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Isotopes of Cesium

List, data and properties of all known isotopes of Cesium.

Content
Atomic properties
Decay properties
NMR active nuclides
Radiation protection
References
Cesium isotopes

All atomic nuclei of the chemical element cesium (also: caesium) are summarized under cesium isotopes; these all consist of an atomic nucleus with 55 protons and, in the uncharged state, 55 electrons. The difference between the individual cesium isotopes is based on the number of neutrons in the nucleus.

Cesium, Cs, is a so-called mononuclide element or pure element, i. H. Cesium occurs in nature only in the form of the cesium isotope 133Cs; a total of 39 cesium isotopes and 23 nuclear isomers are known.

 

Isotope Table: Cesium

The two following tables list the most important data and properties of the Cesium isotopes. Further information on the individual Cesium isotopes is listed on separate pages and can be accessed via the link in column 1.

 

Atomic Properties

Isotope
Nuclide		ENAtomic Mass
[Nuclear Mass]
{Mass Excess}		Spin I
(h/2π)		Parent
123456
Cesium-11211255Cs57111.95031(9) u
[111.9201401 u]
{-46.28594 MeV}		(1+)
Cesium-11311355Cs58112.944428(9) u
[112.9142581 u]
{-51.76498 MeV}		(3/2+)
Cesium-11411455Cs59113.94130(8) u
[113.9111301 u]
{-54.6787 MeV}		(1+)114Ba
Cesium-11511555Cs60114.93591(11) u
[114.9057401 u]
{-59.69945 MeV}		(9/2+)115Ba
Cesium-11611655Cs61159.3339(11) u
[159.3037301 u]
{40365.26785 MeV}		(1+)116Ba
Cesium-116m116m55Cs61159.3339(11) u
[159.3037301 u]
{40365.26785 MeV}		4+,5,6
Cesium-11711755Cs62116.92862(7) u
[116.8984501 u]
{-66.49004 MeV}		(9/2+)117Ba
Cesium-117m117m55Cs62116.92862(7) u
[116.8984501 u]
{-66.49004 MeV}		(3/2+)
Cesium-11811855Cs63117.926560(14) u
[117.8963901 u]
{-68.40892 MeV}		2118Ba
Cesium-118m118m55Cs63117.926560(14) u
[117.8963901 u]
{-68.40892 MeV}		(6,7,8)
Cesium-11911955Cs64118.922377(15) u
[118.8922071 u]
{-72.30536 MeV}		9/2+119Ba
Cesium-119m119m55Cs64118.922377(15) u
[118.8922071 u]
{-72.30536 MeV}		3/2(+)
Cesium-12012055Cs65119.920677(11) u
[119.8905071 u]
{-73.8889 MeV}		2(+)120Ba
Cesium-120m120m55Cs65119.920677(11) u
[119.8905071 u]
{-73.8889 MeV}		(7-)
Cesium-12112155Cs66120.917227(15) u
[120.8870571 u]
{-77.10255 MeV}		(3/2)+121Ba
Cesium-121m121m55Cs66120.917227(15) u
[120.8870571 u]
{-77.10255 MeV}		9/2(+)
Cesium-12212255Cs67121.91611(4) u
[121.8859401 u]
{-78.14303 MeV}		1+122Ba
Cesium-122m1122m155Cs67121.91611(4) u
[121.8859401 u]
{-78.14303 MeV}		(3)+
Cesium-122m2122m255Cs67121.91611(4) u
[121.8859401 u]
{-78.14303 MeV}		8(-)
Cesium-122m3122m355Cs67121.91611(4) u
[121.8859401 u]
{-78.14303 MeV}		(5)-
Cesium-12312355Cs68122.912996(13) u
[122.8828261 u]
{-81.0437 MeV}		1/2+123Ba
Cesium-123m1123m155Cs68122.912996(13) u
[122.8828261 u]
{-81.0437 MeV}		(11/2)-
Cesium-123m2123m255Cs68122.912996(13) u
[122.8828261 u]
{-81.0437 MeV}		(9/2+)
Cesium-12412455Cs69123.912258(9) u
[123.8820881 u]
{-81.73115 MeV}		1+124Ba
Cesium-124m124m55Cs69123.912258(9) u
[123.8820881 u]
{-81.73115 MeV}		(7)+
Cesium-12512555Cs70124.909728(8) u
[124.8795581 u]
{-84.08783 MeV}		1/2(+)125Ba
Cesium-125m125m55Cs70124.909728(8) u
[124.8795581 u]
{-84.08783 MeV}		(11/2-)
Cesium-12612655Cs71125.909446(11) u
[125.8792761 u]
{-84.35051 MeV}		1+126Ba
Cesium-126m1126m155Cs71125.909446(11) u
[125.8792761 u]
{-84.35051 MeV}
Cesium-126m2126m255Cs71125.909446(11) u
[125.8792761 u]
{-84.35051 MeV}
Cesium-12712755Cs72126.907417(6) u
[126.8772471 u]
{-86.24051 MeV}		1/2+127Ba
Cesium-127m127m55Cs72126.907417(6) u
[126.8772471 u]
{-86.24051 MeV}		(11/2)-
Cesium-12812855Cs73127.907749(6) u
[127.8775791 u]
{-85.93125 MeV}		1+128Ba
Cesium-12912955Cs74128.906066(5) u
[128.8758961 u]
{-87.49896 MeV}		1/2+129Ba
Cesium-13013055Cs75129.906709(9) u
[129.8765391 u]
{-86.90001 MeV}		1+
Cesium-130m130m55Cs75129.906709(9) u
[129.8765391 u]
{-86.90001 MeV}		5-
Cesium-13113155Cs76130.905465(5) u
[130.8752951 u]
{-88.05879 MeV}		5/2+131Ba
Cesium-13213255Cs77131.9064377(11) u
[131.8762678 u]
{-87.15272 MeV}		2+
Cesium-13313355Cs78132.90545196(6) u
[132.8752821 u]
{-88.07093 MeV}		7/2+133Ba
133Xe
Cesium-13413455Cs79133.906718503(17) u
[133.8765486 u]
{-86.89115 MeV}		4+134Ba
134Xe
Cesium-134m134m55Cs79133.906718503(17) u
[133.8765486 u]
{-86.89115 MeV}		8-
Cesium-13513555Cs80134.9059772(11) u
[134.8758073 u]
{-87.58167 MeV}		7/2+135Xe
Cesium-135m135m55Cs80134.9059772(11) u
[134.8758073 u]
{-87.58167 MeV}		19/2-
Cesium-13613655Cs81135.9073116(20) u
[135.8771417 u]
{-86.33869 MeV}		5+
Cesium-136m136m55Cs81135.9073116(20) u
[135.8771417 u]
{-86.33869 MeV}		8-
Cesium-13713755Cs82136.9070893(3) u
[136.8769194 u]
{-86.54576 MeV}		7/2+137Xe
252Cf
Cesium-13813855Cs83137.911017(10) u
[137.8808471 u]
{-82.88713 MeV}		3-138Xe
Cesium-138m1138m155Cs83137.911017(10) u
[137.8808471 u]
{-82.88713 MeV}		6-
Cesium-13913955Cs84138.913364(3) u
[138.8831941 u]
{-80.70091 MeV}		7/2+139Xe
Cesium-14014055Cs85139.917283(9) u
[139.8871131 u]
{-77.05039 MeV}		1-140Xe
Cesium-14114155Cs86140.920045(10) u
[140.8898751 u]
{-74.4776 MeV}		7/2+141Xe
Cesium-14214255Cs87141.924300(8) u
[141.8941301 u]
{-70.5141 MeV}		0-142Xe
Cesium-14314355Cs88142.927347(8) u
[142.8971771 u]
{-67.67583 MeV}		3/2+143Xe
Cesium-14414455Cs89143.932075(22) u
[143.9019051 u]
{-63.27173 MeV}		1(-)144Xe
Cesium-144m144m55Cs89143.932075(22) u
[143.9019051 u]
{-63.27173 MeV}		(>3)
Cesium-14514555Cs90144.935529(10) u
[144.9053591 u]
{-60.05435 MeV}		3/2+145Xe
144Xe
Cesium-14614655Cs91145.940622(3) u
[145.9104521 u]
{-55.31025 MeV}		1-146Xe
Cesium-14714755Cs92146.944262(9) u
[146.9140921 u]
{-51.91961 MeV}		(3/2+)147Xe
Cesium-14814855Cs93147.949639(14) u
[147.9194691 u]
{-46.91097 MeV}
Cesium-14914955Cs94148.95357(43) u
[148.9234001 u]
{-43.24927 MeV}
Cesium-15015055Cs95149.95902(43) u
[149.9288501 u]
{-38.17262 MeV}
Cesium-15115155Cs96150.96325(54) u
[150.9330801 u]
{-34.2324 MeV}

 

Radioactive Decay Properties

IsotopeRadioactive DecayExtern
Half-lifeDecay ModeProbabilityEnergy
789101112
Cs-1120.49(3) msp → 111Xe
α → 108I		> 97.4 %
< 0.26 %
3.93(12) MeV		AL
Cs-11317.7(4) μsp → 112Xe100 %AL
Cs-1140.57(2) sEC/β+ → 114Xe
EC, p → 113I
EC, α → 110Te
α → 110I		99.982(6) %
8.7(13) %
0.19(3) %
0.018(6) %		12.40(7) MeV


3.36(5) MeV		AL
Cs-1151.4(8) sEC/β+ → 115Xe
β+, p → 114I		99.93 %
0.07 %		8.96(10) MeV
AL
Cs-1160.70(4) sEC/β+ → 116Xe
EC, p → 115I
EC, α → 112Te		97.1 %
2.8(7) %
0.049(25) %		11.0(1) MeV

AL
Cs-116m3.85(13) sβ+ → 116Xe
β+, p → 115I
EC, α → 112Te		99.5 %
0.51(15) %
0.008(2) %

AL
Cs-1178.4(6) sEC/β+ → 117Xe100 %7.69(6) MeVAL
Cs-117m6.5(4) sEC/β+ → 117Xe?AL
Cs-11814(2) sEC/β+ → 118Xe
EC, p → 117I
EC, α → 114Te		99.95 %
0.042 %
0.0024 %		9.670(16) MeV

AL
Cs-118m17(3) sβ+ → 118Xe
β+, p → 117I
EC, α → 114Te		99.95 %
0.042 %
0.0024 %

AL
Cs-11943.0(2) sEC/β+ → 119Xe100 %6.489(17) MeVAL
Cs-119m30.4(1) sEC/β+ → 119Xe100 %AL
Cs-12061.3(11) sβ+ → 120Xe
β+, p → 118I
β+, α → 116Te		< 100 %
<< 1%
<<		8.284(15) MeV

AL
Cs-120m57(6) sEC/β+ → 120Xe100 %AL
Cs-121155(4) sβ+ → 121Xe100 %5.379(18) MeVAL
Cs-121m122(3) sβ+ → 121Xe
Iso → 121Cs		83 %
17 %
AL
Cs-12221.18(19) sEC/β+ → 122Xe100 %7.21(4) MeVAL
Cs-122m11 μsAL
Cs-122m23.70(11) minEC/β+ → 122Xe100 %AL
Cs-122m30.36(2) sIso → 122Cs100 %AL
Cs-1235.88(3) minEC/β+ → 123Xe100 %4.205(15) MeVAL
Cs-123m11.64(12) sIso → 123Cs100 %AL
Cs-123m2114(5) nsAL
Cs-12430.9(4) sEC/β+ → 124Xe100 %5.93(8) MeVAL
Cs-124m6.3(2) sIso → 124Cs100 %AL
Cs-12546.7(1) minEC/β+ → 125Xe100 %3.105(8) MeVAL
Cs-125m0.90(3) msIso → 125Cs100 %AL
Cs-1261.64(2) minEC/β+ → 126Xe100 %4.796(11) MeVAL
Cs-126m11 μsAL
Cs-126m2171(14) μsAL
Cs-1276.25(10) hEC/β+ → 127Xe100 %2.081(7) MeVAL
Cs-127m55(3) μsIso → 127Cs100 %AL
Cs-1283.640(14) minEC/β+ → 128Xe100 %3.929(6) MeVAL
Cs-12932.06(6) hEC/β+ → 129Xe100 %1.197(5) MeVAL
Cs-13029.21(4) minEC/β+ → 130Xe
β- → 130Ba		98.4 %
1.6 %		2.981(8) MeV
0.362(9) MeV		AL
Cs-130m3.46(6) minIso → 130Cs
β+ → 130Xe		99.83 %
0.16 %
AL
Cs-1319.689(16) dEC → 131Xe100 %0.355(5) MeVAL
Cs-1326.480(6) dEC/β+ → 132Xe
β- → 132Ba		98.13(9) %
1.87(9) %		2.1263(10) MeV
1.2823(15) MeV		AL
Cs-133stableAL
Cs-1342.0652(4) aβ- → 134Ba
EC → 134Xe		99.9997(1) %
0.0003(1) %		2.0587(3) MeV
1.234668(18) MeV		AL
Cs-134m2.912(2) hIso → 134Cs100 %AL
Cs-1352.3(3) × 106 aβ- → 135Ba100 %2.689(10) MeVAL
Cs-135m53(2) minIso → 135Cs100 %AL
Cs-13613.01(5) dβ- → 136Ba100 %2.5482(19) MeVAL
Cs-136m17.5(2) sβ- → 136Ba
Iso → 136Cs		?
?
AL
Cs-13730.08(9) aβ- → 137Ba100 %1.17563(17) MeVAL
Cs-13832.5(2) minβ- → 138Ba100 %5.375(9) MeVAL
Cs-138m12.91(8) minβ- → 138Ba
Iso → 138Cs		19(2) %
81(2) %
AL
Cs-1399.27(5) minβ- → 139Ba100 %4.213(3) MeVAL
Cs-14063.7(3) sβ- → 140Ba100 %6.219(10) MeVAL
Cs-14124.84(16) sβ- → 141Ba
β-, n → 140Ba		99.96 %
0.035(3) %		5.255(10) MeV
0.721(12) MeV		AL
Cs-1421.684(14) sβ- → 142Ba
β-, n → 141Ba		99.9 %
0.090(4) %		7.328(8) MeV
1.147(9) MeV		AL
Cs-1431.791(7) sβ- → 143Ba
β-, n → 142Ba		98.36 %
1.64(7) %		6.262(10) MeV
2.095(10) MeV		AL
Cs-144994(6) msβ- → 144Ba
β-, n → 143Ba		96.97 %
3.03(13) %		8.496(20) MeV
2.595(21) MeV		AL
Cs-144m< 1 sβ- → 144Ba?AL
Cs-145587(5) msβ- → 145Ba
β-, n → 144Ba		85.3 %
14.7(9) %		7.462(12) MeV
3.641(11) MeV		AL
Cs-146322.0(13) msβ- → 146Ba
β-, n → 145Ba		85.8 %
14.2(5) %		9.637(21) MeV
4.134(9) MeV		AL
Cs-147230(1) msβ- → 147Ba
β-, n → 146Ba		71.5 %
28.5(17) %		8.344(21) MeV
4.956(22) MeV		AL
Cs-148146(6) msβ- → 148Ba
β-, n → 147Ba		74.9 %
25.1(25) %		10.68(6) MeV
5.282(24) MeV		AL
Cs-149113(8) msβ- → 149Ba
β-, n → 148Ba		100 %
?		9.87(59) MeV
6.27(40) MeV		AL
Cs-15084(8) msβ- → 150Ba
β-, n → 149Ba		80 %
20(10)		11.73(50) MeV
6.88(59) MeV		AL
Cs-15169(26) msβ- → 151Ba
β-, n → 150Ba		100 %
?		10.71(64) MeV
7.60(58) MeV		AL

 

Notes (related to the columns):

1 - name of the nuclide, isotope.
2 - E: isotope symbol with mass number (superscript; number of nucleons) and Atomic number (subscript; number of protons).
3 - N: number of neutrons.
4 - relative atomic mass of the Cesium isotope (isotopic mass including electrons) and the mass of the atomic nucleus in square brackets (nuclear mass, nuclide mass without electrons), each related to 12C = 12.00000 [2]. In addition, the mass excess is given in MeV.
5 - nuclear spin I, unit: h/2π.
6 - source nuclides: Possible, assumed or actual source nuclides (mother nuclides, parent nuclides). If applicable, the corresponding decay modes can be found in the data for the respective starting nuclide.

7 - isotope notation in short form.
8 - decay: half-live of the Cesium isotope (a = years; ; d = days; h = hours; min = minutes; s = seconds).
9 - decay mode: type of decay into the respective daughter nuclides with n = neutron emission; p = proton emission; α = alpha decay; β- = beta minus decay with electron emission; EC = electron capture; β+ = positron emission; ε = β+ and/or EC; Iso = isomeric transition; CD = cluster decay; SF = spontaneous decay.
10 - decay probability in percent (%).
11 - decay energy; Particle energy related to decay type.
12 - other information and notes: AL = Adopted Levels (link to external data [1]).

Miscellaneous:

()- Numbers in brackets: uncertainty to represent the spread of the reported value.
~ - Theoretical values or systematic trends.
  - unlisted-: Nuclides that have already been mentioned in the literature but for some reason can no longer be found in the current nuclide tables because their discovery e.g. has not confirmed.

 

NMR active Cesium nuclides

Nuclide
quantity 1)
spin		Nuclear
magnetic
moment
μ/μN		Gyromagnetic ratio
{Quadrupole moment}		Resonant
frequency
v0 bei 1 T		Relative
sensitivity
H0 = const.
v0 = const. 3)
133Cs
100 %
7/2+		+2,5778(14)3,5339
{- 0,00343(10)}		5,62340,04838
2,7736

1) Quantity Percentage of natural occurrence.

2) Gyromagnetic ratio: 107 rad T-1 s-1
    Quadrupole moment: Q [barn] = [100 fm2]

3) Related to 1H = 1,000.

 

Radiation Protection

According to the Radiation Protection Ordinance (StrlSchV 2018, Germany), the following values (columns 1 to 7) apply to the handling of Cesium radionuclides:

NuclideLimit ValueHASS limitSCDaughter NuclidesHalf-life
Cs-125104 Bq10 Bq/g46.7 min
Cs-127105 Bq100 Bq/g6.3 h
Cs-129105 Bq10 Bq/g10 Bq cm-232.2 h
Cs-130106 Bq100 Bq/g29.2 min
Cs-131106 Bq1000 Bq/g20 TBq100 Bq cm-29.7 d
Cs-132105 Bq10 Bq/g1 Bq cm-26.5 d
Cs-134104 Bq0,1 Bq/g1 Bq cm-22.1 a
Cs-134m105 Bq1000 Bq/g100 Bq cm-22.9 h
Cs-135107 Bq100 Bq/g100 Bq cm-22.3 × 106 a
Cs-136105 Bq1 Bq/g0,03 TBq1 Bq cm-213.0 d
Cs-137+104 Bq0,1 Bq/g0,1 TBq1 Bq cm-2Ba-137m30.2 a
Cs-138104 Bq10 Bq/g1 Bq cm-233.4 min

(HASS = High-Activity Sealed Radioactive Sources; SC = surface contamination)

 

Literature Sources and References

Properties of the Cesium nucleides

[1] - NuDat: National Nuclear Data Center, Brookhaven National Laboratory, based on ENSDF and the Nuclear Wallet Cards.

[2] - G. Audi et. al.: The NUBASE evaluation of nuclear and decay properties. Nuclear Physics, (2003), DOI 10.1016/j.nuclphysa.2003.11.001.

[3] - Live Chart of Nuclides. Nuclear structure and decay data.

Cesium: NMR properties - 133Cs-NMR

[4] - N. J. Stone: Table of nuclear magnetic dipole and electric quadrupole moments. Atomic Data and Nuclear Data Tables, (2005), DOI 10.1016/j.adt.2005.04.001.

[5] - Pekka Pyykkö: Year-2008 nuclear quadrupole moments. Molecular Physics, (2008), DOI 10.1080/00268970802018367.

[6] - Pekka Pyykkö: Year-2017 nuclear quadrupole moments. Molecular Physics, (2018), DOI 10.1080/00268976.2018.1426131.

[7] - N. J. Stone: Table of recommended nuclear magnetic dipole moments. IAEA, (2019).

More sources:

[8] - Isotopic abundances, atomic weights and isotopic masses: see respective keyword.

 

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