, while that of heavier isotopes is beta decay to isotopes of neodymium.

List of isotopes

Nuclide ^{[n 1]}	Z	N	Isotopic mass (Da)^[4] ^{[n 2]}^{[n 3]}	Discovery year^[5]^[6]	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]}			Discovery year^[5]^[6]	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
¹²¹Pr	59	62	120.95539(54)#	2005	12(5) ms	p	¹²⁰Ce	(3/2)(+#)
¹²²Pr^[7]	59	63	121.95193(54)#	2025	500# ms [>310 ns]
¹²³Pr^[7]	59	64	122.94608(43)#	2025	800# ms [>310 ns]			3/2+#
¹²⁴Pr	59	65	123.94294(43)#	1986	1.2(2) s	β⁺	¹²⁴Ce
¹²⁴Pr	59	65	123.94294(43)#	1986	1.2(2) s	β⁺, p (?%)	¹²³La
¹²⁵Pr	59	66	124.93766(32)#	2002	3.3(7) s	β⁺	¹²⁵Ce	3/2+#
¹²⁶Pr	59	67	125.93524(21)#	1983	3.12(18) s	β⁺	¹²⁶Ce	(4, 5)
¹²⁶Pr	59	67	125.93524(21)#	1983	3.12(18) s	β⁺, p (?%)	¹²⁵La	(4, 5)
¹²⁷Pr	59	68	126.93071(21)#	1995	4.2(3) s	β⁺	¹²⁷Ce	3/2+#
^127mPr	600(200)# keV			(1998)^{[n 9]}	2# μs			(11/2−)
¹²⁸Pr	59	69	127.928791(32)	1985	2.85(9) s	β⁺	¹²⁸Ce	(3+)
¹²⁸Pr	59	69	127.928791(32)	1985	2.85(9) s	β⁺, p (?%)	¹²⁷La	(3+)
¹²⁹Pr	59	70	128.925095(32)	1977	30(4) s	β⁺	¹²⁹Ce	(3/2+)
^129mPr	382.57(24) keV			(1997)^{[n 9]}	26(11)# μs	IT	¹²⁹Pr	(11/2−)
¹³⁰Pr	59	71	129.923590(69)	1977	40.0(4) s	β⁺	¹³⁰Ce	(6, 7)(+#)
^130mPr	100(100)# keV			(1990)^{[n 10]}	10# s			2+#
¹³¹Pr	59	72	130.920235(50)	1977	1.50(3) min	β⁺	¹³¹Ce	(3/2+)
^131mPr	152.4(3) keV			1996	5.73(20) s	IT (96.4%)	¹³¹Pr	(11/2−)
^131mPr	152.4(3) keV			1996	5.73(20) s	β⁺ (3.6%)	¹³¹Ce	(11/2−)
¹³²Pr	59	73	131.919240(31)	1974	1.49(11) min	β⁺	¹³²Ce	(2+)
^132m1Pr^{[n 11]}	30(30)# keV			(1990)^{[n 9]}	1# s			(5+)
^132m2Pr	250(30)# keV			2012	2.46(4) μs	IT	¹³²Pr	(8+)
^132m3Pr	300(30)# keV			2012	486(70) ns	IT	¹³²Pr	(8−)
¹³³Pr	59	74	132.916331(13)	1970	6.5(3) min	β⁺	¹³³Ce	5/2+
^133mPr	192.12(14) keV			2001	1.1(2) μs	IT	¹³³Pr	(11/2−)
¹³⁴Pr	59	75	133.915697(22)	1967	17(2) min	β⁺	¹³⁴Ce	2−
^134mPr	67.7(4) keV			1973	~11 min	β⁺	¹³⁴Ce	6−
¹³⁵Pr	59	76	134.913112(13)	1954	24(1) min	β⁺	¹³⁵Ce	3/2+
^135mPr	358.06(6) keV			1973	105(10) μs	IT	¹³⁵Pr	(11/2−)
¹³⁶Pr	59	77	135.912677(12)	1968	13.1(1) min	β⁺	¹³⁶Ce	2+
¹³⁷Pr	59	78	136.9106792(87)	1958	1.28(3) h	β⁺	¹³⁷Ce	5/2+
^137mPr	561.22(23) keV			1975	2.66(7) μs	IT	¹³⁷Pr	11/2−
¹³⁸Pr	59	79	137.910757(11)	1951	1.45(5) min	β⁺	¹³⁸Ce	1+
^138mPr	350(19) keV			1966	2.12(4) h	β⁺	¹³⁸Ce	7−
¹³⁹Pr	59	80	138.9089327(39)	1951	4.41(4) h	β⁺	¹³⁹Ce	5/2+
¹⁴⁰Pr	59	81	139.9090856(66)	1938	3.39(1) min	EC (51.3%)	¹⁴⁰Ce	1+
¹⁴⁰Pr	59	81	139.9090856(66)	1938	3.39(1) min	β⁺ (48.7%)	¹⁴⁰Ce	1+
^140m1Pr	127.8(3) keV			1964	0.35(2) μs	IT	¹⁴⁰Pr	5+
^140m2Pr	763.7(5) keV			1964	3.05(20) μs	IT	¹⁴⁰Pr	(7)−
¹⁴¹Pr^{[n 12]}	59	82	140.9076596(16)	1924	Stable			5/2+	1.0000
¹⁴²Pr	59	83	141.9100516(16)	1935	19.12(4) h	β⁻ (99.98%)	¹⁴²Nd	2−
¹⁴²Pr	59	83	141.9100516(16)	1935	19.12(4) h	EC (0.0164%)	¹⁴²Ce	2−
^142mPr	3.694(3) keV			1967	14.6(5) min	IT	¹⁴²Pr	5−
¹⁴³Pr^{[n 12]}	59	84	142.9108226(19)	1951	13.57(2) d	β⁻	¹⁴³Nd	7/2+
¹⁴⁴Pr^{[n 12]}	59	85	143.9133107(29)	1946	17.28(5) min	β⁻	¹⁴⁴Nd	0−
^144mPr^{[n 12]}	59.03(3) keV			1970	7.2(3) min	IT (~99.93%)	¹⁴⁴Pr	3−
^144mPr^{[n 12]}	59.03(3) keV			1970	7.2(3) min	β⁻ (~0.07%)	¹⁴⁴Nd	3−
¹⁴⁵Pr	59	86	144.9145180(77)	1954	5.984(10) h	β⁻	¹⁴⁵Nd	7/2+
¹⁴⁶Pr	59	87	145.917688(37)	1953	24.09(10) min	β⁻	¹⁴⁶Nd	(2−)
¹⁴⁷Pr	59	88	146.919007(17)	1964	13.39(4) min	β⁻	¹⁴⁷Nd	3/2+
¹⁴⁸Pr	59	89	147.922130(16)	1964	2.29(2) min	β⁻	¹⁴⁸Nd	1−
^148mPr	76.80(20) keV			1979	2.01(7) min	β⁻ (64%)	¹⁴⁸Nd	(4)
^148mPr	76.80(20) keV			1979	2.01(7) min	IT (36%)	¹⁴⁸Pr	(4)
¹⁴⁹Pr	59	90	148.923736(11)	1964	2.26(7) min	β⁻	¹⁴⁹Nd	(5/2+)
¹⁵⁰Pr	59	91	149.9266764(97)	1970	6.19(16) s	β⁻	¹⁵⁰Nd	1−
¹⁵¹Pr	59	92	150.928309(13)	1990	18.90(7) s	β⁻	¹⁵¹Nd	(3/2−)
^151mPr	35.10(10) keV			2006	50(8) μs	IT	¹⁵¹Pr	(7/2+)
¹⁵²Pr	59	93	151.931553(20)	1983	3.57(11) s	β⁻	¹⁵²Nd	4+
^152mPr	115.1(3) keV			1990	4.16(10) μs	IT	¹⁵²Pr	(1+)
¹⁵³Pr	59	94	152.933904(13)	1987	4.28(11) s	β⁻	¹⁵³Nd	3/2−#
¹⁵⁴Pr	59	95	153.93789(11)	1988	2.30(9) s	β⁻	¹⁵⁴Nd	(3+)
¹⁵⁵Pr	59	96	154.940509(18)	2012	1.47(3) s	β⁻	¹⁵⁵Nd	3/2−#
¹⁵⁶Pr	59	97	155.9447669(11)	2017	444(6) ms	β⁻	¹⁵⁶Nd	1+#
¹⁵⁷Pr	59	98	156.9480031(34)	2017	307(21) ms	β⁻	¹⁵⁷Nd	3/2−#
¹⁵⁸Pr	59	99	157.95260(32)#	2017	181(14) ms	β⁻	¹⁵⁸Nd	5−#
¹⁵⁹Pr	59	100	158.95623(43)#	2017	134(43) ms	β⁻	¹⁵⁹Nd	3/2−#
¹⁶⁰Pr	59	101	159.96114(43)#	2017	170(140) ms	β⁻	¹⁶⁰Nd	1+#
¹⁶¹Pr	59	102	160.96512(54)#	2018	90# ms [>550 ns]			3/2−#
This table header & footer:

^ ^mPr – Excited nuclear 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

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 Half-life not measured, not included in discovery database
^ Only published in a conference proceeding and not a refereed journal.
^ Order of ground state and isomer is uncertain.
^ ^a ^b ^c ^d Fission product

References

^ ^a ^b ^c ^d 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.
^ "Standard Atomic Weights: Praseodymium". CIAAW. 2017.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ 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.
^ FRIB Nuclear Data Group. "Discovery of Nuclides Project, Isotope Database". doi:10.11578/frib/2279152.
^ FRIB Nuclear Data Group. "Discovery of Nuclides Project, Isomer Database". doi:10.11578/frib/2572219.
^ ^a ^b Suzuki, H; Fukuda, N; Takeda, H; Shimizu, Y; Yoshimoto, M; Togano, Y; Sato, H; Kitamura, N; Hanai, S; Momota, S; Kusaka, K; Yanagisawa, Y; Ohtake, M; Sumikama, T; Fukunishi, N; Michimasa, S (7 November 2025). "Discovery of Proton-Rich Radioactive Isotopes in the Z = 60 Region Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 238U Beam". Progress of Theoretical and Experimental Physics. 2025 (11). doi:10.1093/ptep/ptaf149.

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
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 3.0 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.

[4] Pr – Excited nuclear isomer.

[6] ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

[TMS-7] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[TNN-10] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[11] Modes of decay:

EC: Electron capture

IT: Isomeric transition

p: Proton emission

[12] Bold italics symbol as daughter – Daughter product is nearly stable.

[13] Bold symbol as daughter – Daughter product is stable.

[14] ( ) spin value – Indicates spin with weak assignment arguments.

[notm-16] Half-life not measured, not included in discovery database

[17] Only published in a conference proceeding and not a refereed journal.

[order-18] Order of ground state and isomer is uncertain.

[FP-19] 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.

[CIAAWpraseodymium-2] "Standard Atomic Weights: Praseodymium". CIAAW. 2017.

[CIAAW2021-3] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[AME2020_II-5] 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.

[IsotopeFRIB-8] FRIB Nuclear Data Group. "Discovery of Nuclides Project, Isotope Database". doi:10.11578/frib/2279152.

[IsomerFRIB-9] FRIB Nuclear Data Group. "Discovery of Nuclides Project, Isomer Database". doi:10.11578/frib/2572219.

[suzuki2025-15] Suzuki, H; Fukuda, N; Takeda, H; Shimizu, Y; Yoshimoto, M; Togano, Y; Sato, H; Kitamura, N; Hanai, S; Momota, S; Kusaka, K; Yanagisawa, Y; Ohtake, M; Sumikama, T; Fukunishi, N; Michimasa, S (7 November 2025). "Discovery of Proton-Rich Radioactive Isotopes in the Z = 60 Region Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 238U Beam". Progress of Theoretical and Experimental Physics. 2025 (11). doi:10.1093/ptep/ptaf149.

[1]

[2]

[3]

[n 1]

[4]

[n 2]

[n 3]

[5]

[6]

[n 4]

[n 5]

[n 6]

[n 7]

[n 8]

[7]

[n 9]

[n 10]

[n 11]

[n 12]

EC:	Electron capture
IT:	Isomeric transition
p:	Proton emission

List of isotopes

See also

References