Isotopes of barium

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Main isotopes of barium (56Ba)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
130Ba 0.11% (0.5–2.7)×1021 y εε 130Xe
132Ba 0.10% stable
133Ba syn 10.51 y ε 133Cs
134Ba 2.42% stable
135Ba 6.59% stable
136Ba 7.85% stable
137Ba 11.23% stable
138Ba 71.70% stable
Standard atomic weight Ar, standard(Ba)

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.[2] 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, though 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[edit]

Nuclide
[n 1]
Z N Isotopic mass (u)
[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 58 113.95068(15) 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 59 114.94737(64)# 0.45(5) s β+ 115Cs (5/2+)#
β+, p 114Xe
116Ba 56 60 115.94138(43)# 1.3(2) s β+ 116Cs 0+
β+, p 115Xe
117Ba 56 61 116.93850(32)# 1.75(7) s β+ 117Cs (3/2)(+#)
β+, α 113I
β+, p 116Xe
118Ba 56 62 117.93304(21)# 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 69 124.914473(12) 3.5(4) min β+ 125Cs 1/2(+#)
126Ba 56 70 125.911250(13) 100(2) min β+ 126Cs 0+
127Ba 56 71 126.911094(12) 12.7(4) min β+ 127Cs 1/2+
127mBa 80.33(12) keV 1.9(2) s IT 127Ba 7/2−
128Ba 56 72 127.908318(11) 2.43(5) d β+ 128Cs 0+
129Ba 56 73 128.908679(12) 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 74 129.9063208(30) 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 75 130.906941(3) 11.50(6) d β+ 131Cs 1/2+
131mBa 187.14(12) keV 14.6(2) min IT 131Ba 9/2−
132Ba 56 76 131.9050613(11) Observationally Stable[n 11] 0+ 0.00101(1)
133Ba 56 77 132.9060075(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 78 133.9045084(4) Stable 0+ 0.02417(18)
135Ba 56 79 134.9056886(4) Stable 3/2+ 0.06592(12)
135mBa 268.22(2) keV 28.7(2) h IT 135Ba 11/2−
136Ba 56 80 135.9045759(4) Stable 0+ 0.07854(24)
136mBa 2030.466(18) keV 308.4(19) ms IT 136Ba 7−
137Ba 56 81 136.9058274(5) 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 82 137.9052472(5) Stable 0+ 0.71698(42)
138mBa 2090.54(6) keV 800(100) ns 6+
139Ba[n 12] 56 83 138.9088413(5) 83.06(28) min β 139La 7/2−
140Ba[n 12] 56 84 139.910605(9) 12.752(3) d β 140La 0+
141Ba[n 12] 56 85 140.914411(9) 18.27(7) min β 141La 3/2−
142Ba[n 12] 56 86 141.916453(7) 10.6(2) min β 142La 0+
143Ba[n 12] 56 87 142.920627(14) 14.5(3) s β 143La 5/2−
144Ba[n 12] 56 88 143.922953(14) 11.5(2) s β 144La 0+
145Ba 56 89 144.92763(8) 4.31(16) s β 145La 5/2−
146Ba 56 90 145.93022(8) 2.22(7) s β (99.98%) 146La 0+
β, n (.02%) 145La
147Ba 56 91 146.93495(22)# 0.893(1) s β (99.94%) 147La (3/2+)
β, n (.06%) 146La
148Ba 56 92 147.93772(9) 0.612(17) s β (99.6%) 148La 0+
β, n (.4%) 147La
149Ba 56 93 148.94258(21)# 344(7) ms β (99.57%) 149La 3/2−#
β, n (.43%) 148La
150Ba 56 94 149.94568(43)# 300 ms β 150La 0+
β, n (rare) 149La
151Ba 56 95 150.95081(43)# 200# ms [>300 ns] β 151La 3/2−#
152Ba 56 96 151.95427(54)# 100# ms β 152La 0+
153Ba 56 97 152.95961(86)# 80# ms β 153La 5/2−#
  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. ^ a b c d e f g Fission product

See also[edit]

References[edit]

  1. ^ Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  2. ^ 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. doi:10.1103/PhysRevC.64.035205.