Isotopes of terbium

Naturally occurring terbium (Tb) is composed of 1 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).

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.

Relative atomic mass: 158.92535(2).

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[1][n 1]	daughter isotope(s)[n 2]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
^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 3]	65	94	158.9253468(27)	Stable[n 4]			3/2+	1.0000
^160Tb	65	95	159.9271676(27)	72.3(2) d	β^−	^160Dy	3−
^161Tb[n 3]	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. Abbreviations:
   EC: Electron capture
   IT: Isomeric transition
2. Bold for stable isotopes
3. Fission product
4. Theoretically capable of spontaneous fission

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

References

1. "Universal Nuclide Chart". nucleonica. (registration required (help)).

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). 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:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • M. E. Wieser (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. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. Check date values in: |access-date= (help)
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.