Isotopes of barium
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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.
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) | Discovery year | Half-life | Decay mode | Daughter isotope | Spin and parity | Natural abundance (molefraction) | |
|---|---|---|---|---|---|---|---|---|---|---|
| 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 | 66.0keV | 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) | ≈1×1021y | 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 | (2004) | 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+ | |||
| 155Ba | 56 | 99 | ||||||||
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Barium-131
Barium-131 is a radioactive isotope of barium with a half-life of 11.52 days. It decays to caesium-131 by electron capture. It is produced by irradiation of caesium with protons with the reaction 133Cs(p,3n)131Ba. It is developed for SPECT imaging and can be combined with the alpha-emitter radium-223.
See also
Daughter products other than barium