Isotopes of caesium
Encyclopedia
Caesium
(Cs) has 40 known isotope
s. The atomic mass
es of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 2.3 million years, 137Cs with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.
Beginning in 1945 with the commencement of nuclear testing
, caesium isotopes were released into the atmosphere
where it is absorbed readily into solution and is returned to the surface of the earth as a component of radioactive fallout. Once caesium enters the ground water, it is deposited on soil surfaces and removed from the landscape primarily by particle transport. As a result, the input function of these isotopes can be estimated as a function of time.
Standard atomic mass: 132.9054519(2) u
of caesium. It is also produced by nuclear fission
in nuclear reactors. One specific quantum transition in the Caesium-133 atom is used to define the second
, a unit of time.
of 2.0652 years. It is produced both directly (at a very small yield because 134Xe is stable) as a fission product
and via neutron capture
from nonradioactive Cs-133 (neutron capture cross section
29 barns
), which is a common fission product. Caesium 134 is not produced via beta decay
of other fission product nuclides of mass 134 since beta decay stops at stable 134Xe. It is also not produced by nuclear weapons because 133Cs is created by beta decay of original fission products only long after the nuclear explosion is over.
The combined yield of 133Cs and 134Cs is given as 6.7896%. The proportion between the two will change with continued neutron irradiation. 134Cs also captures neutrons with a cross section of 140 barns, becoming long-lived radioactive 135Cs.
s and the only alkaline one. In nuclear reprocessing
, it stays with Cs-137 and other medium-lived fission products rather than with other long-lived fission products. The low decay energy
, lack of gamma radiation, and long half-life of 135Cs make this isotope much less hazardous than 137Cs
or 134Cs.
Its precursor 135Xe
has a high fission product yield
(e.g. 6.3333% for 235U
and thermal neutrons) but also has the highest known thermal neutron neutron capture cross section of any nuclide. Because of this, much of the 135Xe produced in current thermal reactor
s (as much as >90% at steady-state full power) will be converted to stable 136Xe before it can decay to 135Cs. Little or no 135Xe will be destroyed by neutron capture after a reactor shutdown, or in a molten salt reactor
that continuously removes xenon from its fuel, a fast neutron reactor
, or a nuclear weapon.
A nuclear reactor will also produce much smaller amounts of 135Cs from the nonradioactive fission product Cs-133 by successive neutron capture to 134Cs and then 135Cs.
The thermal neutron capture cross section and resonance integral of 135Cs are and respectively. Disposal of Cs-135 by nuclear transmutation
is difficult, because of the low cross section as well as because neutron irradiation of mixed-isotope fission caesium produces more Cs-135 from stable Cs-133. In addition, the intense medium-term radioactivity of Cs-137 makes handling of nuclear waste difficult.
, which are responsible for most of the radioactivity of spent nuclear fuel
after several years of cooling, up to several hundred years after use. It constitutes most of the radioactivity still left from the Chernobyl accident. 137Cs beta decays to barium-137m (a short-lived nuclear isomer
) then to nonradioactive barium-137, and is also a strong emitter of gamma radiation. 137Cs has a very low rate of neutron capture and cannot be feasibly disposed of in this way, but must be allowed to decay. 137Cs has been used as a tracer
in hydrologic studies, analogous to the use of 3H
.
Almost all caesium produced from nuclear fission comes from beta decay of originally more neutron-rich fission products, passing through isotopes of iodine
then isotopes of xenon
. Because these elements are volatile and can diffuse through nuclear fuel or air, caesium is often created far from the original site of fission.
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
(Cs) has 40 known isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s. The atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....
es of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 2.3 million years, 137Cs with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.
Beginning in 1945 with the commencement of nuclear testing
Nuclear testing
Nuclear weapons tests are experiments carried out to determine the effectiveness, yield and explosive capability of nuclear weapons. Throughout the twentieth century, most nations that have developed nuclear weapons have tested them...
, caesium isotopes were released into the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
where it is absorbed readily into solution and is returned to the surface of the earth as a component of radioactive fallout. Once caesium enters the ground water, it is deposited on soil surfaces and removed from the landscape primarily by particle transport. As a result, the input function of these isotopes can be estimated as a function of time.
Standard atomic mass: 132.9054519(2) u
Caesium-133
Caesium-133 is the only naturally occurring and only stable isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of caesium. It is also produced by nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
in nuclear reactors. One specific quantum transition in the Caesium-133 atom is used to define the second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
, a unit of time.
Caesium-134
Caesium-134 has a half-lifeHalf-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 2.0652 years. It is produced both directly (at a very small yield because 134Xe is stable) as a fission product
Fission product
Nuclear fission products are the atomic fragments left after a large atomic nucleus fissions. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat , gamma rays and neutrinos. The...
and via neutron capture
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...
from nonradioactive Cs-133 (neutron capture cross section
Neutron cross-section
In nuclear and particle physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. In conjunction with the neutron flux, it enables the calculation of the reaction rate, for example to derive the thermal power...
29 barns
Barn (unit)
A barn is a unit of area. Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is used in all fields of high energy physics to express the cross sections of any scattering process, and is best understood as a measure of the...
), which is a common fission product. Caesium 134 is not produced via beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
of other fission product nuclides of mass 134 since beta decay stops at stable 134Xe. It is also not produced by nuclear weapons because 133Cs is created by beta decay of original fission products only long after the nuclear explosion is over.
The combined yield of 133Cs and 134Cs is given as 6.7896%. The proportion between the two will change with continued neutron irradiation. 134Cs also captures neutrons with a cross section of 140 barns, becoming long-lived radioactive 135Cs.
Caesium-135
Caesium-135 is a mildly radioactive isotope of caesium, undergoing low-energy beta decay to barium-135 with a half-life of 2.3 million years. It is one of the 7 long-lived fission productLong-lived fission product
Long-lived fission products are radioactive materials with a long half-life produced by nuclear fission.-Evolution of radioactivity in nuclear waste:...
s and the only alkaline one. In nuclear reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
, it stays with Cs-137 and other medium-lived fission products rather than with other long-lived fission products. The low decay energy
Decay energy
The decay energy is the energy released by a radioactive decay. Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation...
, lack of gamma radiation, and long half-life of 135Cs make this isotope much less hazardous than 137Cs
Caesium-137
Caesium-137 is a radioactive isotope of caesium which is formed as a fission product by nuclear fission.It has a half-life of about 30.17 years, and decays by beta emission to a metastable nuclear isomer of barium-137: barium-137m . Caesium-137 is a radioactive isotope of caesium which is formed...
or 134Cs.
Its precursor 135Xe
Xenon-135
Xenon-135 is an unstable isotope of xenon with a half-life of about 9.2 hours. 135Xe is a fission product of uranium and Xe-135 is the most powerful known neutron-absorbing nuclear poison , with a significant effect on nuclear reactor operation...
has a high fission product yield
Fission product yield
Nuclear fission splits a heavy nucleus such as uranium or plutonium into two lighter nuclei, which are called fission products. Yield refers to the fraction of a fission product produced per fission.Yield can be broken down by:#Individual isotope...
(e.g. 6.3333% for 235U
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
and thermal neutrons) but also has the highest known thermal neutron neutron capture cross section of any nuclide. Because of this, much of the 135Xe produced in current thermal reactor
Thermal reactor
A thermal reactor is a nuclear reactor that uses slow or thermal neutrons. Most power reactors are of this type. These type of reactors use a neutron moderator to slow neutrons until they approach the average kinetic energy of the surrounding particles, that is, to reduce the speed of the neutrons...
s (as much as >90% at steady-state full power) will be converted to stable 136Xe before it can decay to 135Cs. Little or no 135Xe will be destroyed by neutron capture after a reactor shutdown, or in a molten salt reactor
Molten salt reactor
A molten salt reactor is a type of nuclear fission reactor in which the primary coolant, or even the fuel itself is a molten salt mixture...
that continuously removes xenon from its fuel, a fast neutron reactor
Fast neutron reactor
A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons...
, or a nuclear weapon.
A nuclear reactor will also produce much smaller amounts of 135Cs from the nonradioactive fission product Cs-133 by successive neutron capture to 134Cs and then 135Cs.
The thermal neutron capture cross section and resonance integral of 135Cs are and respectively. Disposal of Cs-135 by nuclear transmutation
Nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...
is difficult, because of the low cross section as well as because neutron irradiation of mixed-isotope fission caesium produces more Cs-135 from stable Cs-133. In addition, the intense medium-term radioactivity of Cs-137 makes handling of nuclear waste difficult.
Caesium-137
137Cs with a half-life of 30.17 years is one of the two principal medium-lived fission products, along with 90SrStrontium-90
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
, which are responsible for most of the radioactivity of spent nuclear fuel
Spent nuclear fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor...
after several years of cooling, up to several hundred years after use. It constitutes most of the radioactivity still left from the Chernobyl accident. 137Cs beta decays to barium-137m (a short-lived nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
) then to nonradioactive barium-137, and is also a strong emitter of gamma radiation. 137Cs has a very low rate of neutron capture and cannot be feasibly disposed of in this way, but must be allowed to decay. 137Cs has been used as a tracer
Tracer
Tracer may refer to:* Histochemical tracer, a substance used for tracing purposes in histochemistry, the study of the composition of cells and tissues...
in hydrologic studies, analogous to the use of 3H
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
.
Other isotopes of caesium
The other isotopes have half-lives from a few days to fractions of a second.Almost all caesium produced from nuclear fission comes from beta decay of originally more neutron-rich fission products, passing through isotopes of iodine
Isotopes of iodine
There are 37 known isotopes of iodine and only one, 127I, is stable. Iodine is thus a monoisotopic element.Its longest-lived radioactive isotope, 129I, has a half-life of 15.7 million years, which is far too short for it to exist as a primordial nuclide...
then isotopes of xenon
Isotopes of xenon
Naturally occurring xenon is made of nine stable isotopes. Xenon has the second highest number of stable isotopes. Only tin, with 10 stable isotopes, has more...
. Because these elements are volatile and can diffuse through nuclear fuel or air, caesium is often created far from the original site of fission.
Table
| nuclide Nuclide A nuclide is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state.... symbol |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-life | decay mode(s)Abbreviations: EC: Electron capture Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... |
daughter isotope(s)Bold for stable isotopes, bold italics for near-stable isotopes (half-life longer than the age of the universe Age of the universe The age of the universe is the time elapsed since the Big Bang posited by the most widely accepted scientific model of cosmology. The best current estimate of the age of the universe is 13.75 ± 0.13 billion years within the Lambda-CDM concordance model... ) |
nuclear spin Spin (physics) In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,... |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation Excited state Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state.... energy |
|||||||||
| 112Cs | 55 | 57 | 111.95030(33)# | 500(100) µs | p Proton emission Proton emission is a type of radioactive decay in which a proton is ejected from a nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state of very... |
111Xe | 1+# | ||
| α Alpha decay Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less... |
108I | ||||||||
| 113Cs | 55 | 58 | 112.94449(11) | 16.7(7) µs | p (99.97%) | 112Xe | 5/2+# | ||
| β+ Beta decay In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a... (.03%) |
113Xe | ||||||||
| 114Cs | 55 | 59 | 113.94145(33)# | 0.57(2) s | β+ (91.09%) | 114Xe | (1+) | ||
| β+, p (8.69%) | 113I | ||||||||
| β+, α (.19%) | 110Te | ||||||||
| α (.018%) | 110I | ||||||||
| 115Cs | 55 | 60 | 114.93591(32)# | 1.4(8) s | β+ (99.93%) | 115Xe | 9/2+# | ||
| β+, p (.07%) | 114I | ||||||||
| 116Cs | 55 | 61 | 115.93337(11)# | 0.70(4) s | β+ (99.67%) | 116Xe | (1+) | ||
| β+, p (.279%) | 115I | ||||||||
| β+, α (.049%) | 112Te | ||||||||
| 116mCs | 100(60)# keV | 3.85(13) s | β+ (99.48%) | 116Xe | 4+,5,6 | ||||
| β+, p (.51%) | 115I | ||||||||
| β+, α (.008%) | 112Te | ||||||||
| 117Cs | 55 | 62 | 116.92867(7) | 8.4(6) s | β+ | 117Xe | (9/2+)# | ||
| 117mCs | 150(80)# keV | 6.5(4) s | β+ | 117Xe | 3/2+# | ||||
| 118Cs | 55 | 63 | 117.926559(14) | 14(2) s | β+ (99.95%) | 118Xe | 2 | ||
| β+, p (.042%) | 117I | ||||||||
| β+, α (.0024%) | 114Te | ||||||||
| 118mCs | 100(60)# keV | 17(3) s | β+ (99.95%) | 118Xe | (7-) | ||||
| β+, p (.042%) | 117I | ||||||||
| β+, α (.0024%) | 114Te | ||||||||
| 119Cs | 55 | 64 | 118.922377(15) | 43.0(2) s | β+ | 119Xe | 9/2+ | ||
| β+, α (2×10−6%) | 115Te | ||||||||
| 119mCs | 50(30)# keV | 30.4(1) s | β+ | 119Xe | 3/2(+) | ||||
| 120Cs | 55 | 65 | 119.920677(11) | 61.2(18) s | β+ | 120Xe | 2(-#) | ||
| β+, α (2×10−5%) | 116Te | ||||||||
| β+, p (7×10−6%) | 118I | ||||||||
| 120mCs | 100(60)# keV | 57(6) s | β+ | 120Xe | (7-) | ||||
| β+, α (2×10−5%) | 116Te | ||||||||
| β+, p (7×10−6%) | 118I | ||||||||
| 121Cs | 55 | 66 | 120.917229(15) | 155(4) s | β+ | 121Xe | 3/2(+) | ||
| 121mCs | 68.5(3) keV | 122(3) s | β+ (83%) | 121Xe | 9/2(+) | ||||
| IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... (17%) |
121Cs | ||||||||
| 122Cs | 55 | 67 | 121.91611(3) | 21.18(19) s | β+ | 122Xe | 1+ | ||
| β+, α (2×10−7%) | 118Te | ||||||||
| 122m1Cs | 45.8 keV | >1 µs | (3)+ | ||||||
| 122m2Cs | 140(30) keV | 3.70(11) min | β+ | 122Xe | 8- | ||||
| 122m3Cs | 127.0(5) keV | 360(20) ms | (5)- | ||||||
| 123Cs | 55 | 68 | 122.912996(13) | 5.88(3) min | β+ | 123Xe | 1/2+ | ||
| 123m1Cs | 156.27(5) keV | 1.64(12) s | IT | 123Cs | (11/2)- | ||||
| 123m2Cs | 231.63+X keV | 114(5) ns | (9/2+) | ||||||
| 124Cs | 55 | 69 | 123.912258(9) | 30.9(4) s | β+ | 124Xe | 1+ | ||
| 124mCs | 462.55(17) keV | 6.3(2) s | IT | 124Cs | (7)+ | ||||
| 125Cs | 55 | 70 | 124.909728(8) | 46.7(1) min | β+ | 125Xe | 1/2(+) | ||
| 125mCs | 266.6(11) keV | 900(30) ms | (11/2-) | ||||||
| 126Cs | 55 | 71 | 125.909452(13) | 1.64(2) min | β+ | 126Xe | 1+ | ||
| 126m1Cs | 273.0(7) keV | >1 µs | |||||||
| 126m2Cs | 596.1(11) keV | 171(14) µs | |||||||
| 127Cs | 55 | 72 | 126.907418(6) | 6.25(10) h | β+ | 127Xe | 1/2+ | ||
| 127mCs | 452.23(21) keV | 55(3) µs | (11/2)- | ||||||
| 128Cs | 55 | 73 | 127.907749(6) | 3.640(14) min | β+ | 128Xe | 1+ | ||
| 129Cs | 55 | 74 | 128.906064(5) | 32.06(6) h | β+ | 129Xe | 1/2+ | ||
| 130Cs | 55 | 75 | 129.906709(9) | 29.21(4) min | β+ (98.4%) | 130Xe | 1+ | ||
| β- (1.6%) | 130Ba | ||||||||
| 130mCs | 163.25(11) keV | 3.46(6) min | IT (99.83%) | 130Cs | 5- | ||||
| β+ (.16%) | 130Xe | ||||||||
| 131Cs | 55 | 76 | 130.905464(5) | 9.689(16) d | EC Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... |
131Xe | 5/2+ | ||
| 132Cs | 55 | 77 | 131.9064343(20) | 6.480(6) d | β+ (98.13%) | 132Xe | 2+ | ||
| β- (1.87%) | 132Ba | ||||||||
| 133CsUsed to define the second Second The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock.... Fission product Fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus fissions. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat , gamma rays and neutrinos. The... |
55 | 78 | 132.905451933(24) | Observationally StableBelieved to be capable of spontaneous fission Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses... |
7/2+ | 1.0000 | |||
| 134Cs | 55 | 79 | 133.906718475(28) | 2.0652(4) a | β- | 134Ba | 4+ | ||
| EC (3×10−4%) | 134Xe | ||||||||
| 134mCs | 138.7441(26) keV | 2.912(2) h | IT | 134Cs | 8- | ||||
| 135Cs | 55 | 80 | 134.9059770(11) | 2.3(3)×106 a | β- | 135Ba | 7/2+ | ||
| 135mCs | 1632.9(15) keV | 53(2) min | IT | 135Cs | 19/2- | ||||
| 136Cs | 55 | 81 | 135.9073116(20) | 13.16(3) d | β- | 136Ba | 5+ | ||
| 136mCs | 518(5) keV | 19(2) s | β- | 136Ba | 8- | ||||
| IT | 136Cs | ||||||||
| 137Cs Caesium-137 Caesium-137 is a radioactive isotope of caesium which is formed as a fission product by nuclear fission.It has a half-life of about 30.17 years, and decays by beta emission to a metastable nuclear isomer of barium-137: barium-137m . Caesium-137 is a radioactive isotope of caesium which is formed... |
55 | 82 | 136.9070895(5) | 30.1671(13) a | β- (95%) | 137mBa | 7/2+ | ||
| β- (5%) | 137Ba | ||||||||
| 138Cs | 55 | 83 | 137.911017(10) | 33.41(18) min | β- | 138Ba | 3- | ||
| 138mCs | 79.9(3) keV | 2.91(8) min | IT (81%) | 138Cs | 6- | ||||
| β- (19%) | 138Ba | ||||||||
| 139Cs | 55 | 84 | 138.913364(3) | 9.27(5) min | β- | 139Ba | 7/2+ | ||
| 140Cs | 55 | 85 | 139.917282(9) | 63.7(3) s | β- | 140Ba | 1- | ||
| 141Cs | 55 | 86 | 140.920046(11) | 24.84(16) s | β- (99.96%) | 141Ba | 7/2+ | ||
| β-, n Neutron emission Neutron emission is a type of radioactive decay of atoms containing excess neutrons, in which a neutron is simply ejected from the nucleus. Two examples of isotopes which emit neutrons are helium-5 and beryllium-13... (.0349%) |
140Ba | ||||||||
| 142Cs | 55 | 87 | 141.924299(11) | 1.689(11) s | β- (99.9%) | 142Ba | 0- | ||
| β-, n (.091%) | 141Ba | ||||||||
| 143Cs | 55 | 88 | 142.927352(25) | 1.791(7) s | β- (98.38%) | 143Ba | 3/2+ | ||
| β-, n (1.62%) | 142Ba | ||||||||
| 144Cs | 55 | 89 | 143.932077(28) | 994(4) ms | β- (96.8%) | 144Ba | 1(-#) | ||
| β-, n (3.2%) | 143Ba | ||||||||
| 144mCs | 300(200)# keV | <1 s | β- | 144Ba | (>3) | ||||
| IT | 144Cs | ||||||||
| 145Cs | 55 | 90 | 144.935526(12) | 582(6) ms | β- (85.7%) | 145Ba | 3/2+ | ||
| β-, n (14.3%) | 144Ba | ||||||||
| 146Cs | 55 | 91 | 145.94029(8) | 0.321(2) s | β- (85.8%) | 146Ba | 1- | ||
| β-, n (14.2%) | 145Ba | ||||||||
| 147Cs | 55 | 92 | 146.94416(6) | 0.235(3) s | β- (71.5%) | 147Ba | (3/2+) | ||
| β-, n (28.49%) | 147Ba | ||||||||
| 148Cs | 55 | 93 | 147.94922(62) | 146(6) ms | β- (74.9%) | 148Ba | |||
| β-, n (25.1%) | 147Ba | ||||||||
| 149Cs | 55 | 94 | 148.95293(21)# | 150# ms [>50 ms] | β- | 149Ba | 3/2+# | ||
| β-, n | 148Ba | ||||||||
| 150Cs | 55 | 95 | 149.95817(32)# | 100# ms [>50 ms] | β- | 150Ba | |||
| β-, n | 149Ba | ||||||||
| 151Cs | 55 | 96 | 150.96219(54)# | 60# ms [>50 ms] | β- | 151Ba | 3/2+# | ||
| β-, n | 150Ba | ||||||||