Isotopes of barium

Naturally occurring barium (₅₆Ba) is a mix of six stable isotopes and one very long-lived radioactive primordial isotope, barium-130, identified as being unstable by geochemical means (from analysis of the presence of its daughter xenon-130 in rocks) in 2001, presumably decaying by double electron capture with a half-life of (0.5–2.7)×10²¹ years (about 10¹¹ times the age of the universe). The two measurements are discordant; the above reflects the total range, the value in the table below is a crude average.

Isotopes of barium (₅₆Ba)

Main isotopes Decay Isotope abun­dance half-life (t1/2) mode pro­duct ^130Ba 0.11% (0.5–2.7)×10^21 y εε ^130Xe ^131Ba synth 11.52 d β^+ ^131Cs ^132Ba 0.1% stable ^133Ba synth 10.538 y ε ^133Cs ^134Ba 2.42% stable ^135Ba 6.59% stable ^136Ba 7.85% stable ^137Ba 11.2% stable ^138Ba 71.7% stable ^140Ba synth 12.753 d β^− ^140La
Standard atomic weight Ar°(Ba)
	137.327±0.007 137.33±0.01 (abridged)
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With the total range of mass numbers known 114 to 154, there are thirty-three known radioisotopes in addition to ¹³⁰Ba. The longest-lived of these is ¹³³Ba, which has a half-life of 10.538 years; all others have half-lives shorter than two weeks. The longest-lived isomers are ^133mBa at 38.90 hours and ^135m1Ba at 28.11 hours. The analogous ^137m1Ba (half-life 2.552 minutes) occurs in the decay of the common fission product caesium-137.

Barium-114 is theorized to undergo cluster decay, emitting a nucleus of stable ¹²C to produce ¹⁰²Sn. This decay has not been observed, with only an upper limit on the branching ratio of such decay (0.0034%).

List of isotopes

Nuclide	Z	N	Isotopic mass (Da)	Half-life	Decay mode	Daughter isotope	Spin and parity	Natural abundance (mole fraction)
	Excitation energy							Normal proportion	Range of variation
^114Ba	56	58	113.95072(11)	460(125) ms	β^+ (79%)	^114Cs	0+
					α (0.9%)	^110Xe
					β^+, p (20%)	^113Xe
					CD (<.0034%)	^102Sn, ^12C
^115Ba	56	59	114.94748(22)#	0.45(5) s	β^+	^115Cs	5/2+#
					β^+, p (>15%)	^114Xe
^116Ba	56	60	115.94162(22)#	1.3(2) s	β^+ (97%)	^116Cs	0+
					β^+, p (3%)	^115Xe
^117Ba	56	61	116.93832(27)	1.75(7) s	β^+ (87%)	^117Cs	(3/2+)
					β^+, p (13%)	^116Xe
					β^+, α (0.024%)	^113I
^118Ba	56	62	117.93323(22)#	5.2(2) s	β^+	^118Cs	0+
^119Ba	56	63	118.93066(21)	5.4(3) s	β^+ (75%)	^119Cs	(3/2+)
					β^+, p (25%)	^118Xe
^119mBa	66.0 keV			360(20) ns	IT	^119Ba	(5/2−)
^120Ba	56	64	119.92604(32)	24(2) s	β^+	^120Cs	0+
^121Ba	56	65	120.92405(15)	29.7(15) s	β^+ (99.98%)	^121Cs	5/2+
					β^+, p (0.02%)	^120Xe
^122Ba	56	66	121.91990(3)	1.95(15) min	β^+	^122Cs	0+
^123Ba	56	67	122.918781(13)	2.7(4) min	β^+	^123Cs	5/2+
^123mBa	120.95(8) keV			830(60) ns	IT	^123Ba	1/2+#
^124Ba	56	68	123.915094(13)	11.0(5) min	β^+	^124Cs	0+
^125Ba	56	69	124.914472(12)	3.3(3) min	β^+	^125Cs	1/2+
^125mBa	120(20)# keV			2.76(14) μs	IT	^125Ba	(7/2−)
^126Ba	56	70	125.911250(13)	100(2) min	β^+	^126Cs	0+
^127Ba	56	71	126.911091(12)	12.7(4) min	β^+	^127Cs	1/2+
^127mBa	80.32(11) keV			1.93(7) s	IT	^127Ba	7/2−
^128Ba	56	72	127.9083524(17)	2.43(5) d	EC	^128Cs	0+
^129Ba	56	73	128.908683(11)	2.23(11) h	β^+	^129Cs	1/2+
^129mBa	8.42(6) keV			2.135(10) h	β^+	^129Cs	7/2+
					IT?	^129Ba
^130Ba	56	74	129.9063260(3)	≈ 1×10^21 y	εε	^130Xe	0+	0.0011(1)
^130mBa	2475.12(18) keV			9.54(14) ms	IT	^130Ba	8−
^131Ba	56	75	130.9069463(4)	11.52(1) d	β^+	^131Cs	1/2+
^131mBa	187.995(9) keV			14.26(9) min	IT	^131Ba	9/2−
^132Ba	56	76	131.9050612(11)	Observationally Stable			0+	0.0010(1)
^133Ba	56	77	132.9060074(11)	10.5379(16) y	EC	^133Cs	1/2+
^133mBa	288.252(9) keV			38.90(6) h	IT (99.99%)	^133Ba	11/2−
					EC (0.0104%)	^133Cs
^134Ba	56	78	133.90450825(27)	Stable			0+	0.0242(15)
^134mBa	2957.2(5) keV			2.61(13) μs	IT	^134Ba	10+
^135Ba	56	79	134.90568845(26)	Stable			3/2+	0.0659(10)
^135m1Ba	268.218(20) keV			28.11(2) h	IT	^135Ba	11/2−
^135m2Ba	2388.0(5) keV			1.06(4) ms	IT	^135Ba	(23/2+)
^136Ba	56	80	135.90457580(26)	Stable			0+	0.0785(24)
^136m1Ba	2030.535(18) keV			308.4(19) ms	IT	^136Ba	7−
^136m2Ba	3357.19(25) keV			91(2) ns	IT	^136Ba	10+
^137Ba	56	81	136.90582721(27)	Stable			3/2+	0.1123(23)
^137m1Ba	661.659(3) keV			2.552(1) min	IT	^137Ba	11/2−
^137m2Ba	2349.1(5) keV			589(20) ns	IT	^137Ba	(19/2−)
^138Ba	56	82	137.90524706(27)	Stable			0+	0.7170(29)
^138mBa	2090.536(21) keV			850(100) ns	IT	^138Ba	6+
^139Ba	56	83	138.90884116(27)	82.93(9) min	β^−	^139La	7/2−
^140Ba	56	84	139.910608(8)	12.7534(21) d	β^−	^140La	0+
^141Ba	56	85	140.914404(6)	18.27(7) min	β^−	^141La	3/2−
^142Ba	56	86	141.916433(6)	10.6(2) min	β^−	^142La	0+
^143Ba	56	87	142.920625(7)	14.5(3) s	β^−	^143La	5/2−
^144Ba	56	88	143.922955(8)	11.73(8) s	β^−	^144La	0+
^145Ba	56	89	144.927518(9)	4.31(16) s	β^−	^145La	5/2−
^146Ba	56	90	145.9303632(19)	2.15(4) s	β^−	^146La	0+
^147Ba	56	91	146.935304(21)	893(1) ms	β^− (99.93%)	^147La	5/2−
					β^−, n (0.07%)	^146La
^148Ba	56	92	147.9382230(16)	620(5) ms	β^− (99.6%)	^148La	0+
					β^−, n (0.4%)	^147La
^149Ba	56	93	148.9432840(27)	349(4) ms	β^− (96.1%)	^149La	3/2−#
					β^−, n (3.9%)	^148La
^150Ba	56	94	149.946441(6)	258(5) ms	β^− (99.0%)	^150La	0+
					β^−, n (1.0%)	^149La
^151Ba	56	95	150.95176(43)#	167(5) ms	β^−	^151La	3/2−#
					β^−, n?	^150La
^152Ba	56	96	151.95533(43)#	139(8) ms	β^−	^152La	0+
					β^−, n?	^151La
^153Ba	56	97	152.96085(43)#	113(39) ms	β^−	^153La	5/2−#
					β^−, n?	^152La
					β^−, 2n?	^151La
^154Ba	56	98	153.96466(54)#	53(48) ms	β^−	^154La	0+
This table header & footer: view

1. ^mBa – 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. Modes of decay:

   EC:	Electron capture
   CD:	Cluster decay
   IT:	Isomeric transition
   n:	Neutron emission
   p:	Proton emission

5. Bold italics symbol as daughter – Daughter product is nearly stable.
6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.
8. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
9. Primordial radionuclide
10. Believed to undergo β⁺β⁺ decay to ¹³²Xe with a half-life over 3×10²⁰ years
11. Fission product

See also

Daughter products other than barium

• Isotopes of lanthanum
• Isotopes of caesium
• Isotopes of xenon
• Isotopes of iodine
• Isotopes of tin
• Isotopes of carbon