Naturally occurring

xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

(₅₄Xe) consists of seven

stable A stable is a building in which livestock, especially horses, are kept. It most commonly means a building that is divided into separate stalls for individual animals and livestock. There are many different types of stables in use today; the ...

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

s and two very long-lived isotopes.

Double electron capture Double electron capture is a decay mode of an atomic nucleus. For a nuclide (''A'', ''Z'') with a number of nucleons ''A'' and atomic number ''Z'', double electron capture is only possible if the mass of the nuclide (''A'', ''Z''−2) is lower. I ...

has been observed in ¹²⁴Xe (half-life ) and double beta decay in ¹³⁶Xe (half-life ), which are among the longest measured half-lives of all nuclides. The isotopes ¹²⁶Xe and ¹³⁴Xe are also predicted to undergo double beta decay, but this has never been observed in these isotopes, so they are considered to be stable. Beyond these stable forms, 32 artificial

unstable isotope In numerous fields of study, the component of instability within a system is generally characterized by some of the outputs or internal states growing without bounds. Not all systems that are not stable are unstable; systems can also be mar ...

s and various isomers have been studied, the longest-lived of which is ¹²⁷Xe with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of 36.345 days. All other isotopes have half-lives less than 12 days, most less than 20 hours. The shortest-lived isotope, ¹⁰⁸Xe, has a half-life of 58 μs, and is the heaviest known nuclide with equal numbers of protons and neutrons. Of known isomers, the longest-lived is ^131mXe with a half-life of 11.934 days. ¹²⁹Xe is produced by

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...

of ¹²⁹I (

: 16 million years); ^131mXe, ¹³³Xe, ^133mXe, and ¹³⁵Xe are some of the

fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...

s of both ²³⁵U and ²³⁹Pu, so are used as indicators of

nuclear explosion A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, t ...

s. The artificial isotope ¹³⁵Xe is of considerable significance in the operation of nuclear fission reactors. ¹³⁵Xe has a huge

cross section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...

for

thermal neutron The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium with ...

s, 2.65×10⁶

barns A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Allen G. N ...

, so it acts as a neutron absorber or "

poison Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...

" that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the American

Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...

for

plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...

production. Because of this effect, designers must make provisions to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel) over the initial value needed to start the chain reaction. For the same reason, the fission products produced in a nuclear explosion and a power plant differ significantly as a large share of will absorb neutrons in a steady state reactor, while basically none of the will have had time to decay to Xenon before the explosion of the bomb removes it from the neutron radiation. Relatively high concentrations of radioactive xenon isotopes are also found emanating from nuclear reactors due to the release of this fission gas from cracked fuel rods or fissioning of uranium in cooling water. The concentrations of these isotopes are still usually low compared to the naturally occurring radioactive noble gas ²²²Rn. Because xenon is a

tracer Tracer may refer to: Science * Flow tracer, any fluid property used to track fluid motion * Fluorescent tracer, a substance such as 2-NBDG containing a fluorophore that is used for tracking purposes * Histochemical tracer, a substance used for tr ...

for two

parent isotope In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay directly ...

s, Xe isotope ratios in

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

s are a powerful tool for studying the

formation of the solar system The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a ...

. The I-Xe method of dating gives the time elapsed between nucleosynthesis and the condensation of a solid object from the

solar nebula The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a ...

(xenon being a gas, only that part of it that formed after condensation will be present inside the object). Xenon isotopes are also a powerful tool for understanding terrestrial differentiation. Excess ¹²⁹Xe found in

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

well gases from

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

was believed to be from the decay of

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

-derived gases soon after Earth's formation. It has been suggested that the isotopic composition of atmospheric xenon fluctuated prior to the GOE before stabilizing, perhaps as a result of the rise in atmospheric O₂.

List of isotopes

, - , ¹⁰⁸Xe , style="text-align:right" , 54 , style="text-align:right" , 54 , , 58(+106−23) μs , α , ¹⁰⁴Te , 0+ , , , - , ¹⁰⁹Xe , style="text-align:right" , 54 , style="text-align:right" , 55 , , 13(2) ms , α , ¹⁰⁵Te , , , , - , rowspan=2, ¹¹⁰Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 56 , rowspan=2, 109.94428(14) , rowspan=2, 310(190) ms
05(+35−25) ms, β⁺ , ¹¹⁰I , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , α , ¹⁰⁶Te , - , rowspan=2, ¹¹¹Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 57 , rowspan=2, 110.94160(33)# , rowspan=2, 740(200) ms , β⁺ (90%) , ¹¹¹I , rowspan=2, 5/2+# , rowspan=2, , rowspan=2, , - , α (10%) , ¹⁰⁷Te , - , rowspan=2, ¹¹²Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 58 , rowspan=2, 111.93562(11) , rowspan=2, 2.7(8) s , β⁺ (99.1%) , ¹¹²I , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , α (.9%) , ¹⁰⁸Te , - , rowspan=4, ¹¹³Xe , rowspan=4 style="text-align:right" , 54 , rowspan=4 style="text-align:right" , 59 , rowspan=4, 112.93334(9) , rowspan=4, 2.74(8) s , β⁺ (92.98%) , ¹¹³I , rowspan=4, (5/2+)# , rowspan=4, , rowspan=4, , - , β⁺, p (7%) , ¹¹²Te , - , α (.011%) , ¹⁰⁹Te , - , β⁺, α (.007%) , ¹⁰⁹Sb , - , ¹¹⁴Xe , style="text-align:right" , 54 , style="text-align:right" , 60 , 113.927980(12) , 10.0(4) s , β⁺ , ¹¹⁴I , 0+ , , , - , rowspan=3, ¹¹⁵Xe , rowspan=3 style="text-align:right" , 54 , rowspan=3 style="text-align:right" , 61 , rowspan=3, 114.926294(13) , rowspan=3, 18(4) s , β⁺ (99.65%) , ¹¹⁵I , rowspan=3, (5/2+) , rowspan=3, , rowspan=3, , - , β⁺, p (.34%) , ¹¹⁴Te , - , β⁺, α (3×10⁻⁴%) , ¹¹¹Sb , - , ¹¹⁶Xe , style="text-align:right" , 54 , style="text-align:right" , 62 , 115.921581(14) , 59(2) s , β⁺ , ¹¹⁶I , 0+ , , , - , rowspan=2, ¹¹⁷Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 63 , rowspan=2, 116.920359(11) , rowspan=2, 61(2) s , β⁺ (99.99%) , ¹¹⁷I , rowspan=2, 5/2(+) , rowspan=2, , rowspan=2, , - , β⁺, p (.0029%) , ¹¹⁶Te , - , ¹¹⁸Xe , style="text-align:right" , 54 , style="text-align:right" , 64 , 117.916179(11) , 3.8(9) min , β⁺ , ¹¹⁸I , 0+ , , , - , ¹¹⁹Xe , style="text-align:right" , 54 , style="text-align:right" , 65 , 118.915411(11) , 5.8(3) min , β⁺ , ¹¹⁹I , 5/2(+) , , , - , ¹²⁰Xe , style="text-align:right" , 54 , style="text-align:right" , 66 , 119.911784(13) , 40(1) min , β⁺ , ¹²⁰I , 0+ , , , - , ¹²¹Xe , style="text-align:right" , 54 , style="text-align:right" , 67 , 120.911462(12) , 40.1(20) min , β⁺ , ¹²¹I , (5/2+) , , , - , ¹²²Xe , style="text-align:right" , 54 , style="text-align:right" , 68 , 121.908368(12) , 20.1(1) h , β⁺ , ¹²²I , 0+ , , , - , ¹²³Xe , style="text-align:right" , 54 , style="text-align:right" , 69 , 122.908482(10) , 2.08(2) h , EC , ¹²³I , 1/2+ , , , - , style="text-indent:1em" , ^123mXe , colspan="3" style="text-indent:2em" , 185.18(22) keV , 5.49(26) μs , , , 7/2(−) , , , - , ¹²⁴Xe Primordial

radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...

, style="text-align:right" , 54 , style="text-align:right" , 70 , 123.905893(2) , 1.8(0.5 (stat), 0.1 (sys)) y , Double EC , ¹²⁴Te , 0+ , 9.52(3)×10⁻⁴ , , - , ¹²⁵Xe , style="text-align:right" , 54 , style="text-align:right" , 71 , 124.9063955(20) , 16.9(2) h , β⁺ , ¹²⁵I , 1/2(+) , , , - , style="text-indent:1em" , ^125m1Xe , colspan="3" style="text-indent:2em" , 252.60(14) keV , 56.9(9) s , IT , ¹²⁵Xe , 9/2(−) , , , - , style="text-indent:1em" , ^125m2Xe , colspan="3" style="text-indent:2em" , 295.86(15) keV , 0.14(3) μs , , , 7/2(+) , , , - , ¹²⁶Xe , style="text-align:right" , 54 , style="text-align:right" , 72 , 125.904274(7) , colspan=3 align=center, Observationally StableSuspected of undergoing β⁺β⁺ decay to ¹²⁶Te , 0+ , 8.90(2)×10⁻⁴ , , - , ¹²⁷Xe , style="text-align:right" , 54 , style="text-align:right" , 73 , 126.905184(4) , 36.345(3) d , EC , ¹²⁷I , 1/2+ , , , - , style="text-indent:1em" , ^127mXe , colspan="3" style="text-indent:2em" , 297.10(8) keV , 69.2(9) s , IT , ¹²⁷Xe , 9/2− , , , - , ¹²⁸Xe , style="text-align:right" , 54 , style="text-align:right" , 74 , 127.9035313(15) , colspan=3 align=center, StableTheoretically capable of

spontaneous fission Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdo ...

, 0+ , 0.019102(8) , , - , ¹²⁹XeUsed in a method of radiodating groundwater and to infer certain events in the Solar System's history , style="text-align:right" , 54 , style="text-align:right" , 75 , 128.9047794(8) , colspan=3 align=center, Stable , 1/2+ , 0.264006(82) , , - , style="text-indent:1em" , ^129mXe , colspan="3" style="text-indent:2em" , 236.14(3) keV , 8.88(2) d , IT , ¹²⁹Xe , 11/2− , , , - , ¹³⁰Xe , style="text-align:right" , 54 , style="text-align:right" , 76 , 129.9035080(8) , colspan=3 align=center, Stable , 0+ , 0.040710(13) , , - , ¹³¹Xe

Fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...

, style="text-align:right" , 54 , style="text-align:right" , 77 , 130.9050824(10) , colspan=3 align=center, Stable , 3/2+ , 0.212324(30) , , - , style="text-indent:1em" , ^131mXe , colspan="3" style="text-indent:2em" , 163.930(8) keV , 11.934(21) d , IT , ¹³¹Xe , 11/2− , , , - , ¹³²Xe , style="text-align:right" , 54 , style="text-align:right" , 78 , 131.9041535(10) , colspan=3 align=center, Stable , 0+ , 0.269086(33) , , - , style="text-indent:1em" , ^132mXe , colspan="3" style="text-indent:2em" , 2752.27(17) keV , 8.39(11) ms , IT , ¹³²Xe , (10+) , , , - , ¹³³XeHas medical uses , style="text-align:right" , 54 , style="text-align:right" , 79 , 132.9059107(26) , 5.2475(5) d , β⁻ , ¹³³Cs , 3/2+ , , , - , style="text-indent:1em" , ^133mXe , colspan="3" style="text-indent:2em" , 233.221(18) keV , 2.19(1) d , IT , ¹³³Xe , 11/2− , , , - , ¹³⁴Xe , style="text-align:right" , 54 , style="text-align:right" , 80 , 133.9053945(9) , colspan=3 align=center, Observationally StableSuspected of undergoing β⁻β⁻ decay to ¹³⁴Ba with a half-life over 11×10¹⁵ years , 0+ , 0.104357(21) , , - , style="text-indent:1em" , ^134m1Xe , colspan="3" style="text-indent:2em" , 1965.5(5) keV , 290(17) ms , IT , ¹³⁴Xe , 7− , , , - , style="text-indent:1em" , ^134m2Xe , colspan="3" style="text-indent:2em" , 3025.2(15) keV , 5(1) μs , , , (10+) , , , - , ¹³⁵XeMost powerful known neutron absorber, produced in nuclear power plants as a

decay product In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( ...

of ¹³⁵I, itself a decay product of ¹³⁵Te, a

. Normally absorbs neutrons in the high neutron flux environments to become ''¹³⁶Xe''; see iodine pit for more information , style="text-align:right" , 54 , style="text-align:right" , 81 , 134.907227(5) , 9.14(2) h , β⁻ , ¹³⁵Cs , 3/2+ , , , - , rowspan=2 style="text-indent:1em" , ^135mXe , rowspan=2 colspan="3" style="text-indent:2em" , 526.551(13) keV , rowspan=2, 15.29(5) min , IT (99.99%) , ¹³⁵Xe , rowspan=2, 11/2− , rowspan=2, , rowspan=2, , - , β⁻ (.004%) , ¹³⁵Cs , - , ¹³⁶Xe Primordial

, style="text-align:right" , 54 , style="text-align:right" , 82 , 135.907219(8) , 2.165(0.016 (stat), 0.059 (sys)) y , β⁻β⁻ , ¹³⁶Ba , 0+ , 0.088573(44) , , - , style="text-indent:1em" , ^136mXe , colspan="3" style="text-indent:2em" , 1891.703(14) keV , 2.95(9) μs , , , 6+ , , , - , ¹³⁷Xe , style="text-align:right" , 54 , style="text-align:right" , 83 , 136.911562(8) , 3.818(13) min , β⁻ , ¹³⁷Cs , 7/2− , , , - , ¹³⁸Xe , style="text-align:right" , 54 , style="text-align:right" , 84 , 137.91395(5) , 14.08(8) min , β⁻ , ¹³⁸Cs , 0+ , , , - , ¹³⁹Xe , style="text-align:right" , 54 , style="text-align:right" , 85 , 138.918793(22) , 39.68(14) s , β⁻ , ¹³⁹Cs , 3/2− , , , - , ¹⁴⁰Xe , style="text-align:right" , 54 , style="text-align:right" , 86 , 139.92164(7) , 13.60(10) s , β⁻ , ¹⁴⁰Cs , 0+ , , , - , rowspan=2, ¹⁴¹Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 87 , rowspan=2, 140.92665(10) , rowspan=2, 1.73(1) s , β⁻ (99.45%) , ¹⁴¹Cs , rowspan=2, 5/2(−#) , rowspan=2, , rowspan=2, , - , β⁻, n (.043%) , ¹⁴⁰Cs , - , rowspan=2, ¹⁴²Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 88 , rowspan=2, 141.92971(11) , rowspan=2, 1.22(2) s , β⁻ (99.59%) , ¹⁴²Cs , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β⁻, n (.41%) , ¹⁴¹Cs , - , ¹⁴³Xe , style="text-align:right" , 54 , style="text-align:right" , 89 , 142.93511(21)# , 0.511(6) s , β⁻ , ¹⁴³Cs , 5/2− , , , - , rowspan=2, ¹⁴⁴Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 90 , rowspan=2, 143.93851(32)# , rowspan=2, 0.388(7) s , β⁻ , ¹⁴⁴Cs , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β⁻, n , ¹⁴³Cs , - , ¹⁴⁵Xe , style="text-align:right" , 54 , style="text-align:right" , 91 , 144.94407(32)# , 188(4) ms , β⁻ , ¹⁴⁵Cs , (3/2−)# , , , - , ¹⁴⁶Xe , style="text-align:right" , 54 , style="text-align:right" , 92 , 145.94775(43)# , 146(6) ms , β⁻ , ¹⁴⁶Cs , 0+ , , , - , rowspan=2, ¹⁴⁷Xe , rowspan=2 style="text-align:right" , 54 , rowspan=2 style="text-align:right" , 93 , rowspan=2, 146.95356(43)# , rowspan=2, 130(80) ms
.10(+10−5) s, β⁻ , ¹⁴⁷Cs , rowspan=2, 3/2−# , rowspan=2, , rowspan=2, , - , β⁻, n , ¹⁴⁶Cs * The isotopic composition refers to that in air.

Xenon-124

Xenon-124 is an isotope of xenon that undergoes double electron capture to

tellurium Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...

-124 with a very long half life of years, more than 12 orders of magnitude longer than the age of the universe (). Such decays have been observed in the

XENON1T Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

detector in 2019, and are the rarest processes ever directly observed. (Even slower decays of other nuclei have been measured, but by detecting decay products that have accumulated over billions of years rather than observing them directly.)

Xenon-133

Xenon-133 (sold as a drug under the brand name ''Xeneisol'',

ATC code The Anatomical Therapeutic Chemical (ATC) Classification System is a drug classification system that classifies the active ingredients of drugs according to the organ or system on which they act and their therapeutic, pharmacological and chemical ...

) is an isotope of xenon. It is a

that is

inhaled Inhalation (or Inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

to assess pulmonary function, and to image the

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

s. It is also used to image blood flow, particularly in the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

. ¹³³Xe is also an important

. It is discharged to the atmosphere in small quantities by some nuclear power plants.

Xenon-135

Xenon-135 is a radioactive isotope of

, produced as a

of uranium. It has a

of about 9.2 hours and is the most powerful known

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

-absorbing nuclear poison (having a neutron absorption cross-section of 2 million

Chart of the Nuclides 13th Edition). The overall yield of xenon-135 from fission is 6.3%, though most of this results from the radioactive decay of fission-produced tellurium-135 and iodine-135. Xe-135 exerts a significant effect on

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nu ...

operation (

xenon pit The iodine pit, also called the iodine hole or xenon pit, is a temporary disabling of a nuclear reactor due to buildup of short- lived nuclear poisons in the reactor core. The main isotope responsible is 135Xe, mainly produced by natural decay of ...

). It is discharged to the atmosphere in small quantities by some nuclear power plants.

Xenon-136

Xenon-136 is an isotope of xenon that undergoes double beta decay to

barium Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

-136 with a very long half life of years, more than 10 orders of magnitude longer than the age of the universe (). It is being used in the

Enriched Xenon Observatory The Enriched Xenon Observatory (EXO) is a particle physics experiment searching for neutrinoless double beta decay of xenon-136 at WIPP near Carlsbad, New Mexico, U.S. Neutrinoless double beta decay (0νββ) detection would prove the Majorana ...

experiment to search for neutrinoless double beta decay.

References

* Isotope masses fro
Ame2003 Atomic Mass Evaluation
by Georges Audi, Aaldert Hendrik Wapstra, Catherine Thibault, Jean Blachot and Olivier Bersillon in ''Nuclear Physics'' A729 (2003). * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Xenon