Isotopes of oxygen

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Template:Short description Template:Infobox oxygen isotopes

There are three known stable isotopes of oxygen (8O): [[Oxygen-16|Template:SimpleNuclide]], [[Oxygen-17|Template:SimpleNuclide]], and [[Oxygen-18|Template:SimpleNuclide]].

Radioactive isotopes ranging from Template:SimpleNuclide to Template:SimpleNuclide have also been characterized, all short-lived. The longest-lived radioisotope is Template:SimpleNuclide with a half-life of Script error: No such module "val"., while the shortest-lived isotope is the unbound Template:SimpleNuclide with a half-life of Script error: No such module "val"., though half-lives have not been measured for the unbound heavy isotopes Template:SimpleNuclide and Template:SimpleNuclide.[1]

List of isotopes

Template:Isotopes table |-id=Oxygen-11 | Template:SimpleNuclide[2] | style="text-align:right" | 8 | style="text-align:right" | 3 | Script error: No such module "val". | Script error: No such module "val".
[Script error: No such module "val".] | 2p | Template:SimpleNuclide | (3/2−) | | |-id=Oxygen-12 | Template:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 4 | Script error: No such module "val". | Script error: No such module "val". | 2p | Template:SimpleNuclide | 0+ | | |- | rowspan=3|Template:SimpleNuclide | rowspan=3 style="text-align:right" | 8 | rowspan=3 style="text-align:right" | 5 | rowspan=3|Script error: No such module "val". | rowspan=3|Script error: No such module "val". | β+ (Script error: No such module "val".) | Template:SimpleNuclide | rowspan=3|(3/2−) | rowspan=3| | rowspan=3| |- | β+p (Script error: No such module "val".) | Template:SimpleNuclide |- | β+p,α (<Script error: No such module "val".) | 2Template:SimpleNuclide[3] |- | Template:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 6 | Script error: No such module "val". | Script error: No such module "val". | β+ | Template:SimpleNuclide | 0+ | | |- | Template:SimpleNuclide[n 1] | style="text-align:right" | 8 | style="text-align:right" | 7 | Script error: No such module "val". | Script error: No such module "val". | β+ | Template:SimpleNuclide | 1/2− | colspan="2" style="text-align:center;"|Trace[4] |- | [[Oxygen-16|Template:SimpleNuclide]][n 2] | style="text-align:right" | 8 | style="text-align:right" | 8 | Script error: No such module "val". | colspan="3" style="text-align:center;"|Stable | 0+ | colspan="2" style="text-align:center;"|[Script error: No such module "val"., Script error: No such module "val".][5] |- | [[Oxygen-17|Template:SimpleNuclide]][n 3] | style="text-align:right" | 8 | style="text-align:right" | 9 | Script error: No such module "val". | colspan="3" style="text-align:center;"|Stable | 5/2+ | colspan="2" style="text-align:center;"|[Script error: No such module "val"., Script error: No such module "val".][5] |- | [[Oxygen-18|Template:SimpleNuclide]][n 2][n 4] | style="text-align:right" | 8 | style="text-align:right" | 10 | Script error: No such module "val". | colspan="3" style="text-align:center;"|Stable | 0+ | colspan="2" style="text-align:center;"|[Script error: No such module "val"., Script error: No such module "val".][5] |-id=Oxygen-19 | Template:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 11 | Script error: No such module "val". | Script error: No such module "val". | β− | Template:SimpleNuclide | 5/2+ | | |- | Template:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 12 | Script error: No such module "val". | Script error: No such module "val". | β− | Template:SimpleNuclide | 0+ | | |-id=Oxygen-21 | rowspan=2|Template:SimpleNuclide | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 13 | rowspan=2|Script error: No such module "val". | rowspan=2|Script error: No such module "val". | β− | Template:SimpleNuclide | rowspan=2|(5/2+) | rowspan=2| | rowspan=2| |- | β−n ?[n 5] | Template:SimpleNuclide ? |-id=Oxygen-22 | rowspan=2|Template:SimpleNuclide | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 14 | rowspan=2|Script error: No such module "val". | rowspan=2|Script error: No such module "val". | β− (> Script error: No such module "val".) | Template:SimpleNuclide | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β−n (< Script error: No such module "val".) | Template:SimpleNuclide |-id=Oxygen-23 | rowspan=2|Template:SimpleNuclide | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 15 | rowspan=2|Script error: No such module "val". | rowspan=2|Script error: No such module "val". | β− (Script error: No such module "val".) | Template:SimpleNuclide | rowspan=2|1/2+ | rowspan=2| | rowspan=2| |- | β−n (Script error: No such module "val".) | Template:SimpleNuclide |-id=Oxygen-24 | rowspan=2|Template:SimpleNuclide[n 6] | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 16 | rowspan=2|Script error: No such module "val". | rowspan=2|Script error: No such module "val". | β− (Script error: No such module "val".) | Template:SimpleNuclide | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β−n (Script error: No such module "val".) | Template:SimpleNuclide |-id=Oxygen-25 | Template:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 17 | Script error: No such module "val". | Script error: No such module "val". | n | Template:SimpleNuclide | 3/2+# | | |-id=Oxygen-26 | Template:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 18 | Script error: No such module "val". | Script error: No such module "val". | 2n | Template:SimpleNuclide | 0+ | | |-id=Oxygen-27 | Template:SimpleNuclide[1] | style="text-align:right" | 8 | style="text-align:right" | 19 | | ≥ Script error: No such module "val". | n | Template:SimpleNuclide | (3/2+, 7/2−) | | |-id=Oxygen-28 | Template:SimpleNuclide[1] | style="text-align:right" | 8 | style="text-align:right" | 20 | | ≥ Script error: No such module "val". | 2n | Template:SimpleNuclide | 0+ | | Template:Isotopes table/footer

Stable isotopes

File:Evolved star fusion shells.svg
Late in a massive star's life, Template:SimpleNuclide concentrates in the Ne-shell, Template:SimpleNuclide in the H-shell and Template:SimpleNuclide in the He-shell.

Natural oxygen is made of three stable isotopes, [[Oxygen-16|Template:SimpleNuclide]], [[Oxygen-17|Template:SimpleNuclide]], and [[Oxygen-18|Template:SimpleNuclide]], with Template:SimpleNuclide being the most abundant (99.762% natural abundance). Depending on the terrestrial source, the standard atomic weight varies within the range of [Script error: No such module "val"., Script error: No such module "val".] (the conventional value is 15.999).

Template:SimpleNuclide has high relative and absolute abundance because it is a principal product of stellar evolution and because it is a primary isotope, meaning it can be made by stars that were initially hydrogen only.[6] Most Template:SimpleNuclide is synthesized at the end of the helium fusion process in stars; the triple-alpha process creates [[Carbon-12|Template:SimpleNuclide]], which captures an additional [[Helium-4|Template:SimpleNuclide]] nucleus to produce Template:SimpleNuclide. The neon burning process creates additional Template:SimpleNuclide.[6]

Both Template:SimpleNuclide and Template:SimpleNuclide are secondary isotopes, meaning their synthesis requires seed nuclei. Template:SimpleNuclide is primarily made by burning hydrogen into helium in the CNO cycle, making it a common isotope in the hydrogen burning zones of stars.[6] Most Template:SimpleNuclide is produced when [[Nitrogen|Template:SimpleNuclide]] (made abundant from CNO burning) captures a Template:SimpleNuclide nucleus, becoming [[Fluorine-18|Template:SimpleNuclide]]. This quickly (half-life around 110 minutes) beta decays to Template:SimpleNuclide making that isotope common in the helium-rich zones of stars.[6] Temperatures on the order of 109 kelvins are needed to fuse oxygen into sulfur.Template:Sfn

An atomic mass of 16 was assigned to oxygen prior to the definition of the dalton based on Template:SimpleNuclide.Template:Sfn Since physicists referred to Template:SimpleNuclide only, while chemists meant the natural mix of isotopes, this led to slightly different mass scales.

Applications of various isotopes

Measurements of 18O/16O ratio are often used to interpret changes in paleoclimate. Oxygen in Earth's air is Script error: No such module "val". Template:SimpleNuclide, Script error: No such module "val". Template:SimpleNuclide and Script error: No such module "val". Template:SimpleNuclide.Template:Sfn Water molecules with a lighter isotope are slightly more likely to evaporate and less likely to fall as precipitation,[7] so Earth's freshwater and polar ice have slightly less (Script error: No such module "val".) Template:SimpleNuclide than air (Script error: No such module "val".) or seawater (Script error: No such module "val".). This disparity allows analysis of temperature patterns via historic ice cores.

Solid samples (organic and inorganic) for oxygen isotopic ratios are usually stored in silver cups and measured with pyrolysis and mass spectrometry.[8] Researchers need to avoid improper or prolonged storage of the samples for accurate measurements.[8]

Due to natural oxygen being mostly Template:Chem/link, samples enriched with the other stable isotopes can be used for isotope labeling. For example, it was proven that the oxygen released in photosynthesis originates in Template:Chem/link, rather than in the also consumed CO2, by isotope tracing experiments. The oxygen contained in CO2 in turn is used to make up the sugars formed by photosynthesis.

In heavy-water nuclear reactors the neutron moderator should preferably be low in Template:Chem/link and Template:Chem/link due to their higher neutron absorption cross section compared to Template:Chem/link. While this effect can also be observed in light-water reactors, ordinary hydrogen (protium) has a higher absorption cross section than any stable isotope of oxygen and its number density is twice as high in water as that of oxygen, so that the effect is negligible. As some methods of isotope separation enrich not only heavier isotopes of hydrogen but also heavier isotopes of oxygen when producing heavy water, the concentration of Template:Chem/link and Template:Chem/link can be measurably higher. Furthermore, the Template:Chem/link(n,α)Template:Chem/link reaction is a further undesirable result of an elevated concentration of heavier isotopes of oxygen. Therefore, facilities which remove tritium from heavy water used in nuclear reactors often also remove or at least reduce the amount of heavier isotopes of oxygen.

Oxygen isotopes are also used to trace ocean composition and temperature which seafood is from.[9]

Radioisotopes

Thirteen radioisotopes have been characterized; the most stable are Template:SimpleNuclide with half-life Script error: No such module "val". and Template:SimpleNuclide with half-life Script error: No such module "val".. All remaining radioisotopes have half-lives less than Script error: No such module "val". and most have half-lives less than 0.1 s. The four heaviest known isotopes (up to Template:SimpleNuclide) decay by neutron emission to Template:SimpleNuclide, whose half-life is Script error: No such module "val".. This isotope, along with 28Ne, have been used in the model of reactions in crust of neutron stars.[10] The most common decay mode for isotopes lighter than the stable isotopes is β+ decay to nitrogen, and the most common mode after is β− decay to fluorine.

Oxygen-13

Oxygen-13 is an unstable isotope, with 8 protons and 5 neutrons. It has spin 3/2−, and half-life Script error: No such module "val".. Its atomic mass is Script error: No such module "val".. It decays to nitrogen-13 by electron capture, with a decay energy of Script error: No such module "val".. Its parent nuclide is fluorine-14.

Oxygen-14

Oxygen-14 is the second most stable radioisotope. Oxygen-14 ion beams are of interest to researchers of proton-rich nuclei; for example, one early experiment at the Facility for Rare Isotope Beams in East Lansing, Michigan, used a 14O beam to study the beta decay transition of this isotope to 14N.[11][12]

Oxygen-15

Oxygen-15 is a radioisotope, often used in positron emission tomography (PET). It can be used in, among other things, water for PET myocardial perfusion imaging and for brain imaging.[13][14] It has an atomic mass of Script error: No such module "val"., and a half-life of Script error: No such module "val".. It is produced through deuteron bombardment of nitrogen-14 using a cyclotron.[15]

Template:SimpleNuclide + Template:SimpleNuclide → Template:SimpleNuclide + n

Oxygen-15 and nitrogen-13 are produced in air when gamma rays (for example from lightning) knock neutrons out of 16O and 14N:[16]

Template:SimpleNuclide + γ → Template:SimpleNuclide + n
Template:SimpleNuclide + γ → Template:SimpleNuclide + n

Template:SimpleNuclide decays to Template:SimpleNuclide, emitting a positron. The positron quickly annihilates with an electron, producing two gamma rays of about 511 keV. After a lightning bolt, this gamma radiation dies down with half-life of 2 minutes, but these low-energy gamma rays go on average only about 90 metres through the air. Together with rays produced from positrons from nitrogen-13 they may only be detected for a minute or so as the "cloud" of Template:SimpleNuclide and Template:SimpleNuclide floats by, carried by the wind.[4]

Oxygen-20

Oxygen-20 has a half-life of Script error: No such module "val". and decays by β− decay to 20F. It is one of the known cluster decay ejected particles, being emitted in the decay of 228Th with a branching ratio of about Script error: No such module "val"..[17]

See also

Daughter products other than oxygen

References

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