Английская Википедия:Isotopes of oxygen

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

Radioactive isotopes ranging from Шаблон:SimpleNuclide to Шаблон:SimpleNuclide have also been characterized, all short-lived. The longest-lived radioisotope is Шаблон:SimpleNuclide with a half-life of Шаблон:Val, while the shortest-lived isotope is the unbound Шаблон:SimpleNuclide with a half-life of Шаблон:Val, though half-lives have not been measured for the unbound heavy isotopes Шаблон:SimpleNuclide and Шаблон:SimpleNuclide.

List of isotopes

Шаблон:Isotopes table |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 3 | Шаблон:Val | Шаблон:Val
[[[:Шаблон:Val]]] | 2p | Шаблон:SimpleNuclide | (3/2−) | | |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 4 | Шаблон:Val | Шаблон:Val | 2p | Шаблон:SimpleNuclide | 0+ | | |- | rowspan=3|Шаблон:SimpleNuclide | rowspan=3 style="text-align:right" | 8 | rowspan=3 style="text-align:right" | 5 | rowspan=3|Шаблон:Val | rowspan=3|Шаблон:Val | β⁺ (Шаблон:Val) | Шаблон:SimpleNuclide | rowspan=3|(3/2−) | rowspan=3| | rowspan=3| |- | β⁺p (Шаблон:Val) | Шаблон:SimpleNuclide |- | β⁺p,α (<Шаблон:Val) | 2Шаблон:SimpleNuclide |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 6 | Шаблон:Val | Шаблон:Val | β⁺ | Шаблон:SimpleNuclide | 0+ | | |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 7 | Шаблон:Val | Шаблон:Val | β⁺ | Шаблон:SimpleNuclide | 1/2− | colspan="2" style="text-align:center;"|Trace |- | [[Oxygen-16|Шаблон:SimpleNuclide]] | style="text-align:right" | 8 | style="text-align:right" | 8 | Шаблон:Val | colspan="3" style="text-align:center;"|Stable | 0+ | colspan="2" style="text-align:center;"|[[[:Шаблон:Val]], Шаблон:Val] |- | [[Oxygen-17|Шаблон:SimpleNuclide]] | style="text-align:right" | 8 | style="text-align:right" | 9 | Шаблон:Val | colspan="3" style="text-align:center;"|Stable | 5/2+ | colspan="2" style="text-align:center;"|[[[:Шаблон:Val]], Шаблон:Val] |- | [[Oxygen-18|Шаблон:SimpleNuclide]] | style="text-align:right" | 8 | style="text-align:right" | 10 | Шаблон:Val | colspan="3" style="text-align:center;"|Stable | 0+ | colspan="2" style="text-align:center;"|[[[:Шаблон:Val]], Шаблон:Val] |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 11 | Шаблон:Val | Шаблон:Val | β⁻ | Шаблон:SimpleNuclide | 5/2+ | | |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 12 | Шаблон:Val | Шаблон:Val | β⁻ | Шаблон:SimpleNuclide | 0+ | | |- | rowspan=2|Шаблон:SimpleNuclide | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 13 | rowspan=2|Шаблон:Val | rowspan=2|Шаблон:Val | β⁻ | Шаблон:SimpleNuclide | rowspan=2|(5/2+) | rowspan=2| | rowspan=2| |- | β⁻n ? | Шаблон:SimpleNuclide ? |- | rowspan=2|Шаблон:SimpleNuclide | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 14 | rowspan=2|Шаблон:Val | rowspan=2|Шаблон:Val | β⁻ (> Шаблон:Val) | Шаблон:SimpleNuclide | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁻n (< Шаблон:Val) | Шаблон:SimpleNuclide |- | rowspan=2|Шаблон:SimpleNuclide | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 15 | rowspan=2|Шаблон:Val | rowspan=2|Шаблон:Val | β⁻ (Шаблон:Val) | Шаблон:SimpleNuclide | rowspan=2|1/2+ | rowspan=2| | rowspan=2| |- | β⁻n (Шаблон:Val) | Шаблон:SimpleNuclide |- | rowspan=2|Шаблон:SimpleNuclide | rowspan=2 style="text-align:right" | 8 | rowspan=2 style="text-align:right" | 16 | rowspan=2|Шаблон:Val | rowspan=2|Шаблон:Val | β⁻ (Шаблон:Val) | Шаблон:SimpleNuclide | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁻n (Шаблон:Val) | Шаблон:SimpleNuclide |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 17 | Шаблон:Val | Шаблон:Val | n | Шаблон:SimpleNuclide | 3/2+Шаблон:Sup | | |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 18 | Шаблон:Val | Шаблон:Val | 2n | Шаблон:SimpleNuclide | 0+ | | |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 19 | | ≥ Шаблон:Val | n | Шаблон:SimpleNuclide | (3/2+, 7/2−) | | |- | Шаблон:SimpleNuclide | style="text-align:right" | 8 | style="text-align:right" | 20 | | ≥ Шаблон:Val | 2n | Шаблон:SimpleNuclide | 0+ | | Шаблон:Isotopes table/footer

Stable isotopes

Файл:Evolved star fusion shells.svg

Late in a massive star's life, Шаблон:SimpleNuclide concentrates in the N-shell, Шаблон:SimpleNuclide in the H-shell and Шаблон:SimpleNuclide in the He-shell.

Natural oxygen is made of three stable isotopes, [[Oxygen-16|Шаблон:SimpleNuclide]], [[Oxygen-17|Шаблон:SimpleNuclide]], and [[Oxygen-18|Шаблон:SimpleNuclide]], with Шаблон:SimpleNuclide being the most abundant (99.762% natural abundance). Depending on the terrestrial source, the standard atomic weight varies within the range of [[[:Шаблон:Val]], Шаблон:Val] (the conventional value is 15.999).

Шаблон: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. Most Шаблон:SimpleNuclide is synthesized at the end of the helium fusion process in stars; the triple-alpha process creates [[Carbon-12|Шаблон:SimpleNuclide]], which captures an additional [[Helium-4|Шаблон:SimpleNuclide]] nucleus to produce Шаблон:SimpleNuclide. The neon burning process creates additional Шаблон:SimpleNuclide.

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

An atomic mass of 16 was assigned to oxygen prior to the definition of the unified atomic mass unit based on Шаблон:SimpleNuclide.Шаблон:Sfn Since physicists referred to Шаблон: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 Шаблон:Val Шаблон:SimpleNuclide, Шаблон:Val Шаблон:SimpleNuclide and Шаблон:Val Шаблон:SimpleNuclide.Шаблон:Sfn Water molecules with a lighter isotope are slightly more likely to evaporate and less likely to fall as precipitation, so Earth's freshwater and polar ice have slightly less (Шаблон:Val) Шаблон:SimpleNuclide than air (Шаблон:Val) or seawater (Шаблон: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. Researchers need to avoid improper or prolonged storage of the samples for accurate measurements.

Due to natural oxygen being mostly Шаблон:Chem, 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 Шаблон:Chem, rather than in the also consumed Шаблон:CO2, by isotope tracing experiments. The oxygen contained in Шаблон:CO2 in turn is used to make up the sugars formed by photosynthesis.

In heavy water reactors the neutron moderator should preferably be low in Шаблон:Chem and Шаблон:Chem due to their higher neutron absorption cross section compared to Шаблон:Chem. 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 Шаблон:Chem and Шаблон:Chem can be measurably higher. Furthermore, the Шаблон:Chem(n,α)Шаблон:Chem 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.

Radioisotopes

Thirteen radioisotopes have been characterized; the most stable are Шаблон:SimpleNuclide with half-life Шаблон:Val and Шаблон:SimpleNuclide with half-life Шаблон:Val. All remaining radioisotopes have half-lives less than Шаблон:Val and most have half-lives less than 0.1 s. Four heaviest known isotopes (up to Шаблон:SimpleNuclide) decay by neutron emission to Шаблон:SimpleNuclide, whose half-life is Шаблон:Val. This isotope, along with ²⁸Ne, have been used in the model of reactions in crust of neutron stars. 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 Шаблон:Val. Its atomic mass is Шаблон:Val. It decays to nitrogen-13 by electron capture, with a decay energy of Шаблон: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.

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. It has an atomic mass of Шаблон:Val, and a half-life of Шаблон:Val. It is produced through deuteron bombardment of nitrogen-14 using a cyclotron.

Шаблон:SimpleNuclide + Шаблон:SimpleNuclide → Шаблон: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:

Шаблон:SimpleNuclide + γ → Шаблон:SimpleNuclide + n

Шаблон:SimpleNuclide + γ → Шаблон:SimpleNuclide + n

Шаблон:SimpleNuclide decays to Шаблон: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 Шаблон:SimpleNuclide and Шаблон:SimpleNuclide floats by, carried by the wind.

Oxygen-20

Oxygen-20 has a half-life of Шаблон: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 Шаблон:Val.

See also

• Dole effect

References

• Шаблон:Cite book
• Шаблон:Cite book
• Шаблон:Cite book