Isotopes of terbium

Isotopes of terbium (₆₅Tb)
β−	158Dy
Standard atomic weight Ar°(Tb)
	158.925354±0.000007; 158.93±0.01 (abridged);
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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 6.907 days, 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 ^156m1Tb (t_1/2 = 24.4 hours), ^154m2Tb (t_1/2 = 22.7 hours) and ^154m1Tb (t_1/2 = 9.4 hours).

The primary decay mode before the most abundant stable isotope, ¹⁵⁹Tb, is electron capture, and the primary mode behind is beta decay. The primary decay products before ¹⁵⁹Tb are element Gd (gadolinium) isotopes, and the primary products after ¹⁵⁹Tb are element Dy (dysprosium) isotopes.

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]}	Natural abundance (mole fraction)
Nuclide ^{[n 1]}	Excitation energy^{[n 4]}			Half-life ^{[n 4]}	Decay mode ^{[n 5]}	Daughter isotope ^{[n 6]}^{[n 7]}	Spin and parity ^{[n 8]}^{[n 4]}	Normal proportion	Range of variation
¹³⁵Tb	65	70		0.94(+33−22) ms			(7/2−)
¹³⁶Tb	65	71	135.96138(64)#	0.2# s
¹³⁷Tb	65	72	136.95598(64)#	600# ms			11/2−#
¹³⁸Tb	65	73	137.95316(43)#	800# ms [>200 ns]	β⁺	¹³⁸Gd
¹³⁸Tb	65	73	137.95316(43)#	800# ms [>200 ns]	p	¹³⁷Gd
¹³⁹Tb	65	74	138.94829(32)#	1.6(2) s	β⁺	¹³⁹Gd	11/2−#
¹⁴⁰Tb	65	75	139.94581(86)	2.4(2) s	β⁺ (99.74%)	¹⁴⁰Gd	5
¹⁴⁰Tb	65	75	139.94581(86)	2.4(2) s	β⁺, p (.26%)	¹³⁹Eu	5
¹⁴¹Tb	65	76	140.94145(11)	3.5(2) s	β⁺	¹⁴¹Gd	(5/2−)
^141mTb	0(200)# keV			7.9(6) s	β⁺	¹⁴¹Gd	11/2−#
¹⁴²Tb	65	77	141.93874(32)#	597(17) ms	β⁺ (96.8(4)%)	¹⁴²Gd	1+
					EC (3.2(4)%)	¹⁴²Gd
					β⁺, p	¹⁴¹Eu
^142m1Tb	280.2(10) keV			303(17) ms	IT (99.5%)	¹⁴²Tb	(5−)
^142m1Tb	280.2(10) keV			303(17) ms	β⁺ (.5%)	¹⁴²Gd	(5−)
^142m2Tb	621.4(11) keV			15(4) μs
¹⁴³Tb	65	78	142.93512(6)	12(1) s	β⁺	¹⁴³Gd	(11/2−)
^143mTb	0(100)# keV			<21 s	β⁺	¹⁴³Gd	5/2+#
¹⁴⁴Tb	65	79	143.93305(3)	~1 s	β⁺	¹⁴⁴Gd	1+
¹⁴⁴Tb	65	79	143.93305(3)	~1 s	β⁺, p (rare)	¹⁴³Eu	1+
^144m1Tb	396.9(5) keV			4.25(15) s	IT (66%)	¹⁴⁴Tb	(6−)
					β⁺ (34%)	¹⁴⁴Gd
					β⁺, p (<1%)	¹⁴³Eu
^144m2Tb	476.2(5) keV			2.8(3) μs			(8−)
^144m3Tb	517.1(5) keV			670(60) ns			(9+)
^144m4Tb	544.5(6) keV			<300 ns			(10+)
¹⁴⁵Tb	65	80	144.92927(6)	20# min	β⁺	¹⁴⁵Gd	(3/2+)
^145mTb	0(100)# keV			30.9(7) s	β⁺	¹⁴⁵Gd	(11/2−)
¹⁴⁶Tb	65	81	145.92725(5)	8(4) s	β⁺	¹⁴⁶Gd	1+
^146m1Tb	150(100)# keV			24.1(5) s	β⁺	¹⁴⁶Gd	5−
^146m2Tb	930(100)# keV			1.18(2) ms			(10+)
¹⁴⁷Tb	65	82	146.924045(13)	1.64(3) h	β⁺	¹⁴⁷Gd	1/2+#
^147mTb	50.6(9) keV			1.87(5) min	β⁺	¹⁴⁷Gd	(11/2)−
¹⁴⁸Tb	65	83	147.924272(15)	60(1) min	β⁺	¹⁴⁸Gd	2−
^148m1Tb	90.1(3) keV			2.20(5) min	β⁺	¹⁴⁸Gd	(9)+
^148m2Tb	8618.6(10) keV			1.310(7) μs			(27+)
¹⁴⁹Tb	65	84	148.923246(5)	4.118(25) h	β⁺ (83.3%)	¹⁴⁹Gd	1/2+
¹⁴⁹Tb	65	84	148.923246(5)	4.118(25) h	α (16.7%)	¹⁴⁵Eu	1/2+
^149mTb	35.78(13) keV			4.16(4) min	β⁺ (99.97%)	¹⁴⁹Gd	11/2−
^149mTb	35.78(13) keV			4.16(4) min	α (.022%)	¹⁴⁵Eu	11/2−
¹⁵⁰Tb	65	85	149.923660(8)	3.48(16) h	β⁺ (99.95%)	¹⁵⁰Gd	(2−)
¹⁵⁰Tb	65	85	149.923660(8)	3.48(16) h	α (.05%)	¹⁴⁶Eu	(2−)
^150mTb	457(29) keV			5.8(2) min	β⁺	¹⁵⁰Gd	9+
^150mTb	457(29) keV			5.8(2) min	IT (rare)	¹⁵⁰Tb	9+
¹⁵¹Tb	65	86	150.923103(5)	17.609(1) h	β⁺ (99.99%)	¹⁵¹Gd	1/2(+)
¹⁵¹Tb	65	86	150.923103(5)	17.609(1) h	α (.0095%)	¹⁴⁷Eu	1/2(+)
^151mTb	99.54(6) keV			25(3) s	IT (93.8%)	¹⁵¹Tb	(11/2−)
^151mTb	99.54(6) keV			25(3) s	β⁺ (6.2%)	¹⁵¹Gd	(11/2−)
¹⁵²Tb	65	87	151.92407(4)	17.8784(95) h^[4]	β⁺	¹⁵²Gd	2−
¹⁵²Tb	65	87	151.92407(4)	17.8784(95) h^[4]	α (7×10⁻⁷%)	¹⁴⁸Eu	2−
^152m1Tb	342.15(16) keV			0.96 μs			5−
^152m2Tb	501.74(19) keV			4.2(1) min	IT (78.8%)	¹⁵²Tb	8+
^152m2Tb	501.74(19) keV			4.2(1) min	β⁺ (21.2%)	¹⁵²Gd	8+
¹⁵³Tb	65	88	152.923435(5)	2.34(1) d	β⁺	¹⁵³Gd	5/2+
^153mTb	163.175(5) keV			186(4) μs			11/2−
¹⁵⁴Tb	65	89	153.92468(5)	21.5(4) h	β⁺ (99.9%)	¹⁵⁴Gd	0(+#)
¹⁵⁴Tb	65	89	153.92468(5)	21.5(4) h	β⁻ (.1%)	¹⁵⁴Dy	0(+#)
^154m1Tb	12(7) keV			9.4(4) h	β⁺ (78.2%)	¹⁵⁴Gd	3−
					IT (21.8%)	¹⁵⁴Tb
					β⁻ (.1%)	¹⁵⁴Dy
^154m2Tb	200(150)# keV			22.7(5) h			7−
^154m3Tb	0+Z keV			513(42) ns
¹⁵⁵Tb	65	90	154.923505(13)	5.32(6) d	EC	¹⁵⁵Gd	3/2+
¹⁵⁶Tb	65	91	155.924747(5)	5.35(10) d	β⁺	¹⁵⁶Gd	3−
¹⁵⁶Tb	65	91	155.924747(5)	5.35(10) d	β⁻ (rare)	¹⁵⁶Dy	3−
^156m1Tb	54(3) keV			24.4(10) h	IT	¹⁵⁶Tb	(7−)
^156m2Tb	88.4(2) keV			5.3(2) h			(0+)
¹⁵⁷Tb	65	92	156.9240246(27)	71(7) y	EC	¹⁵⁷Gd	3/2+
¹⁵⁸Tb	65	93	157.9254131(28)	180(11) y	β⁺ (83.4%)	¹⁵⁸Gd	3−
¹⁵⁸Tb	65	93	157.9254131(28)	180(11) y	β⁻ (16.6%)	¹⁵⁸Dy	3−
^158m1Tb	110.3(12) keV			10.70(17) s	IT (99.39%)	¹⁵⁸Tb	0−
					β⁻ (.6%)	¹⁵⁸Dy
					β⁺ (.01%)	¹⁵⁸Gd
^158m2Tb	388.37(15) keV			0.40(4) ms			7−
¹⁵⁹Tb^{[n 9]}	65	94	158.9253468(27)	Stable			3/2+	1.0000
¹⁶⁰Tb	65	95	159.9271676(27)	72.3(2) d	β⁻	¹⁶⁰Dy	3−
¹⁶¹Tb^{[n 9]}	65	96	160.9275699(28)	6.906(19) d	β⁻	¹⁶¹Dy	3/2+
¹⁶²Tb	65	97	161.92949(4)	7.60(15) min	β⁻	¹⁶²Dy	1−
¹⁶³Tb	65	98	162.930648(5)	19.5(3) min	β⁻	¹⁶³Dy	3/2+
¹⁶⁴Tb	65	99	163.93335(11)	3.0(1) min	β⁻	¹⁶⁴Dy	(5+)
¹⁶⁵Tb	65	100	164.93488(21)#	2.11(10) min	β⁻	^165mDy	3/2+#
¹⁶⁶Tb	65	101	165.93799(11)	25.6(22) s	β⁻	¹⁶⁶Dy
¹⁶⁷Tb	65	102	166.94005(43)#	19.4(27) s	β⁻	¹⁶⁷Dy	3/2+#
¹⁶⁸Tb	65	103	167.94364(54)#	8.2(13) s	β⁻	¹⁶⁸Dy	4−#
¹⁶⁹Tb	65	104	168.94622(64)#	5.13(32) s	β⁻	¹⁶⁹Dy	3/2+#
¹⁷⁰Tb	65	105	169.95025(75)#	960(78) ms	β⁻	¹⁷⁰Dy
¹⁷¹Tb	65	106	170.95330(86)#	1.23(10) s	β⁻	¹⁷¹Dy	3/2+#
¹⁷²Tb	65	107		760(190) ms	β⁻	¹⁷²Dy	6+#
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References

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.
"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
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.

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