Isotopes of terbium

Naturally occurring terbium (₆₅Tb) is composed of one stable isotope, ¹⁵⁹Tb. Thirty-six 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).

Main isotopes of terbium (₆₅Tb)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^157Tb syn 71 y ε ^157Gd ^158Tb syn 180 y ε ^158Gd β^− ^158Dy ^159Tb 100% stable
Standard atomic weight Ar, standard(Tb)	158.92535(2)[1]

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 behind 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)
	Excitation energy[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
					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
					β^+, p (.26%)	^139Eu
^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^+	^142Gd	1+
					β^+, p	^141Eu
^142m1Tb	280.2(10) keV			303(17) ms	IT (99.5%)	^142Tb	(5−)
					β^+ (.5%)	^142Gd
^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+
					β^+, p (rare)	^143Eu
^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+
					α (16.7%)	^145Eu
^149mTb	35.78(13) keV			4.16(4) min	β^+ (99.97%)	^149Gd	11/2−
					α (.022%)	^145Eu
^150Tb	65	85	149.923660(8)	3.48(16) h	β^+ (99.95%)	^150Gd	(2−)
					α (.05%)	^146Eu
^150mTb	457(29) keV			5.8(2) min	β^+	^150Gd	9+
					IT (rare)	^150Tb
^151Tb	65	86	150.923103(5)	17.609(1) h	β^+ (99.99%)	^151Gd	1/2(+)
					α (.0095%)	^147Eu
^151mTb	99.54(6) keV			25(3) s	IT (93.8%)	^151Tb	(11/2−)
					β^+ (6.2%)	^151Gd
^152Tb	65	87	151.92407(4)	17.5(1) h	β^+	^152Gd	2−
					α (7×10^−7%)	^148Eu
^152m1Tb	342.15(16) keV			0.96 µs			5−
^152m2Tb	501.74(19) keV			4.2(1) min	IT (78.8%)	^152Tb	8+
					β^+ (21.2%)	^152Gd
^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(+#)
					β^− (.1%)	^154Dy
^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−
					β^− (rare)	^156Dy
^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−
					β^− (16.6%)	^158Dy
^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)#	2# s	β^−	^169Dy	3/2+#
^170Tb	65	105	169.95025(75)#	3# s	β^−	^170Dy
^171Tb	65	106	170.95330(86)#	500# ms	β^−	^171Dy	3/2+#

1. ^mTb – 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

References

1. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.

• 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.