# Isotopes of barium

Naturally occurring barium ($_{56}$Ba) 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. This nuclide decays by double electron capture (absorbing two electrons and emitting two neutrinos), with a half-life of (0.5–2.7)×10$^{21}$ years (about 10$^{11}$ times the age of the universe).
There are a total of thirty-three known radioisotopes in addition to $^{130}$Ba. The longest-lived of these is $^{133}$Ba, which has a half-life of 10.51 years. All other radioisotopes have half-lives shorter than two weeks. The longest-lived isomer is $^{133m}$Ba, which has a half-life of 38.9 hours. The shorter-lived $^{137m}$Ba (half-life 2.55 minutes) arises as the decay product of the common fission product caesium-137.
Barium-114 is predicted to undergo cluster decay, emitting a nucleus of stable $^{12}$C to produce $^{102}$Sn. However this decay is not yet observed; the upper limit on the branching ratio of such decay is 0.0034%.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity | Natural abundance (mole fraction) | Natural abundance (mole fraction) |
| Nuclide | Excitation energy | Excitation energy | Excitation energy | Half-life | Decay mode | Daughter isotope | Spin and parity | Normal proportion | Range of variation |
| $^{114}$Ba | 56 | 58 | 113.95072(11) | 460(125) ms | β$^+$ (79%) | $^{114}$Cs | 0+ | | |
| $^{114}$Ba | 56 | 58 | 113.95072(11) | 460(125) ms | α (0.9%) | $^{110}$Xe | 0+ | | |
| $^{114}$Ba | 56 | 58 | 113.95072(11) | 460(125) ms | β$^+$, p (20%) | $^{113}$Xe | 0+ | | |
| $^{114}$Ba | 56 | 58 | 113.95072(11) | 460(125) ms | CD (<.0034%) | $^{102}$Sn, $^{12}$C | 0+ | | |
| $^{115}$Ba | 56 | 59 | 114.94748(22)# | 0.45(5) s | β$^+$ | $^{115}$Cs | 5/2+# | | |
| $^{115}$Ba | 56 | 59 | 114.94748(22)# | 0.45(5) s | β$^+$, p (>15%) | $^{114}$Xe | 5/2+# | | |
| $^{116}$Ba | 56 | 60 | 115.94162(22)# | 1.3(2) s | β$^+$ (97%) | $^{116}$Cs | 0+ | | |
| $^{116}$Ba | 56 | 60 | 115.94162(22)# | 1.3(2) s | β$^+$, p (3%) | $^{115}$Xe | 0+ | | |
| $^{117}$Ba | 56 | 61 | 116.93832(27) | 1.75(7) s | β$^+$ (87%) | $^{117}$Cs | (3/2+) | | |
| $^{117}$Ba | 56 | 61 | 116.93832(27) | 1.75(7) s | β$^+$, p (13%) | $^{116}$Xe | (3/2+) | | |
| $^{117}$Ba | 56 | 61 | 116.93832(27) | 1.75(7) s | β$^+$, α (0.024%) | $^{113}$I | (3/2+) | | |
| $^{118}$Ba | 56 | 62 | 117.93323(22)# | 5.2(2) s | β$^+$ | $^{118}$Cs | 0+ | | |
| $^{119}$Ba | 56 | 63 | 118.93066(21) | 5.4(3) s | β$^+$ (75%) | $^{119}$Cs | (3/2+) | | |
| $^{119}$Ba | 56 | 63 | 118.93066(21) | 5.4(3) s | β$^+$, p (25%) | $^{118}$Xe | (3/2+) | | |
| $^{119m}$Ba | 66.0 keV | 66.0 keV | 66.0 keV | 360(20) ns | IT | $^{119}$Ba | (5/2−) | | |
| $^{120}$Ba | 56 | 64 | 119.92604(32) | 24(2) s | β$^+$ | $^{120}$Cs | 0+ | | |
| $^{121}$Ba | 56 | 65 | 120.92405(15) | 29.7(15) s | β$^+$ (99.98%) | $^{121}$Cs | 5/2+ | | |
| $^{121}$Ba | 56 | 65 | 120.92405(15) | 29.7(15) s | β$^+$, p (0.02%) | $^{120}$Xe | 5/2+ | | |
| $^{122}$Ba | 56 | 66 | 121.91990(3) | 1.95(15) min | β$^+$ | $^{122}$Cs | 0+ | | |
| $^{123}$Ba | 56 | 67 | 122.918781(13) | 2.7(4) min | β$^+$ | $^{123}$Cs | 5/2+ | | |
| $^{123m}$Ba | 120.95(8) keV | 120.95(8) keV | 120.95(8) keV | 830(60) ns | IT | $^{123}$Ba | 1/2+# | | |
| $^{124}$Ba | 56 | 68 | 123.915094(13) | 11.0(5) min | β$^+$ | $^{124}$Cs | 0+ | | |
| $^{125}$Ba | 56 | 69 | 124.914472(12) | 3.3(3) min | β$^+$ | $^{125}$Cs | 1/2+ | | |
| $^{125m}$Ba | 120(20)# keV | 120(20)# keV | 120(20)# keV | 2.76(14) μs | IT | $^{125}$Ba | (7/2−) | | |
| $^{126}$Ba | 56 | 70 | 125.911250(13) | 100(2) min | β$^+$ | $^{126}$Cs | 0+ | | |
| $^{127}$Ba | 56 | 71 | 126.911091(12) | 12.7(4) min | β$^+$ | $^{127}$Cs | 1/2+ | | |
| $^{127m}$Ba | 80.32(11) keV | 80.32(11) keV | 80.32(11) keV | 1.93(7) s | IT | $^{127}$Ba | 7/2− | | |
| $^{128}$Ba | 56 | 72 | 127.9083524(17) | 2.43(5) d | EC | $^{128}$Cs | 0+ | | |
| $^{129}$Ba | 56 | 73 | 128.908683(11) | 2.23(11) h | β$^+$ | $^{129}$Cs | 1/2+ | | |
| $^{129m}$Ba | 8.42(6) keV | 8.42(6) keV | 8.42(6) keV | 2.135(10) h | β$^+$ | $^{129}$Cs | 7/2+ | | |
| $^{129m}$Ba | 8.42(6) keV | 8.42(6) keV | 8.42(6) keV | 2.135(10) h | IT | $^{129}$Ba | 7/2+ | | |
| $^{130}$Ba | 56 | 74 | 129.9063260(3) | ≈ 1×10$^{21}$ y | 2EC? | $^{130}$Xe | 0+ | 0.0011(1) | |
| $^{130m}$Ba | 2475.12(18) keV | 2475.12(18) keV | 2475.12(18) keV | 9.54(14) ms | IT | $^{130}$Ba | 8− | | |
| $^{131}$Ba | 56 | 75 | 130.9069463(4) | 11.52(1) d | β$^+$ | $^{131}$Cs | 1/2+ | | |
| $^{131m}$Ba | 187.995(9) keV | 187.995(9) keV | 187.995(9) keV | 14.26(9) min | IT | $^{131}$Ba | 9/2− | | |
| $^{132}$Ba | 56 | 76 | 131.9050612(11) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 0.0010(1) | |
| $^{133}$Ba | 56 | 77 | 132.9060074(11) | 10.5379(16) y | EC | $^{133}$Cs | 1/2+ | | |
| $^{133m}$Ba | 288.252(9) keV | 288.252(9) keV | 288.252(9) keV | 38.90(6) h | IT (99.99%) | $^{133}$Ba | 11/2− | | |
| $^{133m}$Ba | 288.252(9) keV | 288.252(9) keV | 288.252(9) keV | 38.90(6) h | EC (0.0104%) | $^{133}$Cs | 11/2− | | |
| $^{134}$Ba | 56 | 78 | 133.90450825(27) | Stable | Stable | Stable | 0+ | 0.0242(15) | |
| $^{134m}$Ba | 2957.2(5) keV | 2957.2(5) keV | 2957.2(5) keV | 2.61(13) μs | IT | $^{134}$Ba | 10+ | | |
| $^{135}$Ba | 56 | 79 | 134.90568845(26) | Stable | Stable | Stable | 3/2+ | 0.0659(10) | |
| $^{135m1}$Ba | 268.218(20) keV | 268.218(20) keV | 268.218(20) keV | 28.11(2) h | IT | $^{135}$Ba | 11/2− | | |
| $^{135m2}$Ba | 2388.0(5) keV | 2388.0(5) keV | 2388.0(5) keV | 1.06(4) ms | IT | $^{135}$Ba | (23/2+) | | |
| $^{136}$Ba | 56 | 80 | 135.90457580(26) | Stable | Stable | Stable | 0+ | 0.0785(24) | |
| $^{136m1}$Ba | 2030.535(18) keV | 2030.535(18) keV | 2030.535(18) keV | 308.4(19) ms | IT | $^{136}$Ba | 7− | | |
| $^{136m2}$Ba | 3357.19(25) keV | 3357.19(25) keV | 3357.19(25) keV | 91(2) ns | IT | $^{136}$Ba | 10+ | | |
| $^{137}$Ba | 56 | 81 | 136.90582721(27) | Stable | Stable | Stable | 3/2+ | 0.1123(23) | |
| $^{137m1}$Ba | 661.659(3) keV | 661.659(3) keV | 661.659(3) keV | 2.552(1) min | IT | $^{137}$Ba | 11/2− | | |
| $^{137m2}$Ba | 2349.1(5) keV | 2349.1(5) keV | 2349.1(5) keV | 589(20) ns | IT | $^{137}$Ba | (19/2−) | | |
| $^{138}$Ba | 56 | 82 | 137.90524706(27) | Stable | Stable | Stable | 0+ | 0.7170(29) | |
| $^{138m}$Ba | 2090.536(21) keV | 2090.536(21) keV | 2090.536(21) keV | 850(100) ns | IT | $^{138}$Ba | 6+ | | |
| $^{139}$Ba | 56 | 83 | 138.90884116(27) | 82.93(9) min | β$^−$ | $^{139}$La | 7/2− | | |
| $^{140}$Ba | 56 | 84 | 139.910608(8) | 12.7534(21) d | β$^−$ | $^{140}$La | 0+ | | |
| $^{141}$Ba | 56 | 85 | 140.914404(6) | 18.27(7) min | β$^−$ | $^{141}$La | 3/2− | | |
| $^{142}$Ba | 56 | 86 | 141.916433(6) | 10.6(2) min | β$^−$ | $^{142}$La | 0+ | | |
| $^{143}$Ba | 56 | 87 | 142.920625(7) | 14.5(3) s | β$^−$ | $^{143}$La | 5/2− | | |
| $^{144}$Ba | 56 | 88 | 143.922955(8) | 11.73(8) s | β$^−$ | $^{144}$La | 0+ | | |
| $^{145}$Ba | 56 | 89 | 144.927518(9) | 4.31(16) s | β$^−$ | $^{145}$La | 5/2− | | |
| $^{146}$Ba | 56 | 90 | 145.9303632(19) | 2.15(4) s | β$^−$ | $^{146}$La | 0+ | | |
| $^{147}$Ba | 56 | 91 | 146.935304(21) | 893(1) ms | β$^−$ (99.93%) | $^{147}$La | 5/2− | | |
| $^{147}$Ba | 56 | 91 | 146.935304(21) | 893(1) ms | β$^−$, n (0.07%) | $^{146}$La | 5/2− | | |
| $^{148}$Ba | 56 | 92 | 147.9382230(16) | 620(5) ms | β$^−$ (99.6%) | $^{148}$La | 0+ | | |
| $^{148}$Ba | 56 | 92 | 147.9382230(16) | 620(5) ms | β$^−$, n (0.4%) | $^{147}$La | 0+ | | |
| $^{149}$Ba | 56 | 93 | 148.9432840(27) | 349(4) ms | β$^−$ (96.1%) | $^{149}$La | 3/2−# | | |
| $^{149}$Ba | 56 | 93 | 148.9432840(27) | 349(4) ms | β$^−$, n (3.9%) | $^{148}$La | 3/2−# | | |
| $^{150}$Ba | 56 | 94 | 149.946441(6) | 258(5) ms | β$^−$ (99.0%) | $^{150}$La | 0+ | | |
| $^{150}$Ba | 56 | 94 | 149.946441(6) | 258(5) ms | β$^−$, n (1.0%) | $^{149}$La | 0+ | | |
| $^{151}$Ba | 56 | 95 | 150.95176(43)# | 167(5) ms | β$^−$ | $^{151}$La | 3/2−# | | |
| $^{151}$Ba | 56 | 95 | 150.95176(43)# | 167(5) ms | β$^−$, n? | $^{150}$La | 3/2−# | | |
| $^{152}$Ba | 56 | 96 | 151.95533(43)# | 139(8) ms | β$^−$ | $^{152}$La | 0+ | | |
| $^{152}$Ba | 56 | 96 | 151.95533(43)# | 139(8) ms | β$^−$, n? | $^{151}$La | 0+ | | |
| $^{153}$Ba | 56 | 97 | 152.96085(43)# | 113(39) ms | β$^−$ | $^{153}$La | 5/2−# | | |
| $^{153}$Ba | 56 | 97 | 152.96085(43)# | 113(39) ms | β$^−$, n? | $^{152}$La | 5/2−# | | |
| $^{153}$Ba | 56 | 97 | 152.96085(43)# | 113(39) ms | β$^−$, 2n? | $^{151}$La | 5/2−# | | |
| $^{154}$Ba | 56 | 98 | 153.96466(54)# | 53(48) ms | β$^−$ | $^{154}$La | 0+ | | |
| This table header & footer: view ||||||||||
* ↑ $^m$Ba – 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).
* ↑ Modes of decay: CD:Cluster decay EC:Electron capture IT:Isomeric transition n:Neutron emission 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.
* ↑ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
* ↑ Primordial radioisotope
* ↑ Believed to undergo β$^+$β$^+$ decay to $^{132}$Xe with a half-life over 3×10$^{20}$ years
* 1 2 3 4 5 6 7 Fission product