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Standard atomic weight Ar°(Ba) | |||||||||||||||||||||||||||||||||||||||||||||||||||
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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. [4] This nuclide decays by double electron capture (absorbing two electrons and emitting two neutrinos), with a half-life of (0.5–2.7)×1021 years (about 1011 times the age of the universe).
There are a total of thirty-three known radioisotopes in addition to 130Ba. The longest-lived of these is 133Ba, which has a half-life of 10.51 years. All other radioisotopes have half-lives shorter than two weeks. The longest-lived isomer is 133mBa, which has a half-life of 38.9 hours. The shorter-lived 137mBa (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 12C to produce 102Sn. However this decay is not yet observed; the upper limit on the branching ratio of such decay is 0.0034%.
Nuclide [n 1] |
Z | N |
Isotopic mass (
Da)
[5] [n 2] [n 3] |
Half-life |
Decay mode [n 4] |
Daughter isotope [n 5] [n 6] |
Spin and parity [n 7] [n 8] |
Natural abundance (mole fraction) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | Normal proportion | Range of variation | |||||||||||||||||
114Ba | 56 | 58 | 113.95072(11) | 530(230) ms [0.43(+30−15) s] |
β+, p (99.59%) | 113Xe | 0+ | ||||||||||||
α (.37%) | 110Xe | ||||||||||||||||||
β+ (.04%) | 114Cs | ||||||||||||||||||
CD (<.0034%) [n 9] | 102Sn, 12C | ||||||||||||||||||
115Ba | 56 | 59 | 114.94748(22)# | 0.45(5) s | β+ | 115Cs | (5/2+)# | ||||||||||||
β+, p | 114Xe | ||||||||||||||||||
116Ba | 56 | 60 | 115.94162(22)# | 1.3(2) s | β+ | 116Cs | 0+ | ||||||||||||
β+, p | 115Xe | ||||||||||||||||||
117Ba | 56 | 61 | 116.93832(27) | 1.75(7) s | β+ | 117Cs | (3/2)(+#) | ||||||||||||
β+, α | 113I | ||||||||||||||||||
β+, p | 116Xe | ||||||||||||||||||
118Ba | 56 | 62 | 117.93323(22)# | 5.2(2) s | β+ | 118Cs | 0+ | ||||||||||||
β+, p | 117Xe | ||||||||||||||||||
119Ba | 56 | 63 | 118.93066(21) | 5.4(3) s | β+ | 119Cs | (5/2+) | ||||||||||||
β+, p | 118Xe | ||||||||||||||||||
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 (.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(+) | ||||||||||||
124Ba | 56 | 68 | 123.915094(13) | 11.0(5) min | β+ | 124Cs | 0+ | ||||||||||||
125Ba | 56 | 69 | 124.914472(12) | 3.5(4) min | β+ | 125Cs | 1/2(+#) | ||||||||||||
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 | 80.33(12) keV | 1.9(2) s | IT | 127Ba | 7/2− | ||||||||||||||
128Ba | 56 | 72 | 127.9083524(17) | 2.43(5) d | β+ | 128Cs | 0+ | ||||||||||||
129Ba | 56 | 73 | 128.908683(11) | 2.23(11) h | β+ | 129Cs | 1/2+ | ||||||||||||
129mBa | 8.42(6) keV | 2.16(2) h | β+ | 129Cs | 7/2+# | ||||||||||||||
IT | 129Ba | ||||||||||||||||||
130Ba [n 10] | 56 | 74 | 129.9063260(3) | 1.6(±1.1)×1021 y | Double EC | 130Xe | 0+ | 0.00106(1) | |||||||||||
130mBa | 2475.12(18) keV | 9.54(14) ms | IT | 130Ba | 8− | ||||||||||||||
131Ba | 56 | 75 | 130.9069463(4) | 11.50(6) d | β+ | 131Cs | 1/2+ | ||||||||||||
131mBa | 187.14(12) keV | 14.6(2) min | IT | 131Ba | 9/2− | ||||||||||||||
132Ba | 56 | 76 | 131.9050612(11) | Observationally Stable [n 11] | 0+ | 0.00101(1) | |||||||||||||
133Ba | 56 | 77 | 132.9060074(11) | 10.51(5) y | EC | 133Cs | 1/2+ | ||||||||||||
133mBa | 288.247(9) keV | 38.9(1) h | IT (99.99%) | 133Ba | 11/2− | ||||||||||||||
EC (.0096%) | 133Cs | ||||||||||||||||||
134Ba | 56 | 78 | 133.90450825(27) | Stable | 0+ | 0.02417(18) | |||||||||||||
135Ba | 56 | 79 | 134.90568845(26) | Stable | 3/2+ | 0.06592(12) | |||||||||||||
135mBa | 268.22(2) keV | 28.7(2) h | IT | 135Ba | 11/2− | ||||||||||||||
136Ba | 56 | 80 | 135.90457580(26) | Stable | 0+ | 0.07854(24) | |||||||||||||
136mBa | 2030.466(18) keV | 308.4(19) ms | IT | 136Ba | 7− | ||||||||||||||
137Ba | 56 | 81 | 136.90582721(27) | Stable | 3/2+ | 0.11232(24) | |||||||||||||
137m1Ba | 661.659(3) keV | 2.552(1) min | IT | 137Ba | 11/2− | ||||||||||||||
137m2Ba | 2349.1(4) keV | 0.59(10) µs | (17/2−) | ||||||||||||||||
138Ba [n 12] | 56 | 82 | 137.90524706(27) | Stable | 0+ | 0.71698(42) | |||||||||||||
138mBa | 2090.54(6) keV | 800(100) ns | 6+ | ||||||||||||||||
139Ba [n 12] | 56 | 83 | 138.90884116(27) | 83.06(28) min | β− | 139La | 7/2− | ||||||||||||
140Ba [n 12] | 56 | 84 | 139.910608(8) | 12.752(3) d | β− | 140La | 0+ | ||||||||||||
141Ba [n 12] | 56 | 85 | 140.914404(6) | 18.27(7) min | β− | 141La | 3/2− | ||||||||||||
142Ba [n 12] | 56 | 86 | 141.916433(6) | 10.6(2) min | β− | 142La | 0+ | ||||||||||||
143Ba [n 12] | 56 | 87 | 142.920625(7) | 14.5(3) s | β− | 143La | 5/2− | ||||||||||||
144Ba [n 12] | 56 | 88 | 143.922955(8) | 11.5(2) s | β− | 144La | 0+ | ||||||||||||
145Ba | 56 | 89 | 144.927518(9) | 4.31(16) s | β− | 145La | 5/2− | ||||||||||||
146Ba | 56 | 90 | 145.9303632(19) | 2.22(7) s | β− (99.98%) | 146La | 0+ | ||||||||||||
β−, n (.02%) | 145La | ||||||||||||||||||
147Ba | 56 | 91 | 146.935304(21) | 0.893(1) s | β− (99.94%) | 147La | (3/2+) | ||||||||||||
β−, n (.06%) | 146La | ||||||||||||||||||
148Ba | 56 | 92 | 147.9382230(16) | 0.612(17) s | β− (99.6%) | 148La | 0+ | ||||||||||||
β−, n (.4%) | 147La | ||||||||||||||||||
149Ba | 56 | 93 | 148.9432840(27) | 344(7) ms | β− (99.57%) | 149La | 3/2−# | ||||||||||||
β−, n (.43%) | 148La | ||||||||||||||||||
150Ba | 56 | 94 | 149.946441(6) | 300 ms | β− | 150La | 0+ | ||||||||||||
β−, n (rare) | 149La | ||||||||||||||||||
151Ba | 56 | 95 | 150.95176(43)# | 200# ms [>300 ns] | β− | 151La | 3/2−# | ||||||||||||
152Ba | 56 | 96 | 151.95533(43)# | 100# ms | β− | 152La | 0+ | ||||||||||||
153Ba | 56 | 97 | 152.96085(43)# | 80# ms | β− | 153La | 5/2−# | ||||||||||||
154Ba | 56 | 98 | 153.96466(54)# | 53(48) ms | β− | 154La | 0+ | ||||||||||||
This table header & footer: |
CD: | Cluster decay |
EC: | Electron capture |
IT: | Isomeric transition |
n: | Neutron emission |
p: | Proton emission |