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.[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).

Isotopes of barium (56Ba)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
130Ba 0.11% (0.5–2.7)×1021 y εε 130Xe
132Ba 0.1% stable
133Ba synth 10.51 y ε 133Cs
134Ba 2.42% stable
135Ba 6.59% stable
136Ba 7.85% stable
137Ba 11.2% stable
138Ba 71.7% stable
Standard atomic weight Ar°(Ba)

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%.

List of isotopes


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:
  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:
    CD:Cluster decay
    EC:Electron capture
    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. Cluster decay is predicted but had never been observed.
  10. Primordial radioisotope
  11. Believed to undergo β+β+ decay to 132Xe with a half-life over 300×1018 years
  12. Fission product

References
  1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. "Standard Atomic Weights: Barium". CIAAW. 1985.
  3. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. Meshik, A.P.; Hohenberg, C.M.; Pravdivtseva, O.V.; Kapusta, Y.S. (2001). "Weak decay of 130Ba and 132Ba: Geochemical measurements". Physical Review C. 64 (3): 035205–1–035205–6. Bibcode:2001PhRvC..64c5205M. doi:10.1103/PhysRevC.64.035205.
  5. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
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