CarbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
(
C) has 16 known
isotopeIsotopes 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, from
8C to
23C, 2 of which (
12CCarbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....
and
13CCarbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
) are stable. The longest-lived radioisotope is
14CCarbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
with a
half-lifeHalf-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 5,700 years. This is also the only carbon radioisotope found in nature, where trace quantities are formed cosmogenically by the reaction
14N +
1n ->
14C +
1H. The most stable artificial radioisotope is
11C, with a half-life of 20.334 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is
8C, with a half-life of 2.0 x 10
−21 s.
Standard atomic mass: 12.0107(8) u
Carbon-11
Carbon-11 or
11C is a radioactive isotope of
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
. It decays 100% by
positron emissionPositron emission or beta plus decay is a type of beta decay in which a proton is converted, via the weak force, to a neutron, releasing a positron and a neutrino....
to boron-11. It has a
half-lifeHalf-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 20.38 minutes.
- → + + +
Carbon-11 is commonly used as a radioisotope to radioactive labeling of molecules in
positron emission tomographyPositron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
. Among the many molecules used in this context is the
radioligandA radioligand is a radioactive biochemical substance that is used for diagnosis or for research-oriented study of the receptor systems of the body....
[
CarbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
(C) has 16 known isotopeIsotopes 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, from
8C to
23C, 2 of which (
12CCarbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....
and
13CCarbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
) are stable. The longest-lived radioisotope is
14CCarbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
with a
half-lifeHalf-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 5,700 years. This is also the only carbon radioisotope found in nature, where trace quantities are formed cosmogenically by the reaction
14N +
1n ->
14C +
1H. The most stable artificial radioisotope is
11C, with a half-life of 20.334 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is
8C, with a half-life of 2.0 x 10
−21 s.
Standard atomic mass: 12.0107(8) u
Carbon-11
Carbon-11 or
11C is a radioactive isotope of
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
. It decays 100% by
positron emissionPositron emission or beta plus decay is a type of beta decay in which a proton is converted, via the weak force, to a neutron, releasing a positron and a neutrino....
to boron-11. It has a
half-lifeHalf-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 20.38 minutes.
- {{SimpleNuclide|Carbon|11}} → {{SimpleNuclide|link|Boron|11}} + {{SubatomicParticle|link=yes|positron}} + {{SubatomicParticle|link=yes|Electron neutrino}} + {{Val|0.96|ul=MeV}}
Carbon-11 is commonly used as a radioisotope to radioactive labeling of molecules in
positron emission tomographyPositron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
. Among the many molecules used in this context is the
radioligandA radioligand is a radioactive biochemical substance that is used for diagnosis or for research-oriented study of the receptor systems of the body....
[
CarbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
(C) has 16 known isotopeIsotopes 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, from
8C to
23C, 2 of which (
12CCarbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....
and
13CCarbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
) are stable. The longest-lived radioisotope is
14CCarbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
with a
half-lifeHalf-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 5,700 years. This is also the only carbon radioisotope found in nature, where trace quantities are formed cosmogenically by the reaction
14N +
1n ->
14C +
1H. The most stable artificial radioisotope is
11C, with a half-life of 20.334 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is
8C, with a half-life of 2.0 x 10
−21 s.
Standard atomic mass: 12.0107(8) u
Carbon-11
Carbon-11 or
11C is a radioactive isotope of
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
. It decays 100% by
positron emissionPositron emission or beta plus decay is a type of beta decay in which a proton is converted, via the weak force, to a neutron, releasing a positron and a neutrino....
to boron-11. It has a
half-lifeHalf-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 20.38 minutes.
- {{SimpleNuclide|Carbon|11}} → {{SimpleNuclide|link|Boron|11}} + {{SubatomicParticle|link=yes|positron}} + {{SubatomicParticle|link=yes|Electron neutrino}} + {{Val|0.96|ul=MeV}}
Carbon-11 is commonly used as a radioisotope to radioactive labeling of molecules in
positron emission tomographyPositron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
. Among the many molecules used in this context is the
radioligandA radioligand is a radioactive biochemical substance that is used for diagnosis or for research-oriented study of the receptor systems of the body....
[{{SimpleNuclideDASB is a compound that binds to the serotonin transporter.Labeled with carbon-11 — a radioactive isotope — it has been used as a radioligand in neuroimaging with positron emission tomography since around year 2000....
.
Natural isotopes
{{main|Carbon-12|Carbon-13|Carbon-14}}
There are 3 naturally occurring isotopes of carbon: 12, 13, and 14.
12C and
13C are stable, occurring in a natural proportion of approximately 99:1.
14C is produced by thermal neutrons from cosmic radiation in the upper atmosphere, and is transported down to earth to be absorbed by living biological material. Isotopically the
14C constitutes a negligible part, but since it is radioactive with a half-life of 5700 years, it is radiometrically detectable. Since dead tissue doesn't absorb
14C, the amount of
14C is used for radiometric dating of biological material, among others within the field of archeology.
Table
nuclide
symbol |
Z(pThe 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(nThe 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) |
daughter
isotope(s)[Bold for stable isotopes] |
nuclear
spin |
representative
isotopic
composition
(mole fraction) |
range of natural
variation
(mole fraction) |
| 8C |
6 |
2 |
8.037675(25) |
2.0(4) x 10−21 s
[230(50) keV] |
2p 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...
|
{{SimpleNuclide|Beryllium|6}}[Subsequently decays by double proton emission to 4He for a net reaction of 8C -> 4He + 41H] |
0+ |
|
|
| 9C |
6 |
3 |
9.0310367(23) |
126.5(9) ms |
β+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...
(60%) |
{{SimpleNuclide|Boron|9}}[Immediately decays by proton emission to 8Be, which immediately decays to two 4He atoms for a net reaction of 9C -> 24He + 1H + e+] |
(3/2-) |
|
|
| β+, p (23%) |
{{SimpleNuclide|Beryllium|8}}[Immediately decays into two 4He atoms for a net reaction of 9C -> 24He + 1H + e+] |
β+, αAlpha 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...
(17%) |
{{SimpleNuclide|Lithium|5}}[Immediately decays by proton emission to 4He for a net reaction of 9C -> 24He + 1H + e+] |
| 10C |
6 |
4 |
10.0168532(4) |
19.290(12) s |
β+ |
{{SimpleNuclide|Boron|10}} |
0+ |
|
|
11C[Used for labeling molecules in PET scans]Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
|
6 |
5 |
11.0114336(10) |
20.334(24) min |
β+ |
{{SimpleNuclide|Boron|11}} |
3/2- |
|
|
| 12C Carbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....
|
6 |
6 |
12 exactly[The unified atomic mass unit is defined as 1/12 the mass of an unbound atom of Carbon-12 at ground state] |
Stable |
0+ |
0.9893(8) |
0.98853-0.99037 |
| 13C Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
[Ratio of 12C to 13C used to measure biological productivity in ancient times and differing types of photosynthesis]Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
|
6 |
7 |
13.0033548378(10) |
Stable |
1/2- |
0.0107(8) |
0.00963-0.01147 |
14CCarbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
[Has an important use in radiodating (see carbon dating)] |
6 |
8 |
14.003241989(4) |
5.70(3) x 103 years |
β− |
{{SimpleNuclide|Nitrogen|14}} |
0+ |
Trace[Primarily cosmogenic, produced by 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...
s striking atoms of 14N (14N + 1n -> 14C + 1H) |
<10−12 |
| 15C |
6 |
9 |
15.0105993(9) |
2.449(5) s |
β− |
{{SimpleNuclide|Nitrogen|15}} |
1/2+ |
|
|
| 16C |
6 |
10 |
16.014701(4) |
0.747(8) s |
β−, nNeutron 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...
(97.9%) |
{{SimpleNuclide|Nitrogen|15}} |
0+ |
|
|
| β− (2.1%) |
{{SimpleNuclide|Nitrogen|16}} |
| 17C |
6 |
11 |
17.022586(19) |
193(5) ms |
β− (71.59%) |
{{SimpleNuclide|Nitrogen|17}} |
(3/2+) |
|
|
| β−, n (28.41%) |
{{SimpleNuclide|Nitrogen|16}} |
| 18C |
6 |
12 |
18.02676(3) |
92(2) ms |
β− (68.5%) |
{{SimpleNuclide|Nitrogen|18}} |
0+ |
|
|
| β−, n (31.5%) |
{{SimpleNuclide|Nitrogen|17}} |
19C[Has 1 halo neutron] |
6 |
13 |
19.03481(11) |
46.2(23) ms |
β−, n (47.0%) |
{{SimpleNuclide|Nitrogen|18}} |
(1/2+) |
|
|
| β− (46.0%) |
{{SimpleNuclide|Nitrogen|19}} |
| β−, 2n (7%) |
{{SimpleNuclide|Nitrogen|17}} |
| 20C |
6 |
14 |
20.04032(26) |
16(3) ms
[14(+6-5) ms] |
β−, n (72.0%) |
{{SimpleNuclide|Nitrogen|19}} |
0+ |
|
|
| β− (28.0%) |
{{SimpleNuclide|Nitrogen|20}} |
| 21C |
6 |
15 |
21.04934(54)# |
<30 ns |
n |
{{SimpleNuclide|Carbon|20}} |
(1/2+)# |
|
|
22C[Has 2 halo neutrons] |
6 |
16 |
22.05720(97)# |
6.2(13) ms
[6.1(+14-12) ms] |
β− |
{{SimpleNuclide|Nitrogen|22}} |
0+ |
|
|
Paleoclimate
{{Confusing|date=April 2009}}
12C and
13C are measured as the isotope ratio δ
13C in benthic foraminifera and used as a proxy for nutrient cycling and the temperature dependant air-sea exchange of CO
2 (ventilation) (Lynch-Stieglitz et al., 1995). Plants find it easier to use the lighter isotopes (
12C) when they convert sunlight and carbon dioxide into food. So, for example, large blooms of plankton (free-floating organisms) absorb large amounts of
12C from the oceans. The
12C was originally mostly incorporated into the seawater from the atmosphere. If the oceans the plankton live in are stratified (meaning that there are layers of warm water near the top, and colder water deeper down) the surface water does not mix with deeper waters very much, so that when the plankton dies it sinks and takes away
12C from the surface, leaving the surface layers relatively rich in
13C. Where cold waters well up from the depths (such as in the North Atlantic) it carries
12C back up with it. So, when the ocean was less stratified than today, there was much more
12C in the skeletons of surface-dwelling species. Other indicators of past climate include the presence of tropical species, coral growths rings, etc. (Flannery, 2005)
Tracing food sources and diets
The quantities of the different isotopes can be measured by
mass spectrometryMass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...
and compared to a standard; the result (e.g. the delta of the
13C = δ
13C) is expressed as parts per thousand (‰).
Stable carbon isotopes in
carbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
are utilized differentially by plants during
photosynthesisPhotosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. Grasses in temperate environments (
barleyBarley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
,
riceRice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
,
wheatWheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
,
ryeRye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...
and
oatsOATS - Open Source Assistive Technology Software - is a source code repository or "forge" for assistive technology software. It was launched in 2006 with the goal to provide a one-stop “shop” for end users, clinicians and open-source developers to promote and develop open source assistive...
, plus
sunflowerSunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...
,
potatoThe potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
,
tomatoThe word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...
es,
peanutThe peanut, or groundnut , is a species in the legume or "bean" family , so it is not a nut. The peanut was probably first cultivated in the valleys of Peru. It is an annual herbaceous plant growing tall...
s,
cottonCotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
,
sugar beetSugar beet, a cultivated plant of Beta vulgaris, is a plant whose tuber contains a high concentration of sucrose. It is grown commercially for sugar production. Sugar beets and other B...
, and most trees and their nuts/fruits,
roseA rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...
s and Kentucky bluegrass) follow a
C3 photosynthetic pathway carbon fixation is a metabolic pathway for carbon fixation in photosynthesis. This process converts carbon dioxide and ribulose bisphosphate into 3-phosphoglycerate through the following reaction:...
that will yield δ
13C values averaging about −26.5‰. Grasses in hot arid environments (
maizeMaize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
in particular, but also
milletThe millets are a group of small-seeded species of cereal crops or grains, widely grown around the world for food and fodder. They do not form a taxonomic group, but rather a functional or agronomic one. Their essential similarities are that they are small-seeded grasses grown in difficult...
,
sorghumSorghum is a genus of numerous species of grasses, one of which is raised for grain and many of which are used as fodder plants either cultivated or as part of pasture. The plants are cultivated in warmer climates worldwide. Species are native to tropical and subtropical regions of all continents...
, sugar cane and crabgrass) follow a
C4 photosynthetic pathwayC4 carbon fixation is one of three biochemical mechanisms, along with and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3-carbon molecule products in plants. fixation is an...
that produces δ
13C values averaging about −12.5‰.
It follows that eating these different plants will affect the δ
13C values in the consumer’s body tissues. If an animal (or human) eats only C3 plants, their δ
13C values will be −12.5‰ in their bone
collagenCollagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
and −14.5‰ in their
apatiteApatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
.
In contrast, C4 feeders will have bone collagen with a value of −7.5‰ and apatite value of −0.5‰.
In actual case studies, millet and maize eaters can easily be distinguished from rice and wheat eaters. Studying how these dietary preferences are distributed geographically through time can illuminate migration paths of people and dispersal paths of different agricultural crops. However, human groups have often mixed C3 and C4 plants (northern Chinese historically subsisted on wheat and millet), or mixed plant and animal groups together (for example, southeastern Chinese subsisting on rice and fish).
See also
- radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
- Cosmogenic isotopes
- Environmental isotopes
The environmental isotopes are a subset of the isotopes, both stable and radioactive, which are the object of Isotope geochemistry.The most used environmental isotopes are:* deuterium* tritium* carbon-13* carbon-14* nitrogen-15* oxygen-18...
- Isotopic signature
An isotopic signature is a ratio of stable or unstable isotopes of particular elements found in an investigated material...