Deuterium

Deuterium

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Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

. It has a natural abundance
Natural abundance
In chemistry, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table...

 in Earth's oceans of about one atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

 in of hydrogen ( on an atom basis). Deuterium accounts for approximately 0.0156% (or on a mass basis: 0.0312%) of all naturally occurring hydrogen in Earth's oceans, while the most common isotope (hydrogen-1
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 or protium) accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another (see VSMOW).

The nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 of deuterium, called a deuteron, contains one proton
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....

 and one neutron
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...

, whereas the far more common hydrogen isotope, protium, has no neutron in the nucleus. The deuterium isotope's name is formed from the Greek deuteros meaning "second", to denote the two particles composing the nucleus. Deuterium was discovered and named in 1931 by Harold Urey
Harold Urey
Harold Clayton Urey was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934...

, earning him a Nobel Prize in 1934 after the discovery of the neutron in 1932 made the structure of deuterium obvious. Soon after deuterium's discovery, Urey and others produced samples of water in which deuterium has been highly concentrated with respect to protium, a substance popularly known as heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

.

Because deuterium is destroyed in the interiors of stars faster than it is produced, and because other natural processes are thought to produce only an insignificant amount of deuterium, it is presently thought that nearly all deuterium found in nature was produced in the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 13.7 billion years ago, and that the basic or primordial ratio of hydrogen-1 (protium) to deuterium (about 26 atoms of deuterium per million hydrogen) has its origin from that time. This is the ratio found in the gas giant planets, such as Jupiter. However, different astronomical bodies are found to have different ratios of deuterium to hydrogen-1, and this is thought to be as a result of natural isotope separation processes that occur from solar heating of ices in comets. Like the water-cycle in Earth's weather, such heating processes may enrich deuterium with respect to protium. In fact, the discovery of deuterium/protium ratios in a number of comets very simlar to the mean ratio in Earth's oceans, has led to theories that much of Earth's ocean water has a cometary origin.

Deuterium/protium ratios thus continue to be an active topic of research in both astronomy and climatology.

Chemical symbol



Deuterium is frequently represented by the chemical symbol
Chemical symbol
A chemical symbol is a 1- or 2-letter internationally agreed code for a chemical element, usually derived from the name of the element, often in Latin. Only the first letter is capitalised...

 D. Since it is an isotope of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 with mass number
Mass number
The mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...

 2, it is also represented by . IUPAC allows both D and , although is preferred. A distinct chemical symbol is used for convenience because of the isotope's common use in various scientific processes. Also, its large mass difference with protium  (deuterium has a mass of , compared to the mean
Mean
In statistics, mean has two related meanings:* the arithmetic mean .* the expected value of a random variable, which is also called the population mean....

 hydrogen atomic weight
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...

 of , and protium's mass of ) confers non-negligible chemical dissimilarities with protium-containing compounds, whereas the isotope weight ratios within other chemical elements are largely insignificant in this regard.

Natural abundance



Deuterium occurs in trace amounts naturally as deuterium gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

, written 2 or D2, but most natural occurrence in the universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 is bonded with a typical atom, a gas called hydrogen deuteride
Hydrogen deuteride
Hydrogen deuteride is a diatomic molecule composed of the two isotopes of hydrogen: the majority isotope 1H protium and 2H deuterium. Its molecular formula is HD.- Availability in nature :...

 (HD or ).

The natural deuterium abundance seems to be a very similar fraction of hydrogen, wherever hydrogen is found. Thus, the existence of deuterium at a low but constant fraction in all hydrogen, is one of the arguments in favor of the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 theory over the Steady State theory
Steady State theory
In cosmology, the Steady State theory is a model developed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others as an alternative to the Big Bang theory...

 of the universe. It is estimated that the abundances of deuterium have not evolved significantly since their production about .

Deuterium abundance on Jupiter has been directly measured at 26 atoms D per million hydrogens by the Galileo entry probe; ISO-SWS observations find 22 atoms of D per million H atoms in Jupiter. and this abundance is thought to represent close to the primordial solar system ratio. This is about 17% of the terrestrial deuterium-to-hydrogen ratio of 156 deuterium atoms per million hydrogen atoms.

Cometary bodies such as Comet Hale Bopp and Halley's Comet have been measured to contain relatively more deuterium (about 200 atoms D per million hydrogens), ratios which are enriched with respect to the presumed protosolar nebula ratio, probably due to heating, and which are similar to the ratios found in Earth seawater. The recent measurement of deuterium amounts of 161 atoms D per million hydrogen in Comet 103P/Hartley
103P/Hartley
Comet Hartley 2, designated as 103P/Hartley by the Minor Planet Center, is a small periodic comet with an orbital period of 6.46 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit, Siding Spring Observatory, Australia...

 (a former Kuiper belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...

 object), a ratio almost exactly that in Earth's oceans, emphasizes the theory that Earth's surface water may be largely comet-derived.

There is thought to be little deuterium in the interior of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and other stars, as at temperatures there nuclear fusion reactions that consume deuterium happen much faster than the proton-proton reaction that creates deuterium. However, it continues to persist in the outer solar atmosphere at roughly the same concentration as in Jupiter.

The existence of deuterium on Earth, elsewhere in the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 (as confirmed by planetary probes), and in the spectra of star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s, is an important datum in cosmology
Physical cosmology
Physical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...

. Gamma radiation from ordinary nuclear fusion dissociates deuterium into protons and neutrons, and there are no known natural processes other than the Big Bang nucleosynthesis
Big Bang nucleosynthesis
In physical cosmology, Big Bang nucleosynthesis refers to the production of nuclei other than those of H-1 during the early phases of the universe...

, which might have produced deuterium at anything close to the observed natural abundance of deuterium (deuterium is produced by the rare cluster decay
Cluster decay
Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy...

, and occasional absorption of naturally occurring neutrons by light hydrogen, but these are trivial sources).

Concentrating natural abundance deuterium


Deuterium is concentrated for industrial, scientific and military purposes as heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

 from ordinary water. The world's leading supplier of deuterium was Atomic Energy of Canada Limited
Atomic Energy of Canada Limited
Atomic Energy of Canada Limited or AECL is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory...

, in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, until 1997, when the last heavy water plant was shut down. Canada uses heavy water as a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

 for the operation of the CANDU reactor
CANDU reactor
The CANDU reactor is a Canadian-invented, pressurized heavy water reactor. The acronym refers to its deuterium-oxide moderator and its use of uranium fuel...

 design.

Physical properties


The physical properties of deuterium compounds can exhibit significant kinetic isotope effect
Kinetic isotope effect
The kinetic isotope effect is the ratio of reaction rates of two different isotopically labeled molecules in a chemical reaction. It is also called "isotope fractionation," although this term is somewhat broader in meaning...

s and other physical and chemical property differences from the hydrogen analogs; for example, D2O is more viscous
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 than H2O
H2O
H2O is the chemical formula for water and is also used as an abbreviation for the word "water". H2O or H2O It may also refer to:* H2O , a punk band**H2O , their self-titled debut album...

.
Chemically, deuterium behaves similarly to ordinary hydrogen, but there are differences in bond energy and length for compounds of heavy hydrogen isotopes which are larger than the isotopic differences in any other element. Bonds involving deuterium and tritium
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...

 are somewhat stronger than the corresponding bonds in hydrogen, and these differences are enough to make significant changes in biological reactions.

Deuterium can replace the normal hydrogen in water molecules to form heavy water (D2O), which is about 10.6% denser than normal water (enough that ice made from it sinks in ordinary water). Heavy water is slightly toxic in eukaryotic animals, with 25% substitution of the body water causing cell division problems and sterility, and 50% substitution causing death by cytotoxic syndrome (bone marrow failure and gastrointestinal lining failure). Prokaryotic organisms, however, can survive and grow in pure heavy water (though they grow more slowly). Consumption of heavy water does not pose a health threat to humans, it is estimated that a person might drink 4.8 liters of heavy water without serious consequences. Small doses of heavy water (a few grams in humans, containing an amount of deuterium comparable to that normally present in the body) are routinely used as harmless metabolic tracers in humans and animals.

Quantum properties


The deuteron has spin +1 ("triplet") and is thus a boson
Boson
In particle physics, bosons are subatomic particles that obey Bose–Einstein statistics. Several bosons can occupy the same quantum state. The word boson derives from the name of Satyendra Nath Bose....

. The NMR
Nuclear magnetic resonance
Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...

 frequency of deuterium is significantly different from common light hydrogen. Infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...

 also easily differentiates many deuterated compounds, due to the large difference in IR absorption frequency seen in the vibration of a chemical bond containing deuterium, versus light hydrogen. The two stable isotopes of hydrogen can also be distinguished by using mass spectrometry
Mass spectrometry
Mass 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...

.

The triplet deuteron nucleon barely is bound at EB = , so all the higher energy states are not bound. The singlet deuteron is a virtual state, with a negative binding energy of . There is no such stable particle, but this virtual particle transiently exists during neutron-proton inelastic scattering, accounting for the unusually large neutron scattering cross-section of the proton.

Deuteron mass and radius


The nucleus of deuterium is called a deuteron. It has a mass of
The charge radius
Charge radius
The rms charge radius is a measure of the size of an atomic nucleus, particularly of a proton or a deuteron. It can be measured by the scattering of electrons by the nucleus and also inferred from the effects of finite nuclear size on electron energy levels as measured in atomic...

 of the deuteron is

Spin and energy


Deuterium is one of only four stable 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....

s with an odd number of protons and odd number of neutrons. Most odd-odd nuclei are unstable with respect to 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...

, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. Deuterium, however, benefits from having its proton and neutron coupled to a spin-1 state, which gives a stronger nuclear attraction; the corresponding spin-1 state does not exist in the two-neutron or two-proton system, due to the Pauli exclusion principle
Pauli exclusion principle
The Pauli exclusion principle is the quantum mechanical principle that no two identical fermions may occupy the same quantum state simultaneously. A more rigorous statement is that the total wave function for two identical fermions is anti-symmetric with respect to exchange of the particles...

 which would require one or the other identical particle with the same spin to have some other different quantum number, such as orbital angular momentum. But orbital angular momentum of either particle gives a lower binding energy
Binding energy
Binding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system typically has a lower potential energy than its constituent parts; this is what keeps the system together—often this means that energy is released upon the creation of a bound state...

 for the system, primarily due to increasing distance of the particles in the steep gradient of the nuclear force. In both cases, this causes the diproton
Diproton
A diproton is a hypothetical isotope of helium nucleus consisting of two protons and no neutrons, and is predicted to be less stable than 5He...

 and dineutron
Dineutron
A dineutron is a hypothetical particle consisting of two neutrons that was suggested to have a transitory existence in nuclear reactions produced by helions that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater...

 nucleus to be unstable.

The proton and neutron making up deuterium can be dissociated
Dissociation (chemistry)
Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner...

 through neutral current
Neutral current
Weak neutral current interactions are one of the ways in which subatomic particles can interact by means of the weak force. These interactions are mediated by the boson...

 interactions with neutrinos. The cross section
Cross section (physics)
A cross section is the effective area which governs the probability of some scattering or absorption event. Together with particle density and path length, it can be used to predict the total scattering probability via the Beer-Lambert law....

 for this interaction is comparatively large, and deuterium was successfully used as a neutrino target in the Sudbury Neutrino Observatory
Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a neutrino observatory located 6,800 feet underground in Vale Inco's Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large tank of heavy water. The detector turned on in May 1999,...

 experiment.

Isospin singlet state of the deuteron


Due to the similarity in mass and nuclear properties between the proton and neutron, they are sometimes considered as two symmetric types of the same object, a nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

. While only the proton has an electric charge, this is often negligible due of the weakness of the electromagnetic interaction relative to the strong nuclear interaction. The symmetry relating the proton and neutron is known as isospin
Isospin
In physics, and specifically, particle physics, isospin is a quantum number related to the strong interaction. This term was derived from isotopic spin, but the term is confusing as two isotopes of a nucleus have different numbers of nucleons; in contrast, rotations of isospin maintain the number...

 and denoted I (or sometimes T).

Isospin is an SU(2) symmetry, like ordinary 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,...

, so is completely analogous to it. The proton and neutron form an isospin doublet, with a "down" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 (↓) being a neutron, and an "up" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 (↑) being a proton.

A pair of nucleons can either be in an antisymmetric state of isospin called singlet, or in a symmetric state called triplet. In terms of the "down" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 and "up" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

, the singlet is

This is a nucleus with one proton and one neutron, i.e. a deuterium nucleus. The triplet is
and thus consists of three types of nuclei, which are supposed to be symmetric: a deuterium nucleus (actually a highly excited state
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....

 of it), a nucleus with two protons, and a nucleus with two neutrons. The latter two nuclei are not stable or nearly stable, and therefore so is this type of deuterium (meaning that it is indeed a highly excited state of deuterium).

Approximated wavefunction of the deuteron


The deuteron wavefunction must be antisymmetric if the isospin representation is used (since a proton and a neutron are not identical particles, the wavefunction
need not be antisymmetric in general). Apart from their isospin, the two nucleons also have spin and spatial distributions of their wavefunction. The latter is symmetric if the deuteron is symmetric under parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...

 (i.e. have an "even" or "positive" parity), and antisymmetric if the deuteron is antisymmetric under parity (i.e. have an "odd" or "negative" parity). The parity is fully determined by the total orbital angular momentum of the two nucleons: if it is even then the parity is even (positive), and if it is odd then the parity is odd (negative).

The deuteron, being an isospin singlet, is antisymmetric under nucleons exchange due to isospin, and therefore must be symmetric under the double exchange of their spin and location. Therefore it can be in either of the following two different states:
  • Symmetric spin and symmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (+1) from spin exchange and (+1) from parity (location exchange), for a total of (−1) as needed for antisymmetry.
  • Antisymmetric spin and antisymmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (−1) from spin exchange and (−1) from parity (location exchange), again for a total of (−1) as needed for antisymmetry.


In the first case the deuteron is a spin triplet, so that its total spin s is 1. It also has an even parity and therefore even orbital angular momentum l ; The lower its orbital angular momentum, the lower its energy. Therefore the lowest possible energy state has , .

In the second case the deuteron is a spin singlet, so that its total spin s is 0. It also has an odd parity and therefore odd orbital angular momentum l. Therefore the lowest possible energy state has , .

Since gives a stronger nuclear attraction, the deuterium ground state
Ground state
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state...

 is in the , state.

The same considerations lead to the possible states of an isospin triplet having , or , . Thus the state of lowest energy has , , higher than that of the isospin singlet.

The analysis just given is in fact only approximate, both because isospin is not an exact symmetry, and more importantly because the strong nuclear interaction between the two nucleons is related to angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...

 in spin-orbit interaction
Spin-orbit interaction
In quantum physics, the spin-orbit interaction is any interaction of a particle's spin with its motion. The first and best known example of this is that spin-orbit interaction causes shifts in an electron's atomic energy levels due to electromagnetic interaction between the electron's spin and...

 that mixes different s and l states. That is, s and l are not constant in time (they do not commute
Commutativity
In mathematics an operation is commutative if changing the order of the operands does not change the end result. It is a fundamental property of many binary operations, and many mathematical proofs depend on it...

 with the Hamiltonian
Hamiltonian (quantum mechanics)
In quantum mechanics, the Hamiltonian H, also Ȟ or Ĥ, is the operator corresponding to the total energy of the system. Its spectrum is the set of possible outcomes when one measures the total energy of a system...

), and over time a state such as , may become a state of , . Parity is still constant in time so these do not mix with odd l states (such as ). Therefore the quantum state of the deuterium is a superposition
Quantum superposition
Quantum superposition is a fundamental principle of quantum mechanics. It holds that a physical system exists in all its particular, theoretically possible states simultaneously; but, when measured, it gives a result corresponding to only one of the possible configurations.Mathematically, it...

 (a linear combination) of the , state and the , state, even though the first component is much bigger. Since the total angular momentum j is also a good quantum number
Quantum number
Quantum numbers describe values of conserved quantities in the dynamics of the quantum system. Perhaps the most peculiar aspect of quantum mechanics is the quantization of observable quantities. This is distinguished from classical mechanics where the values can range continuously...

 (it is a constant in time), both components must have the same j, and therefore . This is the total spin of the deuterium nucleus.

To summarize, the deuterium nucleus is antisymmetric in terms of isospin, and has spin 1 and even (+1) parity. The relative angular momentum of its nucleons l is not well defined, and the deuteron is a superposition of mostly with some .

Magnetic and electric multipoles


In order to find theoretically the deuterium magnetic dipole moment µ, one uses the formula for a nuclear magnetic moment
Nuclear magnetic moment
The nuclear magnetic moment is the magnetic moment of an atomic nucleus and arises from the spin of the protons and neutrons. It is mainly a magnetic dipole moment; the quadrupole moment does cause some small shifts in the hyperfine structure as well....


with
g(l) and g(s) are g-factors of the nucleons.

Since the proton and neutron have different values for g(l) and g(s), one must separate their contributions. Each gets half of the deuterium orbital angular momentum  and spin . One arrives at

where subscripts p and n stand for the proton and neutron, and .

By using the same identities as here and using the value , we arrive at the following result, in nuclear magneton units

For the , state , we obtain

For the , state , we obtain

The measured value of the deuterium magnetic dipole moment, is . This suggests that the state of the deuterium is indeed only approximately , state, and is actually a linear combination of (mostly) this state with , state.

The electric dipole is zero as usual
Shell model
In nuclear physics and nuclear chemistry, the nuclear shell model is a model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The first shell model was proposed by Dmitry Ivanenko in 1932...

.

The measured electric quadrupole
Quadrupole
A quadrupole or quadrapole is one of a sequence of configurations of—for example—electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure reflecting various orders of complexity.-Mathematical...

 of the deuterium is . While the order of magnitude is reasonable, since the deuterium radius is of order of 1 femtometer (see below) and its electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

 is e, the above model does not suffice for its computation. More specifically, the electric quadrupole does not get a contribution from the l =0 state (which is the dominant one) and does get a contribution from a term mixing the l =0 and the l =2 states, because the electric quadrupole operator does not commute with angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...

.
The latter contribution is dominant in the absence of a pure contribution, but cannot be calculated without knowing the exact spatial form of the nucleons wavefunction
Wavefunction
Not to be confused with the related concept of the Wave equationA wave function or wavefunction is a probability amplitude in quantum mechanics describing the quantum state of a particle and how it behaves. Typically, its values are complex numbers and, for a single particle, it is a function of...

 inside the deuterium.

Higher magnetic and electric multipole moments cannot be calculated by the above model, for similar reasons.

Applications




Deuterium has a number of commercial and scientific uses. These include:

Nuclear reactors


Deuterium is useful in nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

 reactions, especially in combination with tritium
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...

, because of the large reaction rate (or nuclear cross section
Nuclear cross section
The nuclear cross section of a nucleus is used to characterize the probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction...

) and high energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 yield of the D–T reaction. There is an even higher-yield D–

{{Stable Isotope
|isotope_name = Hydrogen-2
|isotope_filename = hydrogen-2.svg
|alternate_names = deuterium
|mass_number = 2
|symbol = H or D
|num_neutrons = 1
|num_protons = 1
|abundance = 0.015%
|mass = 2.01410178
|spin = 1+
|excess_energy = 13135.720
|error1 = 0.001
|binding_energy = 2224.52
|error2 = 0.20
}}

Deuterium, also called heavy hydrogen, is one of two stable isotopes of
hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

. It has a natural abundance
Natural abundance
In chemistry, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table...

 in Earth's oceans of about one atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

 in {{val|6420}} of hydrogen ({{val|p=~|156.25|ul=ppm}} on an atom basis). Deuterium accounts for approximately 0.0156% (or on a mass basis: 0.0312%) of all naturally occurring hydrogen in Earth's oceans, while the most common isotope (hydrogen-1
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 or protium) accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another (see VSMOW).

The nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 of deuterium, called a deuteron, contains one proton
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....

 and one neutron
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...

, whereas the far more common hydrogen isotope, protium, has no neutron in the nucleus. The deuterium isotope's name is formed from the Greek deuteros meaning "second", to denote the two particles composing the nucleus. Deuterium was discovered and named in 1931 by Harold Urey
Harold Urey
Harold Clayton Urey was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934...

, earning him a Nobel Prize in 1934 after the discovery of the neutron in 1932 made the structure of deuterium obvious. Soon after deuterium's discovery, Urey and others produced samples of water in which deuterium has been highly concentrated with respect to protium, a substance popularly known as heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

.

Because deuterium is destroyed in the interiors of stars faster than it is produced, and because other natural processes are thought to produce only an insignificant amount of deuterium, it is presently thought that nearly all deuterium found in nature was produced in the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 13.7 billion years ago, and that the basic or primordial ratio of hydrogen-1 (protium) to deuterium (about 26 atoms of deuterium per million hydrogen) has its origin from that time. This is the ratio found in the gas giant planets, such as Jupiter. However, different astronomical bodies are found to have different ratios of deuterium to hydrogen-1, and this is thought to be as a result of natural isotope separation processes that occur from solar heating of ices in comets. Like the water-cycle in Earth's weather, such heating processes may enrich deuterium with respect to protium. In fact, the discovery of deuterium/protium ratios in a number of comets very simlar to the mean ratio in Earth's oceans, has led to theories that much of Earth's ocean water has a cometary origin.

Deuterium/protium ratios thus continue to be an active topic of research in both astronomy and climatology.

Chemical symbol



Deuterium is frequently represented by the chemical symbol
Chemical symbol
A chemical symbol is a 1- or 2-letter internationally agreed code for a chemical element, usually derived from the name of the element, often in Latin. Only the first letter is capitalised...

 D. Since it is an isotope of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 with mass number
Mass number
The mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...

 2, it is also represented by {{SimpleNuclide|Hydrogen|2}}. IUPAC allows both D and {{SimpleNuclide|Hydrogen|2}}, although {{SimpleNuclide|Hydrogen|2}} is preferred. A distinct chemical symbol is used for convenience because of the isotope's common use in various scientific processes. Also, its large mass difference with protium ({{SimpleNuclide|Hydrogen|1}}) (deuterium has a mass of {{val|2.014102|ul=u}}, compared to the mean
Mean
In statistics, mean has two related meanings:* the arithmetic mean .* the expected value of a random variable, which is also called the population mean....

 hydrogen atomic weight
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...

 of {{val|1.007947|u=u}}, and protium's mass of {{val|1.007825|u=u}}) confers non-negligible chemical dissimilarities with protium-containing compounds, whereas the isotope weight ratios within other chemical elements are largely insignificant in this regard.

Natural abundance


{{Main|Big Bang nucleosynthesis}}
Deuterium occurs in trace amounts naturally as deuterium gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

, written {{SimpleNuclide|Hydrogen|2}}2 or D2, but most natural occurrence in the universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 is bonded with a typical {{SimpleNuclide|Hydrogen|1}} atom, a gas called hydrogen deuteride
Hydrogen deuteride
Hydrogen deuteride is a diatomic molecule composed of the two isotopes of hydrogen: the majority isotope 1H protium and 2H deuterium. Its molecular formula is HD.- Availability in nature :...

 (HD or {{SimpleNuclide|Hydrogen|1}}{{SimpleNuclide|Hydrogen|2}}).

The natural deuterium abundance seems to be a very similar fraction of hydrogen, wherever hydrogen is found. Thus, the existence of deuterium at a low but constant fraction in all hydrogen, is one of the arguments in favor of the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 theory over the Steady State theory
Steady State theory
In cosmology, the Steady State theory is a model developed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others as an alternative to the Big Bang theory...

 of the universe. It is estimated that the abundances of deuterium have not evolved significantly since their production about {{val|13.7|ul=bya}}.

Deuterium abundance on Jupiter has been directly measured at 26 atoms D per million hydrogens by the Galileo entry probe; ISO-SWS observations find 22 atoms of D per million H atoms in Jupiter. and this abundance is thought to represent close to the primordial solar system ratio. This is about 17% of the terrestrial deuterium-to-hydrogen ratio of 156 deuterium atoms per million hydrogen atoms.

Cometary bodies such as Comet Hale Bopp and Halley's Comet have been measured to contain relatively more deuterium (about 200 atoms D per million hydrogens), ratios which are enriched with respect to the presumed protosolar nebula ratio, probably due to heating, and which are similar to the ratios found in Earth seawater. The recent measurement of deuterium amounts of 161 atoms D per million hydrogen in Comet 103P/Hartley
103P/Hartley
Comet Hartley 2, designated as 103P/Hartley by the Minor Planet Center, is a small periodic comet with an orbital period of 6.46 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit, Siding Spring Observatory, Australia...

 (a former Kuiper belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...

 object), a ratio almost exactly that in Earth's oceans, emphasizes the theory that Earth's surface water may be largely comet-derived.

There is thought to be little deuterium in the interior of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and other stars, as at temperatures there nuclear fusion reactions that consume deuterium happen much faster than the proton-proton reaction that creates deuterium. However, it continues to persist in the outer solar atmosphere at roughly the same concentration as in Jupiter.

The existence of deuterium on Earth, elsewhere in the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 (as confirmed by planetary probes), and in the spectra of star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s, is an important datum in cosmology
Physical cosmology
Physical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...

. Gamma radiation from ordinary nuclear fusion dissociates deuterium into protons and neutrons, and there are no known natural processes other than the Big Bang nucleosynthesis
Big Bang nucleosynthesis
In physical cosmology, Big Bang nucleosynthesis refers to the production of nuclei other than those of H-1 during the early phases of the universe...

, which might have produced deuterium at anything close to the observed natural abundance of deuterium (deuterium is produced by the rare cluster decay
Cluster decay
Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy...

, and occasional absorption of naturally occurring neutrons by light hydrogen, but these are trivial sources).

Concentrating natural abundance deuterium


Deuterium is concentrated for industrial, scientific and military purposes as heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

 from ordinary water. The world's leading supplier of deuterium was Atomic Energy of Canada Limited
Atomic Energy of Canada Limited
Atomic Energy of Canada Limited or AECL is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory...

, in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, until 1997, when the last heavy water plant was shut down. Canada uses heavy water as a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

 for the operation of the CANDU reactor
CANDU reactor
The CANDU reactor is a Canadian-invented, pressurized heavy water reactor. The acronym refers to its deuterium-oxide moderator and its use of uranium fuel...

 design.

Physical properties


The physical properties of deuterium compounds can exhibit significant kinetic isotope effect
Kinetic isotope effect
The kinetic isotope effect is the ratio of reaction rates of two different isotopically labeled molecules in a chemical reaction. It is also called "isotope fractionation," although this term is somewhat broader in meaning...

s and other physical and chemical property differences from the hydrogen analogs; for example, D2O is more viscous
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 than H2O
H2O
H2O is the chemical formula for water and is also used as an abbreviation for the word "water". H2O or H2O It may also refer to:* H2O , a punk band**H2O , their self-titled debut album...

.
Chemically, deuterium behaves similarly to ordinary hydrogen, but there are differences in bond energy and length for compounds of heavy hydrogen isotopes which are larger than the isotopic differences in any other element. Bonds involving deuterium and tritium
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...

 are somewhat stronger than the corresponding bonds in hydrogen, and these differences are enough to make significant changes in biological reactions.

Deuterium can replace the normal hydrogen in water molecules to form heavy water (D2O), which is about 10.6% denser than normal water (enough that ice made from it sinks in ordinary water). Heavy water is slightly toxic in eukaryotic animals, with 25% substitution of the body water causing cell division problems and sterility, and 50% substitution causing death by cytotoxic syndrome (bone marrow failure and gastrointestinal lining failure). Prokaryotic organisms, however, can survive and grow in pure heavy water (though they grow more slowly). Consumption of heavy water does not pose a health threat to humans, it is estimated that a {{val|70|ul=kg}} person might drink 4.8 liters of heavy water without serious consequences. Small doses of heavy water (a few grams in humans, containing an amount of deuterium comparable to that normally present in the body) are routinely used as harmless metabolic tracers in humans and animals.

Quantum properties


The deuteron has spin +1 ("triplet") and is thus a boson
Boson
In particle physics, bosons are subatomic particles that obey Bose–Einstein statistics. Several bosons can occupy the same quantum state. The word boson derives from the name of Satyendra Nath Bose....

. The NMR
Nuclear magnetic resonance
Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...

 frequency of deuterium is significantly different from common light hydrogen. Infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...

 also easily differentiates many deuterated compounds, due to the large difference in IR absorption frequency seen in the vibration of a chemical bond containing deuterium, versus light hydrogen. The two stable isotopes of hydrogen can also be distinguished by using mass spectrometry
Mass spectrometry
Mass 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...

.

The triplet deuteron nucleon barely is bound at EB = {{val|2.23|u=MeV}}, so all the higher energy states are not bound. The singlet deuteron is a virtual state, with a negative binding energy of {{val|p=~|60|u=keV}}. There is no such stable particle, but this virtual particle transiently exists during neutron-proton inelastic scattering, accounting for the unusually large neutron scattering cross-section of the proton.

Deuteron mass and radius


The nucleus of deuterium is called a deuteron. It has a mass of {{val|2.013553212724|(78)|u=u}}
The charge radius
Charge radius
The rms charge radius is a measure of the size of an atomic nucleus, particularly of a proton or a deuteron. It can be measured by the scattering of electrons by the nucleus and also inferred from the effects of finite nuclear size on electron energy levels as measured in atomic...

 of the deuteron is {{val|2.1402|(28)|ul=fm}}

Spin and energy


Deuterium is one of only four stable 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....

s with an odd number of protons and odd number of neutrons. ({{SimpleNuclide|Hydrogen|2}}, {{SimpleNuclide|Lithium|6}}, {{SimpleNuclide|Boron|10}}, {{SimpleNuclide|Nitrogen|14}}; also, the long-lived radioactive nuclides {{SimpleNuclide|Potassium|40}}, {{SimpleNuclide|Vanadium|50}}, {{SimpleNuclide|Lanthanum|138}}, {{SimpleNuclide|Tantalum|180m}} occur naturally.) Most odd-odd nuclei are unstable with respect to 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...

, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. Deuterium, however, benefits from having its proton and neutron coupled to a spin-1 state, which gives a stronger nuclear attraction; the corresponding spin-1 state does not exist in the two-neutron or two-proton system, due to the Pauli exclusion principle
Pauli exclusion principle
The Pauli exclusion principle is the quantum mechanical principle that no two identical fermions may occupy the same quantum state simultaneously. A more rigorous statement is that the total wave function for two identical fermions is anti-symmetric with respect to exchange of the particles...

 which would require one or the other identical particle with the same spin to have some other different quantum number, such as orbital angular momentum. But orbital angular momentum of either particle gives a lower binding energy
Binding energy
Binding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system typically has a lower potential energy than its constituent parts; this is what keeps the system together—often this means that energy is released upon the creation of a bound state...

 for the system, primarily due to increasing distance of the particles in the steep gradient of the nuclear force. In both cases, this causes the diproton
Diproton
A diproton is a hypothetical isotope of helium nucleus consisting of two protons and no neutrons, and is predicted to be less stable than 5He...

 and dineutron
Dineutron
A dineutron is a hypothetical particle consisting of two neutrons that was suggested to have a transitory existence in nuclear reactions produced by helions that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater...

 nucleus to be unstable.

The proton and neutron making up deuterium can be dissociated
Dissociation (chemistry)
Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner...

 through neutral current
Neutral current
Weak neutral current interactions are one of the ways in which subatomic particles can interact by means of the weak force. These interactions are mediated by the boson...

 interactions with neutrinos. The cross section
Cross section (physics)
A cross section is the effective area which governs the probability of some scattering or absorption event. Together with particle density and path length, it can be used to predict the total scattering probability via the Beer-Lambert law....

 for this interaction is comparatively large, and deuterium was successfully used as a neutrino target in the Sudbury Neutrino Observatory
Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a neutrino observatory located 6,800 feet underground in Vale Inco's Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large tank of heavy water. The detector turned on in May 1999,...

 experiment.

Isospin singlet state of the deuteron


Due to the similarity in mass and nuclear properties between the proton and neutron, they are sometimes considered as two symmetric types of the same object, a nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

. While only the proton has an electric charge, this is often negligible due of the weakness of the electromagnetic interaction relative to the strong nuclear interaction. The symmetry relating the proton and neutron is known as isospin
Isospin
In physics, and specifically, particle physics, isospin is a quantum number related to the strong interaction. This term was derived from isotopic spin, but the term is confusing as two isotopes of a nucleus have different numbers of nucleons; in contrast, rotations of isospin maintain the number...

 and denoted I (or sometimes T).

Isospin is an SU(2) symmetry, like ordinary 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,...

, so is completely analogous to it. The proton and neutron form an isospin doublet, with a "down" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 (↓) being a neutron, and an "up" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 (↑) being a proton.

A pair of nucleons can either be in an antisymmetric state of isospin called singlet, or in a symmetric state called triplet. In terms of the "down" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 and "up" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

, the singlet is

This is a nucleus with one proton and one neutron, i.e. a deuterium nucleus. The triplet is
and thus consists of three types of nuclei, which are supposed to be symmetric: a deuterium nucleus (actually a highly excited state
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....

 of it), a nucleus with two protons, and a nucleus with two neutrons. The latter two nuclei are not stable or nearly stable, and therefore so is this type of deuterium (meaning that it is indeed a highly excited state of deuterium).

Approximated wavefunction of the deuteron


The deuteron wavefunction must be antisymmetric if the isospin representation is used (since a proton and a neutron are not identical particles, the wavefunction
need not be antisymmetric in general). Apart from their isospin, the two nucleons also have spin and spatial distributions of their wavefunction. The latter is symmetric if the deuteron is symmetric under parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...

 (i.e. have an "even" or "positive" parity), and antisymmetric if the deuteron is antisymmetric under parity (i.e. have an "odd" or "negative" parity). The parity is fully determined by the total orbital angular momentum of the two nucleons: if it is even then the parity is even (positive), and if it is odd then the parity is odd (negative).

The deuteron, being an isospin singlet, is antisymmetric under nucleons exchange due to isospin, and therefore must be symmetric under the double exchange of their spin and location. Therefore it can be in either of the following two different states:
  • Symmetric spin and symmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (+1) from spin exchange and (+1) from parity (location exchange), for a total of (−1) as needed for antisymmetry.
  • Antisymmetric spin and antisymmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (−1) from spin exchange and (−1) from parity (location exchange), again for a total of (−1) as needed for antisymmetry.


In the first case the deuteron is a spin triplet, so that its total spin s is 1. It also has an even parity and therefore even orbital angular momentum l ; The lower its orbital angular momentum, the lower its energy. Therefore the lowest possible energy state has {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}}.

In the second case the deuteron is a spin singlet, so that its total spin s is 0. It also has an odd parity and therefore odd orbital angular momentum l. Therefore the lowest possible energy state has {{nowrap|s {{=}} 0}}, {{nowrap|l {{=}} 1}}.

Since {{nowrap|s {{=}} 1}} gives a stronger nuclear attraction, the deuterium ground state
Ground state
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state...

 is in the {{nowrap|s {{=}}1}}, {{nowrap|l {{=}} 0}} state.

The same considerations lead to the possible states of an isospin triplet having {{nowrap|s {{=}} 0}}, {{nowrap|l {{=}} even}} or {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} odd}}. Thus the state of lowest energy has {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 1}}, higher than that of the isospin singlet.

The analysis just given is in fact only approximate, both because isospin is not an exact symmetry, and more importantly because the strong nuclear interaction between the two nucleons is related to angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...

 in spin-orbit interaction
Spin-orbit interaction
In quantum physics, the spin-orbit interaction is any interaction of a particle's spin with its motion. The first and best known example of this is that spin-orbit interaction causes shifts in an electron's atomic energy levels due to electromagnetic interaction between the electron's spin and...

 that mixes different s and l states. That is, s and l are not constant in time (they do not commute
Commutativity
In mathematics an operation is commutative if changing the order of the operands does not change the end result. It is a fundamental property of many binary operations, and many mathematical proofs depend on it...

 with the Hamiltonian
Hamiltonian (quantum mechanics)
In quantum mechanics, the Hamiltonian H, also Ȟ or Ĥ, is the operator corresponding to the total energy of the system. Its spectrum is the set of possible outcomes when one measures the total energy of a system...

), and over time a state such as {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} may become a state of {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}}. Parity is still constant in time so these do not mix with odd l states (such as {{nowrap|s {{=}} 0}}, {{nowrap|l {{=}} 1}}). Therefore the quantum state of the deuterium is a superposition
Quantum superposition
Quantum superposition is a fundamental principle of quantum mechanics. It holds that a physical system exists in all its particular, theoretically possible states simultaneously; but, when measured, it gives a result corresponding to only one of the possible configurations.Mathematically, it...

 (a linear combination) of the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} state and the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}} state, even though the first component is much bigger. Since the total angular momentum j is also a good quantum number
Quantum number
Quantum numbers describe values of conserved quantities in the dynamics of the quantum system. Perhaps the most peculiar aspect of quantum mechanics is the quantization of observable quantities. This is distinguished from classical mechanics where the values can range continuously...

 (it is a constant in time), both components must have the same j, and therefore {{nowrap|j {{=}} 1}}. This is the total spin of the deuterium nucleus.

To summarize, the deuterium nucleus is antisymmetric in terms of isospin, and has spin 1 and even (+1) parity. The relative angular momentum of its nucleons l is not well defined, and the deuteron is a superposition of mostly {{nowrap|l {{=}} 0}} with some {{nowrap|l {{=}} 2}}.

Magnetic and electric multipoles


In order to find theoretically the deuterium magnetic dipole moment µ, one uses the formula for a nuclear magnetic moment
Nuclear magnetic moment
The nuclear magnetic moment is the magnetic moment of an atomic nucleus and arises from the spin of the protons and neutrons. It is mainly a magnetic dipole moment; the quadrupole moment does cause some small shifts in the hyperfine structure as well....


with
g(l) and g(s) are g-factors of the nucleons.

Since the proton and neutron have different values for g(l) and g(s), one must separate their contributions. Each gets half of the deuterium orbital angular momentum  and spin . One arrives at

where subscripts p and n stand for the proton and neutron, and {{nowrap|g(l)n {{=}} 0}}.

By using the same identities as here and using the value {{nowrap|g(l)p {{=}} {{val|1|ul=µN}}}}, we arrive at the following result, in nuclear magneton units

For the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} state ({{nowrap|j {{=}} 1}}), we obtain

For the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}} state ({{nowrap|j {{=}} 1}}), we obtain

The measured value of the deuterium magnetic dipole moment, is {{val|0.857|u=µN}}. This suggests that the state of the deuterium is indeed only approximately {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} state, and is actually a linear combination of (mostly) this state with {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}} state.

The electric dipole is zero as usual
Shell model
In nuclear physics and nuclear chemistry, the nuclear shell model is a model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The first shell model was proposed by Dmitry Ivanenko in 1932...

.

The measured electric quadrupole
Quadrupole
A quadrupole or quadrapole is one of a sequence of configurations of—for example—electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure reflecting various orders of complexity.-Mathematical...

 of the deuterium is {{val|0.2859|u=e
Elementary charge
The elementary charge, usually denoted as e, is the electric charge carried by a single proton, or equivalently, the absolute value of the electric charge carried by a single electron. This elementary charge is a fundamental physical constant. To avoid confusion over its sign, e is sometimes called...

·fm2}}. While the order of magnitude is reasonable, since the deuterium radius is of order of 1 femtometer (see below) and its electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

 is e, the above model does not suffice for its computation. More specifically, the electric quadrupole does not get a contribution from the l =0 state (which is the dominant one) and does get a contribution from a term mixing the l =0 and the l =2 states, because the electric quadrupole operator does not commute with angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...

.
The latter contribution is dominant in the absence of a pure {{nowrap|l {{=}} 0}} contribution, but cannot be calculated without knowing the exact spatial form of the nucleons wavefunction
Wavefunction
Not to be confused with the related concept of the Wave equationA wave function or wavefunction is a probability amplitude in quantum mechanics describing the quantum state of a particle and how it behaves. Typically, its values are complex numbers and, for a single particle, it is a function of...

 inside the deuterium.

Higher magnetic and electric multipole moments cannot be calculated by the above model, for similar reasons.

Applications




Deuterium has a number of commercial and scientific uses. These include:

Nuclear reactors


Deuterium is useful in nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

 reactions, especially in combination with tritium
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...

, because of the large reaction rate (or nuclear cross section
Nuclear cross section
The nuclear cross section of a nucleus is used to characterize the probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction...

) and high energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 yield of the D–T reaction. There is an even higher-yield D–

{{Stable Isotope
|isotope_name = Hydrogen-2
|isotope_filename = hydrogen-2.svg
|alternate_names = deuterium
|mass_number = 2
|symbol = H or D
|num_neutrons = 1
|num_protons = 1
|abundance = 0.015%
|mass = 2.01410178
|spin = 1+
|excess_energy = 13135.720
|error1 = 0.001
|binding_energy = 2224.52
|error2 = 0.20
}}

Deuterium, also called heavy hydrogen, is one of two stable isotopes of
hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

. It has a natural abundance
Natural abundance
In chemistry, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table...

 in Earth's oceans of about one atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

 in {{val|6420}} of hydrogen ({{val|p=~|156.25|ul=ppm}} on an atom basis). Deuterium accounts for approximately 0.0156% (or on a mass basis: 0.0312%) of all naturally occurring hydrogen in Earth's oceans, while the most common isotope (hydrogen-1
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 or protium) accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another (see VSMOW).

The nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 of deuterium, called a deuteron, contains one proton
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....

 and one neutron
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...

, whereas the far more common hydrogen isotope, protium, has no neutron in the nucleus. The deuterium isotope's name is formed from the Greek deuteros meaning "second", to denote the two particles composing the nucleus. Deuterium was discovered and named in 1931 by Harold Urey
Harold Urey
Harold Clayton Urey was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934...

, earning him a Nobel Prize in 1934 after the discovery of the neutron in 1932 made the structure of deuterium obvious. Soon after deuterium's discovery, Urey and others produced samples of water in which deuterium has been highly concentrated with respect to protium, a substance popularly known as heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

.

Because deuterium is destroyed in the interiors of stars faster than it is produced, and because other natural processes are thought to produce only an insignificant amount of deuterium, it is presently thought that nearly all deuterium found in nature was produced in the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 13.7 billion years ago, and that the basic or primordial ratio of hydrogen-1 (protium) to deuterium (about 26 atoms of deuterium per million hydrogen) has its origin from that time. This is the ratio found in the gas giant planets, such as Jupiter. However, different astronomical bodies are found to have different ratios of deuterium to hydrogen-1, and this is thought to be as a result of natural isotope separation processes that occur from solar heating of ices in comets. Like the water-cycle in Earth's weather, such heating processes may enrich deuterium with respect to protium. In fact, the discovery of deuterium/protium ratios in a number of comets very simlar to the mean ratio in Earth's oceans, has led to theories that much of Earth's ocean water has a cometary origin.

Deuterium/protium ratios thus continue to be an active topic of research in both astronomy and climatology.

Chemical symbol



Deuterium is frequently represented by the chemical symbol
Chemical symbol
A chemical symbol is a 1- or 2-letter internationally agreed code for a chemical element, usually derived from the name of the element, often in Latin. Only the first letter is capitalised...

 D. Since it is an isotope of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 with mass number
Mass number
The mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...

 2, it is also represented by {{SimpleNuclide|Hydrogen|2}}. IUPAC allows both D and {{SimpleNuclide|Hydrogen|2}}, although {{SimpleNuclide|Hydrogen|2}} is preferred. A distinct chemical symbol is used for convenience because of the isotope's common use in various scientific processes. Also, its large mass difference with protium ({{SimpleNuclide|Hydrogen|1}}) (deuterium has a mass of {{val|2.014102|ul=u}}, compared to the mean
Mean
In statistics, mean has two related meanings:* the arithmetic mean .* the expected value of a random variable, which is also called the population mean....

 hydrogen atomic weight
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...

 of {{val|1.007947|u=u}}, and protium's mass of {{val|1.007825|u=u}}) confers non-negligible chemical dissimilarities with protium-containing compounds, whereas the isotope weight ratios within other chemical elements are largely insignificant in this regard.

Natural abundance


{{Main|Big Bang nucleosynthesis}}
Deuterium occurs in trace amounts naturally as deuterium gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

, written {{SimpleNuclide|Hydrogen|2}}2 or D2, but most natural occurrence in the universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 is bonded with a typical {{SimpleNuclide|Hydrogen|1}} atom, a gas called hydrogen deuteride
Hydrogen deuteride
Hydrogen deuteride is a diatomic molecule composed of the two isotopes of hydrogen: the majority isotope 1H protium and 2H deuterium. Its molecular formula is HD.- Availability in nature :...

 (HD or {{SimpleNuclide|Hydrogen|1}}{{SimpleNuclide|Hydrogen|2}}).

The natural deuterium abundance seems to be a very similar fraction of hydrogen, wherever hydrogen is found. Thus, the existence of deuterium at a low but constant fraction in all hydrogen, is one of the arguments in favor of the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 theory over the Steady State theory
Steady State theory
In cosmology, the Steady State theory is a model developed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others as an alternative to the Big Bang theory...

 of the universe. It is estimated that the abundances of deuterium have not evolved significantly since their production about {{val|13.7|ul=bya}}.

Deuterium abundance on Jupiter has been directly measured at 26 atoms D per million hydrogens by the Galileo entry probe; ISO-SWS observations find 22 atoms of D per million H atoms in Jupiter. and this abundance is thought to represent close to the primordial solar system ratio. This is about 17% of the terrestrial deuterium-to-hydrogen ratio of 156 deuterium atoms per million hydrogen atoms.

Cometary bodies such as Comet Hale Bopp and Halley's Comet have been measured to contain relatively more deuterium (about 200 atoms D per million hydrogens), ratios which are enriched with respect to the presumed protosolar nebula ratio, probably due to heating, and which are similar to the ratios found in Earth seawater. The recent measurement of deuterium amounts of 161 atoms D per million hydrogen in Comet 103P/Hartley
103P/Hartley
Comet Hartley 2, designated as 103P/Hartley by the Minor Planet Center, is a small periodic comet with an orbital period of 6.46 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit, Siding Spring Observatory, Australia...

 (a former Kuiper belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...

 object), a ratio almost exactly that in Earth's oceans, emphasizes the theory that Earth's surface water may be largely comet-derived.

There is thought to be little deuterium in the interior of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and other stars, as at temperatures there nuclear fusion reactions that consume deuterium happen much faster than the proton-proton reaction that creates deuterium. However, it continues to persist in the outer solar atmosphere at roughly the same concentration as in Jupiter.

The existence of deuterium on Earth, elsewhere in the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 (as confirmed by planetary probes), and in the spectra of star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s, is an important datum in cosmology
Physical cosmology
Physical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...

. Gamma radiation from ordinary nuclear fusion dissociates deuterium into protons and neutrons, and there are no known natural processes other than the Big Bang nucleosynthesis
Big Bang nucleosynthesis
In physical cosmology, Big Bang nucleosynthesis refers to the production of nuclei other than those of H-1 during the early phases of the universe...

, which might have produced deuterium at anything close to the observed natural abundance of deuterium (deuterium is produced by the rare cluster decay
Cluster decay
Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy...

, and occasional absorption of naturally occurring neutrons by light hydrogen, but these are trivial sources).

Concentrating natural abundance deuterium


Deuterium is concentrated for industrial, scientific and military purposes as heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

 from ordinary water. The world's leading supplier of deuterium was Atomic Energy of Canada Limited
Atomic Energy of Canada Limited
Atomic Energy of Canada Limited or AECL is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory...

, in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, until 1997, when the last heavy water plant was shut down. Canada uses heavy water as a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

 for the operation of the CANDU reactor
CANDU reactor
The CANDU reactor is a Canadian-invented, pressurized heavy water reactor. The acronym refers to its deuterium-oxide moderator and its use of uranium fuel...

 design.

Physical properties


The physical properties of deuterium compounds can exhibit significant kinetic isotope effect
Kinetic isotope effect
The kinetic isotope effect is the ratio of reaction rates of two different isotopically labeled molecules in a chemical reaction. It is also called "isotope fractionation," although this term is somewhat broader in meaning...

s and other physical and chemical property differences from the hydrogen analogs; for example, D2O is more viscous
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 than H2O
H2O
H2O is the chemical formula for water and is also used as an abbreviation for the word "water". H2O or H2O It may also refer to:* H2O , a punk band**H2O , their self-titled debut album...

.
Chemically, deuterium behaves similarly to ordinary hydrogen, but there are differences in bond energy and length for compounds of heavy hydrogen isotopes which are larger than the isotopic differences in any other element. Bonds involving deuterium and tritium
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...

 are somewhat stronger than the corresponding bonds in hydrogen, and these differences are enough to make significant changes in biological reactions.

Deuterium can replace the normal hydrogen in water molecules to form heavy water (D2O), which is about 10.6% denser than normal water (enough that ice made from it sinks in ordinary water). Heavy water is slightly toxic in eukaryotic animals, with 25% substitution of the body water causing cell division problems and sterility, and 50% substitution causing death by cytotoxic syndrome (bone marrow failure and gastrointestinal lining failure). Prokaryotic organisms, however, can survive and grow in pure heavy water (though they grow more slowly). Consumption of heavy water does not pose a health threat to humans, it is estimated that a {{val|70|ul=kg}} person might drink 4.8 liters of heavy water without serious consequences. Small doses of heavy water (a few grams in humans, containing an amount of deuterium comparable to that normally present in the body) are routinely used as harmless metabolic tracers in humans and animals.

Quantum properties


The deuteron has spin +1 ("triplet") and is thus a boson
Boson
In particle physics, bosons are subatomic particles that obey Bose–Einstein statistics. Several bosons can occupy the same quantum state. The word boson derives from the name of Satyendra Nath Bose....

. The NMR
Nuclear magnetic resonance
Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...

 frequency of deuterium is significantly different from common light hydrogen. Infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...

 also easily differentiates many deuterated compounds, due to the large difference in IR absorption frequency seen in the vibration of a chemical bond containing deuterium, versus light hydrogen. The two stable isotopes of hydrogen can also be distinguished by using mass spectrometry
Mass spectrometry
Mass 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...

.

The triplet deuteron nucleon barely is bound at EB = {{val|2.23|u=MeV}}, so all the higher energy states are not bound. The singlet deuteron is a virtual state, with a negative binding energy of {{val|p=~|60|u=keV}}. There is no such stable particle, but this virtual particle transiently exists during neutron-proton inelastic scattering, accounting for the unusually large neutron scattering cross-section of the proton.

Deuteron mass and radius


The nucleus of deuterium is called a deuteron. It has a mass of {{val|2.013553212724|(78)|u=u}}
The charge radius
Charge radius
The rms charge radius is a measure of the size of an atomic nucleus, particularly of a proton or a deuteron. It can be measured by the scattering of electrons by the nucleus and also inferred from the effects of finite nuclear size on electron energy levels as measured in atomic...

 of the deuteron is {{val|2.1402|(28)|ul=fm}}

Spin and energy


Deuterium is one of only four stable 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....

s with an odd number of protons and odd number of neutrons. ({{SimpleNuclide|Hydrogen|2}}, {{SimpleNuclide|Lithium|6}}, {{SimpleNuclide|Boron|10}}, {{SimpleNuclide|Nitrogen|14}}; also, the long-lived radioactive nuclides {{SimpleNuclide|Potassium|40}}, {{SimpleNuclide|Vanadium|50}}, {{SimpleNuclide|Lanthanum|138}}, {{SimpleNuclide|Tantalum|180m}} occur naturally.) Most odd-odd nuclei are unstable with respect to 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...

, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. Deuterium, however, benefits from having its proton and neutron coupled to a spin-1 state, which gives a stronger nuclear attraction; the corresponding spin-1 state does not exist in the two-neutron or two-proton system, due to the Pauli exclusion principle
Pauli exclusion principle
The Pauli exclusion principle is the quantum mechanical principle that no two identical fermions may occupy the same quantum state simultaneously. A more rigorous statement is that the total wave function for two identical fermions is anti-symmetric with respect to exchange of the particles...

 which would require one or the other identical particle with the same spin to have some other different quantum number, such as orbital angular momentum. But orbital angular momentum of either particle gives a lower binding energy
Binding energy
Binding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system typically has a lower potential energy than its constituent parts; this is what keeps the system together—often this means that energy is released upon the creation of a bound state...

 for the system, primarily due to increasing distance of the particles in the steep gradient of the nuclear force. In both cases, this causes the diproton
Diproton
A diproton is a hypothetical isotope of helium nucleus consisting of two protons and no neutrons, and is predicted to be less stable than 5He...

 and dineutron
Dineutron
A dineutron is a hypothetical particle consisting of two neutrons that was suggested to have a transitory existence in nuclear reactions produced by helions that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater...

 nucleus to be unstable.

The proton and neutron making up deuterium can be dissociated
Dissociation (chemistry)
Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner...

 through neutral current
Neutral current
Weak neutral current interactions are one of the ways in which subatomic particles can interact by means of the weak force. These interactions are mediated by the boson...

 interactions with neutrinos. The cross section
Cross section (physics)
A cross section is the effective area which governs the probability of some scattering or absorption event. Together with particle density and path length, it can be used to predict the total scattering probability via the Beer-Lambert law....

 for this interaction is comparatively large, and deuterium was successfully used as a neutrino target in the Sudbury Neutrino Observatory
Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a neutrino observatory located 6,800 feet underground in Vale Inco's Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large tank of heavy water. The detector turned on in May 1999,...

 experiment.

Isospin singlet state of the deuteron


Due to the similarity in mass and nuclear properties between the proton and neutron, they are sometimes considered as two symmetric types of the same object, a nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

. While only the proton has an electric charge, this is often negligible due of the weakness of the electromagnetic interaction relative to the strong nuclear interaction. The symmetry relating the proton and neutron is known as isospin
Isospin
In physics, and specifically, particle physics, isospin is a quantum number related to the strong interaction. This term was derived from isotopic spin, but the term is confusing as two isotopes of a nucleus have different numbers of nucleons; in contrast, rotations of isospin maintain the number...

 and denoted I (or sometimes T).

Isospin is an SU(2) symmetry, like ordinary 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,...

, so is completely analogous to it. The proton and neutron form an isospin doublet, with a "down" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 (↓) being a neutron, and an "up" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 (↑) being a proton.

A pair of nucleons can either be in an antisymmetric state of isospin called singlet, or in a symmetric state called triplet. In terms of the "down" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

 and "up" state
Spin-½
In quantum mechanics, spin is an intrinsic property of all elementary particles. Fermions, the particles that constitute ordinary matter, have half-integer spin. Spin-½ particles constitute an important subset of such fermions. All known elementary fermions have a spin of ½.- Overview :Particles...

, the singlet is

This is a nucleus with one proton and one neutron, i.e. a deuterium nucleus. The triplet is
and thus consists of three types of nuclei, which are supposed to be symmetric: a deuterium nucleus (actually a highly excited state
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....

 of it), a nucleus with two protons, and a nucleus with two neutrons. The latter two nuclei are not stable or nearly stable, and therefore so is this type of deuterium (meaning that it is indeed a highly excited state of deuterium).

Approximated wavefunction of the deuteron


The deuteron wavefunction must be antisymmetric if the isospin representation is used (since a proton and a neutron are not identical particles, the wavefunction
need not be antisymmetric in general). Apart from their isospin, the two nucleons also have spin and spatial distributions of their wavefunction. The latter is symmetric if the deuteron is symmetric under parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...

 (i.e. have an "even" or "positive" parity), and antisymmetric if the deuteron is antisymmetric under parity (i.e. have an "odd" or "negative" parity). The parity is fully determined by the total orbital angular momentum of the two nucleons: if it is even then the parity is even (positive), and if it is odd then the parity is odd (negative).

The deuteron, being an isospin singlet, is antisymmetric under nucleons exchange due to isospin, and therefore must be symmetric under the double exchange of their spin and location. Therefore it can be in either of the following two different states:
  • Symmetric spin and symmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (+1) from spin exchange and (+1) from parity (location exchange), for a total of (−1) as needed for antisymmetry.
  • Antisymmetric spin and antisymmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (−1) from spin exchange and (−1) from parity (location exchange), again for a total of (−1) as needed for antisymmetry.


In the first case the deuteron is a spin triplet, so that its total spin s is 1. It also has an even parity and therefore even orbital angular momentum l ; The lower its orbital angular momentum, the lower its energy. Therefore the lowest possible energy state has {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}}.

In the second case the deuteron is a spin singlet, so that its total spin s is 0. It also has an odd parity and therefore odd orbital angular momentum l. Therefore the lowest possible energy state has {{nowrap|s {{=}} 0}}, {{nowrap|l {{=}} 1}}.

Since {{nowrap|s {{=}} 1}} gives a stronger nuclear attraction, the deuterium ground state
Ground state
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state...

 is in the {{nowrap|s {{=}}1}}, {{nowrap|l {{=}} 0}} state.

The same considerations lead to the possible states of an isospin triplet having {{nowrap|s {{=}} 0}}, {{nowrap|l {{=}} even}} or {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} odd}}. Thus the state of lowest energy has {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 1}}, higher than that of the isospin singlet.

The analysis just given is in fact only approximate, both because isospin is not an exact symmetry, and more importantly because the strong nuclear interaction between the two nucleons is related to angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...

 in spin-orbit interaction
Spin-orbit interaction
In quantum physics, the spin-orbit interaction is any interaction of a particle's spin with its motion. The first and best known example of this is that spin-orbit interaction causes shifts in an electron's atomic energy levels due to electromagnetic interaction between the electron's spin and...

 that mixes different s and l states. That is, s and l are not constant in time (they do not commute
Commutativity
In mathematics an operation is commutative if changing the order of the operands does not change the end result. It is a fundamental property of many binary operations, and many mathematical proofs depend on it...

 with the Hamiltonian
Hamiltonian (quantum mechanics)
In quantum mechanics, the Hamiltonian H, also Ȟ or Ĥ, is the operator corresponding to the total energy of the system. Its spectrum is the set of possible outcomes when one measures the total energy of a system...

), and over time a state such as {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} may become a state of {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}}. Parity is still constant in time so these do not mix with odd l states (such as {{nowrap|s {{=}} 0}}, {{nowrap|l {{=}} 1}}). Therefore the quantum state of the deuterium is a superposition
Quantum superposition
Quantum superposition is a fundamental principle of quantum mechanics. It holds that a physical system exists in all its particular, theoretically possible states simultaneously; but, when measured, it gives a result corresponding to only one of the possible configurations.Mathematically, it...

 (a linear combination) of the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} state and the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}} state, even though the first component is much bigger. Since the total angular momentum j is also a good quantum number
Quantum number
Quantum numbers describe values of conserved quantities in the dynamics of the quantum system. Perhaps the most peculiar aspect of quantum mechanics is the quantization of observable quantities. This is distinguished from classical mechanics where the values can range continuously...

 (it is a constant in time), both components must have the same j, and therefore {{nowrap|j {{=}} 1}}. This is the total spin of the deuterium nucleus.

To summarize, the deuterium nucleus is antisymmetric in terms of isospin, and has spin 1 and even (+1) parity. The relative angular momentum of its nucleons l is not well defined, and the deuteron is a superposition of mostly {{nowrap|l {{=}} 0}} with some {{nowrap|l {{=}} 2}}.

Magnetic and electric multipoles


In order to find theoretically the deuterium magnetic dipole moment µ, one uses the formula for a nuclear magnetic moment
Nuclear magnetic moment
The nuclear magnetic moment is the magnetic moment of an atomic nucleus and arises from the spin of the protons and neutrons. It is mainly a magnetic dipole moment; the quadrupole moment does cause some small shifts in the hyperfine structure as well....


with
g(l) and g(s) are g-factors of the nucleons.

Since the proton and neutron have different values for g(l) and g(s), one must separate their contributions. Each gets half of the deuterium orbital angular momentum  and spin . One arrives at

where subscripts p and n stand for the proton and neutron, and {{nowrap|g(l)n {{=}} 0}}.

By using the same identities as here and using the value {{nowrap|g(l)p {{=}} {{val|1|ul=µN}}}}, we arrive at the following result, in nuclear magneton units

For the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} state ({{nowrap|j {{=}} 1}}), we obtain

For the {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}} state ({{nowrap|j {{=}} 1}}), we obtain

The measured value of the deuterium magnetic dipole moment, is {{val|0.857|u=µN}}. This suggests that the state of the deuterium is indeed only approximately {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 0}} state, and is actually a linear combination of (mostly) this state with {{nowrap|s {{=}} 1}}, {{nowrap|l {{=}} 2}} state.

The electric dipole is zero as usual
Shell model
In nuclear physics and nuclear chemistry, the nuclear shell model is a model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The first shell model was proposed by Dmitry Ivanenko in 1932...

.

The measured electric quadrupole
Quadrupole
A quadrupole or quadrapole is one of a sequence of configurations of—for example—electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure reflecting various orders of complexity.-Mathematical...

 of the deuterium is {{val|0.2859|u=e
Elementary charge
The elementary charge, usually denoted as e, is the electric charge carried by a single proton, or equivalently, the absolute value of the electric charge carried by a single electron. This elementary charge is a fundamental physical constant. To avoid confusion over its sign, e is sometimes called...

·fm2}}. While the order of magnitude is reasonable, since the deuterium radius is of order of 1 femtometer (see below) and its electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

 is e, the above model does not suffice for its computation. More specifically, the electric quadrupole does not get a contribution from the l =0 state (which is the dominant one) and does get a contribution from a term mixing the l =0 and the l =2 states, because the electric quadrupole operator does not commute with angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...

.
The latter contribution is dominant in the absence of a pure {{nowrap|l {{=}} 0}} contribution, but cannot be calculated without knowing the exact spatial form of the nucleons wavefunction
Wavefunction
Not to be confused with the related concept of the Wave equationA wave function or wavefunction is a probability amplitude in quantum mechanics describing the quantum state of a particle and how it behaves. Typically, its values are complex numbers and, for a single particle, it is a function of...

 inside the deuterium.

Higher magnetic and electric multipole moments cannot be calculated by the above model, for similar reasons.

Applications




Deuterium has a number of commercial and scientific uses. These include:

Nuclear reactors


Deuterium is useful in nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

 reactions, especially in combination with tritium
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...

, because of the large reaction rate (or nuclear cross section
Nuclear cross section
The nuclear cross section of a nucleus is used to characterize the probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction...

) and high energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 yield of the D–T reaction. There is an even higher-yield D–{{SimpleNuclide
Helium-3
Helium-3 is a light, non-radioactive isotope of helium with two protons and one neutron. It is rare on Earth, and is sought for use in nuclear fusion research...

 fusion reaction, though the breakeven
Breakeven
In economics & business, specifically cost accounting, the break-even point is the point at which cost or expenses and revenue are equal: there is no net loss or gain, and one has "broken even"...

 point of D–{{SimpleNuclide|Helium|3}} is higher than that of most other fusion reactions; together with the scarcity of {{SimpleNuclide|Helium|3}}, this makes it implausible as a practical power source until at least D–T and D–D fusion reactions have been performed on a commercial scale.

Deuterium is used in heavy water moderated fission reactors
Heavy water reactor
A pressurised heavy water reactor is a nuclear power reactor, commonly using unenriched natural uranium as its fuel, that uses heavy water as its coolant and moderator. The heavy water coolant is kept under pressure in order to raise its boiling point, allowing it to be heated to higher...

, usually as liquid D2O, to slow neutrons without high neutron absorption of ordinary hydrogen.

NMR spectroscopy


{{Main|Deuterium NMR}}
Deuterium NMR spectra are especially informative in the solid state because of its relatively small quadrupole moment in comparison with those of bigger quadrupolar nuclei such as chlorine-35, for example.

Tracing


In chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

, biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

 and environmental sciences, deuterium is used as a non-radioactive, stable isotopic
Stable isotope
Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...

 tracer, for example, in the doubly labeled water test. In chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

s and metabolic pathway
Metabolic pathway
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...

s, deuterium behaves somewhat similarly to ordinary hydrogen (with a few chemical differences, as noted). It can be distinguished from ordinary hydrogen most easily by its mass, using mass spectrometry
Mass spectrometry
Mass 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...

 or infrared spectrometry. Deuterium can be detected by femtosecond infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 spectroscopy, since the mass difference drastically affects the frequency of molecular vibrations; deuterium-carbon bond vibrations are found in locations free of other signals.

Measurements of small variations in the natural abundances of deuterium, along with those of the stable heavy oxygen isotopes 17O and 18O, are of importance in hydrology
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

, to trace the geographic origin of Earth's waters. The heavy isotopes of hydrogen and oxygen in rainwater (so-called meteoric water
Meteoric water
Meteoric water is a hydrologic term of long standing for water in the ground which originates from precipitation. This includes water from lakes, rivers, and icemelts, which all originate from precipitation indirectly.- Overview :...

) are enriched as a function of the environmental temperature of the region in which the precipitation falls (and thus enrichment is related to mean latitude). The relative enrichment of the heavy isotopes in rainwater (as referenced to mean ocean water), when plotted against temperature falls predictably along a line called the global meteoric water line
Global meteoric water line
The Global Meteoric Water Line is an equation defined by the geochemist Harmon Craigthat states the average relationship between hydrogen and oxygen isotope ratios in natural terrestrial waters, expressed as a worldwide average....

 (GMWL). This plot allows samples of precipitation-originated water to be identified along with general information about the climate in which it originated. Evaporative and other processes in bodies of water, and also ground water processes, also differentially alter the ratios of heavy hydrogen and oxygen isotopes in fresh and salt waters, in characteristic and often regionally-distinctive ways.

Contrast properties


Neutron scattering
Neutron scattering
Neutron scattering,the scattering of free neutrons by matter,is a physical processand an experimental technique using this processfor the investigation of materials.Neutron scattering as a physical process is of primordial importance...

 techniques particularly profit from availability of deuterated samples: The H and D cross sections are very distinct and different in sign, which allows contrast variation in such experiments. Further, a nuisance problem of ordinary hydrogen is its large incoherent neutron cross section, which is nil for D. The substitution of deuterium atoms for hydrogen atoms thus reduces scattering noise.

Hydrogen is an important and major component in all materials of organic chemistry and life science, but it barely interacts with X-rays. As hydrogen (and deuterium) interact strongly with neutrons, neutron scattering techniques, together with a modern deuteration facility, fills a niche in many studies of macromolecules in biology and many other areas.

Nuclear resonance spectroscopy


Deuterium is useful in hydrogen nuclear magnetic resonance spectroscopy (proton NMR
Proton NMR
Proton NMR is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the structure of its molecules. In samples where natural hydrogen is used, practically all of the hydrogen consists of the...

). NMR ordinarily requires compounds of interest to be analyzed as dissolved in solution. Because of deuterium's nuclear spin properties which differ from the light hydrogen usually present in organic molecules, NMR spectra of hydrogen/protium are highly differentiable from that of deuterium, and in practice deuterium is not "seen" by an NMR instrument tuned to light-hydrogen. Deuterated solvents (including heavy water, but also compounds like deuterated chloroform, CDCl3) are therefore routinely used in NMR spectroscopy, in order to allow only the light-hydrogen spectra of the compound of interest to be measured, without solvent-signal interference.

Suspicion of lighter element isotopes


The existence of nonradioactive isotopes of lighter elements had been suspected in studies of neon as early as 1913, and proven by mass spectrometry of light elements in 1920. The prevailing theory at the time, however, was that the isotopes were due to the existence of differing numbers of "nuclear electrons" in different atoms of an element. It was expected that hydrogen, with a measured average atomic mass very close to {{val|1|u=u}}, the known mass of the proton, always had a nucleus composed of a single proton (a known particle), and therefore could not contain any nuclear electrons without losing its charge entirely. Thus, hydrogen could have no heavy isotopes.

Deuterium predicted and finally detected



It was first detected spectroscopically in late 1931 by Harold Urey
Harold Urey
Harold Clayton Urey was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934...

, a chemist at Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...

. Urey's collaborator, Ferdinand Brickwedde
Ferdinand Brickwedde
Ferdinand Graft Brickwedde , a physicist at the National Bureau of Standards , in 1931 produced the first sample of hydrogen in which the spectrum of its heavy isotope, deuterium, could be observed...

, distilled
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

 five liter
Litér
- External links :*...

s of cryogenically produced
Cryogenics
In physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. A person who studies elements under extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of Celsius and Fahrenheit,...

 liquid hydrogen
Liquid hydrogen
Liquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be...

 to {{val|1|ul=mL}} of liquid, using the low-temperature physics laboratory that had recently been established at the National Bureau of Standards in Washington, D.C. (now the National Institute of Standards and Technology
National Institute of Standards and Technology
The National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory, otherwise known as a National Metrological Institute , which is a non-regulatory agency of the United States Department of Commerce...

). This concentrated the fraction of the mass-2 isotope of hydrogen to a degree that made its spectroscopic identification unambiguous.

Name


Urey called the new isotope "deuterium", from the Greek deuteros (second), and the nucleus to be called "deuteron" or "deuton". Isotopes and new elements were traditionally given the name that their discoverer decided, but some British chemists, like Ernest Rutherford
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson OM, FRS was a New Zealand-born British chemist and physicist who became known as the father of nuclear physics...

, wanted the isotope to be called "diplogen", from the Greek diploos (double), and the nucleus to be called diplon. The British magazine Nature also published a letter where only the denomination "diplogen" was used, perhaps annunciating that British could prefer that name over the name given by its discoverer. Urey and his two co-discoverers sent a letter to Nature saying that they had already considered that name and they had rejected it because "The compound NH1H2/2 would be called di-diplogen mono-hydrogen nitride", which would repeat the syllable "di." They also said that the British seemed to object on the basis that "neutron" and "deuton" could be confused with each other, and Urey pointed out that American workers were using the terms and they didn't seem to be having any such confusion.

Abundance, purification, and impact


The amount inferred for normal abundance of this heavy isotope of hydrogen was so small (only about 1 atom in 6400 hydrogen atoms in ocean water) that it had not noticeably affected previous measurements of (average) hydrogen atomic mass. This explained why it hadn't been experimentally suspected before. Urey was able to concentrate water to show partial enrichment of deuterium. Gilbert Newton Lewis prepared the first samples of pure heavy water in 1933.

The discovery of deuterium, coming before the discovery of the neutron
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...

 in 1932, was an experimental shock to theory, but when the neutron was reported, making deuterium's existence more explainable, deuterium won Urey the Nobel Prize
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...

 in chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...

 in 1934.

"Heavy water" experiments in World War II


{{Main|Heavy water}}
Shortly before the war, Hans von Halban
Hans von Halban
Hans von Halban was a French physicist, of Austrian-Jewish descent.- Family :He was descended on his father's side from Polish Jews, who left Kraków for Vienna in the 1850s...

 and Lew Kowarski
Lew Kowarski
Lew Kowarski was a naturalized French physicist, of Russian-Polish descent. He was a lesser known but important contributor to nuclear science.-Early life:...

 moved their research on neutron moderation from France to England, smuggling the entire global supply of heavy water (which had been made in Norway) across in twenty-six steel drums.

During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, Nazi Germany
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 was known to be conducting experiments using heavy water as moderator for a nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

 design. Such experiments were a source of concern because they might allow them to produce plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...

 for an atomic bomb. Ultimately it led to the Allied
Western Allies
The Western Allies were a political and geographic grouping among the Allied Powers of the Second World War. It generally includes the United Kingdom and British Commonwealth, the United States, France and various other European and Latin American countries, but excludes China, the Soviet Union,...

 operation called the "Norwegian heavy water sabotage
Norwegian heavy water sabotage
The Norwegian heavy water sabotage was a series of actions undertaken by Norwegian saboteurs during World War II to prevent the German nuclear energy project from acquiring heavy water , which could be used to produce nuclear weapons...

", the purpose of which was to destroy the Vemork
Vemork
Vemork is the name of a hydroelectric power plant outside Rjukan in Tinn, Norway. The plant was built by Norsk Hydro and opened in 1911, its main purpose being to fix nitrogen for the production of fertilizer. Vemork was later the site of the first plant in the world to mass-produce heavy water...

 deuterium production/enrichment facility in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

. At the time this was considered important to the potential progress of the war.

After World War II ended, the Allies discovered that Germany was not putting as much serious effort into the program as had been previously thought.{{Citation needed|date=March 2009}} The Germans had completed only a small, partly built experimental reactor (which had been hidden away). By the end of the war, the Germans did not even have a fifth of the amount of heavy water needed to run the reactor, partially due to the Norwegian heavy water sabotage operation.{{Citation needed|date=March 2009}} However, even had the Germans succeeded in getting a reactor operational (as the U.S. did with a graphite reactor in late 1942), they would still have been at least several years away from development of an atomic bomb with maximal effort. The engineering process, even with maximal effort and funding, required about two and a half years (from first critical reactor to bomb) in both the U.S. and U.S.S.R, for example.

Data

  • Density: {{val|0.180|u=kg/m3}} at STP
    Standard conditions for temperature and pressure
    Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...

     ({{val|0|u=degC}}, {{val|101.325|u=kPa}}).
  • Atomic weight: {{val|2.0141017926|u=u}}.
  • Mean abundance in ocean water (from VSMOW) 155.76 ±0.1 ppm (a ratio of 1 part per approximately 6420 parts), that is, about {{val|0.015|s=%}} of the atoms in a sample (by number, not weight)


Data at approximately {{val|18|u=K}} for D2 (triple point
Triple point
In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases of that substance coexist in thermodynamic equilibrium...

):
  • Density:
    • Liquid: {{val|162.4|u=kg/m3}}
    • Gas: {{val|0.452|u=kg/m3}}
  • Viscosity: {{val|12.6|u=µPa·s}} at {{val|300|u=K}} (gas phase)
  • Specific heat capacity at constant pressure cp:
    • Solid: {{val|2950|u=J/(kg·K)}}
    • Gas: {{val|5200|u=J/(kg·K)}}

Anti-deuterium


An antideuteron is the antiparticle of the nucleus of deuterium, consisting of an antiproton
Antiproton
The antiproton is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived since any collision with a proton will cause both particles to be annihilated in a burst of energy....

 and an antineutron
Antineutron
The antineutron is the antiparticle of the neutron with symbol . It differs from the neutron only in that some of its properties have equal magnitude but opposite sign. It has the same mass as the neutron, and no net electric charge, but has opposite baryon number...

. The antideuteron was first produced in 1965 at the Proton Synchrotron
Proton Synchrotron
The Proton Synchrotron is the first major particle accelerator at CERN, built as a 28 GeV proton accelerator in the late 1950s and put into operation in 1959. It takes the protons from the Proton Synchrotron Booster at a kinetic energy of 1.4 GeV and lead ions from the Low Energy Ion Ring at 72...

 at CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...

 and the Alternating Gradient Synchrotron at Brookhaven National Laboratory
Brookhaven National Laboratory
Brookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...

. A complete atom, with a positron
Positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...

 orbiting the nucleus, would be called antideuterium, but as of 2005 antideuterium has not yet been created. The proposed symbol for antideuterium is {{Element2|anti=yes|deuterium}}, that is, D with an overbar.

Pycnodeuterium


Deuterium atoms can be absorbed into a palladium (Pd) lattice. They are effectively solidified as an ultrahigh density deuterium lump (Pycnodeuterium) inside each octahedral space within the unit cell of the palladium host lattice. It was once reported that deuterium absorbed into palladium enabled nuclear cold fusion
Cold fusion
Cold fusion, also called low-energy nuclear reaction , refers to the hypothesis that nuclear fusion might explain the results of a group of experiments conducted at ordinary temperatures . Both the experimental results and the hypothesis are disputed...

. However, cold fusion by this mechanism has not been generally accepted by the scientific community.

Ultra-dense deuterium


The existence of ultra-dense deuterium is suggested by experiment. This material, at a density of {{val|140|u=kg/cm3}}, would be a million times more dense than regular deuterium, denser than the core of the Sun. This ultra-dense form of deuterium may facilitate achieving laser-induced fusion. Only minute amounts of ultra-dense deuterium have been produced thus far. At the moment, it is not known how the material is produced or if it remains stable without applied pressure, however, there is conjecture that it is possible to produce a new stable state of matter by compressing ultra-cold deuterium in a Rydberg
Rydberg matter
Rydberg matter is a phase of matter formed by Rydberg atoms; it was predicted around 1980 by É. A. Manykin, M. I. Ozhovan and P. P. Poluéktov. It has been formed from various elements like caesium, potassium, hydrogen and nitrogen; studies have been conducted on theoretical possibilities like...

 state.

See also

  • Isotopes of hydrogen
    Isotopes of hydrogen
    Hydrogen has three naturally occurring isotopes, sometimes denoted 1H, 2H, and 3H. Other, highly unstable nuclei have been synthesized in the laboratory but not observed in nature. The most stable radioisotope is tritium, with a half-life of 12.32 years...

  • Nuclear fusion
    Nuclear fusion
    Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

  • Tokamak
    Tokamak
    A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...

  • Tritium
    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...

  • Heavy water
    Heavy water
    Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...



{{Isotope|element=hydrogen
|lighter=hydrogen-1
Hydrogen atom
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively-charged proton and a single negatively-charged electron bound to the nucleus by the Coulomb force...


|heavier=hydrogen-3
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...


|before=See proton emission
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...


|after=Stable
}}

External links


{{Wiktionary}}
{{Use dmy dates|date=September 2010}}