Isotopes of terbium

Isotopes of terbium (₆₅Tb)
β−	158Dy
Standard atomic weight Ar°(Tb)
	158.925354±0.000007; 158.93±0.01 (abridged);

Naturally occurring terbium (₆₅Tb) is composed of one stable isotope, ¹⁵⁹Tb. Thirty-seven radioisotopes have been characterized, with the most stable being ¹⁵⁸Tb with a half-life of 180 years, ¹⁵⁷Tb with a half-life of 71 years, and ¹⁶⁰Tb with a half-life of 72.3 days. All of the remaining radioactive isotopes have half-lives that are less than one week, and the majority of these have half-lives that are less than 24 seconds. This element also has 27 meta states, with the most stable being ^156m2Tb (t_1/2 = 24.4 hours), ^154m2Tb (t_1/2 = 22.7 hours) and ^154m1Tb (t_1/2 = 21.5 hours).

The primary decay mode before the most abundant stable isotope, ¹⁵⁹Tb, is electron capture to gadolinium isotopes, and the primary mode after is beta decay to dysprosium isotopes.

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
¹³⁵Tb	65	70	134.96452(43)#	2004	1.01(28) ms	p	¹³⁴Gd	(7/2−)
¹³⁶Tb^[7]	65	71	135.96146(54)#	2026	200# ms [>310 ns]			5−#
¹³⁷Tb^[7]	65	72	136.95602(43)#	2026	600# ms [>310 ns]			3/2+#
¹³⁸Tb^[7]	65	73	137.95319(32)#	2026	800# ms [>310 ns]			2+#
¹³⁹Tb	65	74	138.94833(32)#	1999	1.6(2) s	β⁺	¹³⁹Gd	5/2−#
¹⁴⁰Tb	65	75	139.94581(86)	1986	2.29(15) s	β⁺ (99.74%)	¹⁴⁰Gd	(7+)
						EC (<3%)	¹⁴⁰Gd
						β⁺, p (0.26%)	¹³⁹Eu
¹⁴¹Tb	65	76	140.94145(11)	1986	3.5(2) s	β⁺	¹⁴¹Gd	(5/2−)
^141mTb^{[n 9]}^{[n 10]}	0(200)# keV			(1988)^{[n 11]}	7.9(6) s	β⁺	¹⁴¹Gd	11/2−#
¹⁴²Tb	65	77	141.93928(75)	1991	597(17) ms	β⁺ (96.8%)	¹⁴²Gd	1+
						EC (3.2%)	¹⁴²Gd
						β⁺, p (0.0022%)	¹⁴¹Eu
^142m1Tb	279.7(4) keV			1991	303(17) ms	IT	¹⁴²Tb	5−
^142m2Tb	652.1(6) keV			2009	26(1) μs	IT	¹⁴²Tb	8+
¹⁴³Tb	65	78	142.935137(55)	1985	12(1) s	β⁺	¹⁴³Gd	(11/2−)
^143mTb^{[n 9]}	0(100)# keV			(1986)^{[n 12]}	17(4) s			5/2+#
¹⁴⁴Tb	65	79	143.933045(30)	1982	~1 s	β⁺	¹⁴⁴Gd	1+
^144m1Tb	396.9(5) keV			1982	4.25(15) s	IT (66%)	¹⁴⁴Tb	6−
^144m1Tb	396.9(5) keV			1982	4.25(15) s	β⁺ (34%)	¹⁴⁴Gd	6−
^144m2Tb	476.2(5) keV			1996	2.8(3) μs	IT	¹⁴⁴Tb	(8−)
^144m3Tb	517.1(5) keV			1996	670(60) ns	IT	¹⁴⁴Tb	(9+)
^144m4Tb	544.5(6) keV			(1996)^{[n 12]}	<300 ns	IT	¹⁴⁴Tb	(10+)
¹⁴⁵Tb	65	80	144.92872(12)	1981	30.9(6) s	β⁺	¹⁴⁵Gd	(11/2−)
^145mTb^{[n 9]}	860(230) keV			1993				(3/2+)
¹⁴⁶Tb	65	81	145.927253(48)	1974	8(4) s	β⁺	¹⁴⁶Gd	1+
^146m1Tb^{[n 9]}	150(100)# keV			1982	24.1(5) s	β⁺	¹⁴⁶Gd	5−
^146m2Tb	930(100)# keV			1984	1.18(2) ms	IT	¹⁴⁶Tb	10+
¹⁴⁷Tb	65	82	146.9240546(87)	1969	1.64(3) h	β⁺	¹⁴⁷Gd	(1/2+)
^147mTb	50.6(9) keV			1969	1.87(5) min	β⁺	¹⁴⁷Gd	(11/2−)
¹⁴⁸Tb	65	83	147.924275(13)	1960	60(1) min	β⁺	¹⁴⁸Gd	2−
^148m1Tb	90.1(3) keV			1973	2.20(5) min	β⁺	¹⁴⁸Gd	(9)+
^148m2Tb	8618.6(10) keV			1980	1.310(7) μs	IT	¹⁴⁸Tb	(27+)
¹⁴⁹Tb	65	84	148.9232538(39)	1950	4.118(25) h	β⁺ (83.3%)	¹⁴⁹Gd	1/2+
¹⁴⁹Tb	65	84	148.9232538(39)	1950	4.118(25) h	α (16.7%)	¹⁴⁵Eu	1/2+
^149mTb	35.78(13) keV			1962	4.16(4) min	β⁺ (99.98%)	¹⁴⁹Gd	11/2−
^149mTb	35.78(13) keV			1962	4.16(4) min	α (0.022%)	¹⁴⁵Eu	11/2−
¹⁵⁰Tb	65	85	149.9236648(79)	1959	3.48(16) h	β⁺	¹⁵⁰Gd	(2)−
^150mTb	461(27) keV			1972	5.8(2) min	β⁺	¹⁵⁰Gd	9+
¹⁵¹Tb	65	86	150.9231090(44)	1953	17.609(1) h	β⁺ (99.99%)	¹⁵¹Gd	1/2+
¹⁵¹Tb	65	86	150.9231090(44)	1953	17.609(1) h	α (0.0095%)	¹⁴⁷Eu	1/2+
^151mTb	99.53(5) keV			1978	25(3) s	IT (93.4%)	¹⁵¹Tb	11/2−
^151mTb	99.53(5) keV			1978	25(3) s	β⁺ (6.6%)	¹⁵¹Gd	11/2−
¹⁵²Tb	65	87	151.924082(43)	1959	17.8784(95) h^[8]	EC (83%)^[8]	¹⁵²Gd	2−
						β⁺ (17%)^[8]	¹⁵²Gd
						α (<7×10⁻⁷%)^[9]	¹⁴⁸Eu
^152m1Tb	342.15(16) keV			1980	960(10) ns	IT	¹⁵²Tb	5−
^152m2Tb	501.74(19) keV			1959	4.2(1) min	IT (78.9%)	¹⁵²Tb	8+
^152m2Tb	501.74(19) keV			1959	4.2(1) min	β⁺ (21.1%)	¹⁵²Gd	8+
¹⁵³Tb	65	88	152.9234417(42)	1957	2.34(1) d	β⁺	¹⁵³Gd	5/2+
^153mTb	163.175(5) keV			1965	186(4) μs	IT	¹⁵³Tb	11/2−
¹⁵⁴Tb	65	89	153.924684(49)	1950	9.994(39) h	β⁺	¹⁵⁴Gd	3−
^154m1Tb^{[n 9]}	130(50)# keV			1955	21.5(4) h	β⁺	¹⁵⁴Gd	0−
^154m2Tb^{[n 9]}	200(150)# keV			1971	22.7(5) h	β⁺	¹⁵⁴Gd	7−
^154m3Tb	405(150)# keV			1982	513(42) ns	IT	¹⁵⁴Tb
¹⁵⁵Tb	65	90	154.923510(11)	1957	5.2346(36) d^[10]	EC	¹⁵⁵Gd	3/2+
¹⁵⁶Tb	65	91	155.9247542(40)	1950	5.35(10) d	β⁺	¹⁵⁶Gd	3−
^156m1Tb	88.4(2) keV			1955	5.3(2) h	IT	¹⁵⁶Tb	(0+)
^156m2Tb	100(50)# keV			1970	24.4(10) h	IT	¹⁵⁶Tb	(7−)
¹⁵⁷Tb	65	92	156.9240319(11)	1960	71(7) y	EC	¹⁵⁷Gd	3/2+
¹⁵⁸Tb	65	93	157.9254199(14)	1957	180(11) y	β⁺ (83.4%)	¹⁵⁸Gd	3−
¹⁵⁸Tb	65	93	157.9254199(14)	1957	180(11) y	β⁻ (16.6%)	¹⁵⁸Dy	3−
^158m1Tb	110.3(12) keV			1957	10.70(17) s	IT	¹⁵⁸Tb	0−
^158m2Tb	388.39(11) keV			1967	0.40(4) ms	IT	¹⁵⁸Tb	7−
¹⁵⁹Tb^{[n 13]}	65	94	158.9253537(12)	1933	Stable			3/2+	1.0000
¹⁶⁰Tb	65	95	159.9271746(12)	1943	72.3(2) d	β⁻	¹⁶⁰Dy	3−
¹⁶¹Tb^{[n 13]}	65	96	160.9275768(13)	1949	6.948(5) d	β⁻	¹⁶¹Dy	3/2+
¹⁶²Tb	65	97	161.9292754(22)	1965	7.60(15) min	β⁻	¹⁶²Dy	(1−)
^162mTb	286(3) keV			2020	10# min			4−#
¹⁶³Tb	65	98	162.9306536(44)	1966	19.5(3) min	β⁻	¹⁶³Dy	3/2+
¹⁶⁴Tb	65	99	163.9333276(20)	1968	3.0(1) min	β⁻	¹⁶⁴Dy	(5+)
^164mTb	145(12) keV			2020	2# min			2+#
¹⁶⁵Tb	65	100	164.9349552(17)	1983	2.11(10) min	β⁻	¹⁶⁵Dy	(3/2+)
^165mTb	207(5) keV			(1986)^{[n 11]}	0.81(8) μs	IT	¹⁶⁵Tb	(7/2−)
¹⁶⁶Tb	65	101	165.9379397(16)	1996	27.1(15) s	β⁻	¹⁶⁶Dy	(1−)
^166mTb	159.0(15) keV			(1986)^{[n 11]}	3.5(4) μs	IT	¹⁶⁶Tb	4−#
¹⁶⁷Tb	65	102	166.9400070(21)	1999	18.9(16) s	β⁻	¹⁶⁷Dy	(3/2+)
^167mTb	200(6) keV			(1986)^{[n 11]}	1.2(1) μs	IT	¹⁶⁷Tb	(7/2−)
¹⁶⁸Tb	65	103	167.9433371(45)	1999	9.4(4) s	β⁻	¹⁶⁸Dy	(4−)
^168mTb	211(1) keV			(1986)^{[n 11]}	0.71(3) μs	IT	¹⁶⁸Tb	(6+)
¹⁶⁹Tb	65	104	168.94581(32)#	2012	5.13(32) s	β⁻	¹⁶⁹Dy	3/2+#
¹⁷⁰Tb	65	105	169.94986(32)#	2012	960(78) ms	β⁻	¹⁷⁰Dy	2−#
¹⁷¹Tb	65	106	170.95301(43)#	2012	1.23(10) s	β⁻	¹⁷¹Dy	3/2+#
¹⁷²Tb	65	107	171.95739(54)#	2012	760(190) ms	β⁻	¹⁷²Dy	6+#
¹⁷³Tb	65	108	172.96081(54)#	2018	400# ms [>550 ns]			3/2+#
¹⁷⁴Tb	65	109	173.96568(54)#	2018	240# ms [>550 ns]			2−#
¹⁷⁵Tb^[11]	65	110		2026
This table header & footer:

^ ^mTb – 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 ^d ^e ^f Order of ground state and isomer is uncertain.
^ Discovery of this isotope is disputed.
^ ^a ^b ^c ^d ^e Only published in a conference proceeding and not a refereed journal
^ ^a ^b Half-life not measured, not included in discovery database
^ ^a ^b 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: Terbium". CIAAW. 2021.
^ 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 ^c Suzuki, H; Fukuda, N; Takeda, H; Shimizu, Y; Yoshimoto, M; Togano, Y; Sato, H; Kitamura, N; Momota, S; Kusaka, K; Yanagisawa, Y; Ohtake, M; Fukunishi, N; Michimasa, S (3 February 2026). "Discovery of Proton-Rich Radioactive Isotopes in the Z = 63–70 Region Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 238U Beam". Progress of Theoretical and Experimental Physics. 2026 (2). doi:10.1093/ptep/ptaf190.
^ ^a ^b ^c Collins, S.M.; Köster, U.; Robinson, A.P.; Ivanov, P.; Cocolios, T.E.; Russell, B.; Fenwick, A.J.; Bernerd, C.; Stegemann, S.; Johnston, K.; Gerami, A.M.; Chrysalidis, K.; Mohamud, H.; Ramirez, N.; Bhaisare, A.; Mewburn-Crook, J.; Cullen, D.M.; Pietras, B.; Pells, S.; Dockx, K.; Stucki, N.; Regan, P.H. (2023). "Determination of the Terbium-152 half-life from mass-separated samples from CERN-ISOLDE and assessment of the radionuclide purity". Applied Radiation and Isotopes. 202 111044. Elsevier BV. Bibcode:2023AppRI.20211044C. doi:10.1016/j.apradiso.2023.111044. ISSN 0969-8043. PMID 37797447.
^ "Adopted Levels for ¹⁵²Tb". NNDC Chart of Nuclides.
^ Collins, S.M.; Robinson, A.P.; Ivanov, P.; Köster, U.; Cocolios, T.E.; Russell, B.; Webster, B.; Fenwick, A.J.; Duchemin, C.; Ramos, J.P.; Chevallay, E.; Jakobsson, U.; Stegemann, S.; Regan, P.H.; Stora, T. (2022). "Half-life determination of 155Tb from mass-separated samples produced at CERN-MEDICIS". Applied Radiation and Isotopes. 190 110480. doi:10.1016/j.apradiso.2022.110480. hdl:10138/350587. PMID 36209648.
^ Sumikama, Toshiyuki; Fukuda, Naoki; Kubo, Toshiyuki; Suzuki, Hiroshi; Takeda, Hiroyuki; Inabe, Naohito; Kameda, Daisuke; Ahn, Deuk Soon; Murai, Daichi; Yoshida, Koichi; Kusaka, Kensuke; Yanagisawa, Yoshiyuki; Ohtake, Masao; Shimizu, Yohei; Sato, Yuki; Sato, Hiromi; Otsu, Hideaki; Baba, Hidetada; Lorusso, Giuseppe; Söderström, Pär-Anders; Isobe, Tadaaki; Imai, Nobuaki; Mukai, Momo; Kimura, Sota; Miyatake, Hiroari; Iwasa, Naohito; Yagi, Ayumi; Yokoyama, Rin; Tarasov, Oleg Borisovich; Geissel, Hans (15 February 2026). "Expanding the Isotopic Frontier: Seven New Neutron-Rich Rare-Earth Isotopes Observed at RIKEN RI Beam Factory". Journal of the Physical Society of Japan. 95 (2). doi:10.7566/JPSJ.95.024202.

[4] Tb – 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.

[order-16] ^ ^a ^b ^c ^d ^e ^f Order of ground state and isomer is uncertain.

[disputed-17] Discovery of this isotope is disputed.

[conf-18] Only published in a conference proceeding and not a refereed journal

[notm-19] Half-life not measured, not included in discovery database

[FP-23] 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.

[CIAAWterbium-2] "Standard Atomic Weights: Terbium". CIAAW. 2021.

[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.

[suzuki2026-15] Suzuki, H; Fukuda, N; Takeda, H; Shimizu, Y; Yoshimoto, M; Togano, Y; Sato, H; Kitamura, N; Momota, S; Kusaka, K; Yanagisawa, Y; Ohtake, M; Fukunishi, N; Michimasa, S (3 February 2026). "Discovery of Proton-Rich Radioactive Isotopes in the Z = 63–70 Region Produced by the Projectile Fragmentation of a 345-MeV/Nucleon 238U Beam". Progress of Theoretical and Experimental Physics. 2026 (2). doi:10.1093/ptep/ptaf190.

[152tb-20] Collins, S.M.; Köster, U.; Robinson, A.P.; Ivanov, P.; Cocolios, T.E.; Russell, B.; Fenwick, A.J.; Bernerd, C.; Stegemann, S.; Johnston, K.; Gerami, A.M.; Chrysalidis, K.; Mohamud, H.; Ramirez, N.; Bhaisare, A.; Mewburn-Crook, J.; Cullen, D.M.; Pietras, B.; Pells, S.; Dockx, K.; Stucki, N.; Regan, P.H. (2023). "Determination of the Terbium-152 half-life from mass-separated samples from CERN-ISOLDE and assessment of the radionuclide purity". Applied Radiation and Isotopes. 202 111044. Elsevier BV. Bibcode:2023AppRI.20211044C. doi:10.1016/j.apradiso.2023.111044. ISSN 0969-8043. PMID 37797447.

[21] "Adopted Levels for ¹⁵²Tb". NNDC Chart of Nuclides.

[22] Collins, S.M.; Robinson, A.P.; Ivanov, P.; Köster, U.; Cocolios, T.E.; Russell, B.; Webster, B.; Fenwick, A.J.; Duchemin, C.; Ramos, J.P.; Chevallay, E.; Jakobsson, U.; Stegemann, S.; Regan, P.H.; Stora, T. (2022). "Half-life determination of 155Tb from mass-separated samples produced at CERN-MEDICIS". Applied Radiation and Isotopes. 190 110480. doi:10.1016/j.apradiso.2022.110480. hdl:10138/350587. PMID 36209648.

[sumikama2026-24] Sumikama, Toshiyuki; Fukuda, Naoki; Kubo, Toshiyuki; Suzuki, Hiroshi; Takeda, Hiroyuki; Inabe, Naohito; Kameda, Daisuke; Ahn, Deuk Soon; Murai, Daichi; Yoshida, Koichi; Kusaka, Kensuke; Yanagisawa, Yoshiyuki; Ohtake, Masao; Shimizu, Yohei; Sato, Yuki; Sato, Hiromi; Otsu, Hideaki; Baba, Hidetada; Lorusso, Giuseppe; Söderström, Pär-Anders; Isobe, Tadaaki; Imai, Nobuaki; Mukai, Momo; Kimura, Sota; Miyatake, Hiroari; Iwasa, Naohito; Yagi, Ayumi; Yokoyama, Rin; Tarasov, Oleg Borisovich; Geissel, Hans (15 February 2026). "Expanding the Isotopic Frontier: Seven New Neutron-Rich Rare-Earth Isotopes Observed at RIKEN RI Beam Factory". Journal of the Physical Society of Japan. 95 (2). doi:10.7566/JPSJ.95.024202.

[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]

[8]

[9]

[10]

[n 13]

[11]

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

List of isotopes

See also

References