Deuterium

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Hydrogen-2
Full table
General
Name, symbol	deuterium, ²H or D
Neutrons	1
Protons	1
Nuclide Data
Natural abundance	0.015%
Half-life	stable
Isotope mass	2.01355321270 u
Spin	1+
Excess energy	13135.720 ± 0.001 keV
Binding energy	2224.573 ± 0.002 keV

Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of planet Earth of approximately one atom in 6500 of hydrogen (~154 PPM). Deuterium thus accounts for approximately 0.015% (on a weight basis 0.030%) of all naturally occurring hydrogen (see VSMOW; the abundance changes slightly from one kind of natural water to another). The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen nucleus consists only of a proton and no neutrons. The isotope name is formed from the Greek deuteros meaning "two", to denote the two subatomic particles comprising the nucleus.

1 Chemical symbol, occurrence, and properties
2 Applications
3 History
4 Data
5 Anti-deuterium
6 Appearances in pop culture
7 See also
8 References

[edit] Chemical symbol, occurrence, and properties

As an isotope of hydrogen, the accepted chemical symbol for deuterium is ²H. Despite this, the unofficial chemical element-like symbol - D - has been adopted by many. The significant difference in relative atomic weight compared with pure protium (^{1^{H) may well be the reason for this; Deuterium's atomic weight is 2.014 amu, compared to the mean hydrogen weight of 1.007947 amu, and protium's of 1.007825 amu. The isotope weight ratios within other chemical elements are largely insignificant in this regard, explaining the lack of unique isotope symbols elsewhere.}}

Deuterium occurs in trace amounts naturally as deuterium gas, written ²H₂ or D₂, but most natural occurrence in the universe is bonded with a typical ¹H atom, a gas called hydrogen deuteride (HD or ¹H²H).<ref>IUPAC Commission on Nomenclature of Inorganic Chemistry (2001). "Names for Muonium and Hydrogen Atoms and their Ions". Pure and Applied Chemistry 73: 377–380.</ref>

The deuteron has spin +1 and is thus a boson. The NMR frequency of deuterium is significantly different from common light hydrogen. Infrared spectroscopy 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, verses light hydrogen. The two stable isotopes of hydrogen can also be distinguished by using mass spectrometry.

The physical properties of deuterium compounds can be different from the hydrogen analogs; for example, D₂O is more viscous than H₂O.

Deuterium behaves chemically 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 are somewhat stronger than the corresponding bonds in light hydrogen, and these differences are enough to make significant changes in biological reactions (see heavy water).

Deuterium can replace the normal hydrogen in water molecules to form heavy water (D₂O), which is about 10.6% more dense than normal water (enough that ice made from it, sinks in ordinary water). Heavy water is modestly 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 would not pose a health threat to humans unless very large quantities (in excess of 10 liters) were consumed over many days. 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.

The existence of deuterium on Earth, elsewhere in the solar system (as confirmed by planetary probes), and in the spectra of stars, is an important datum in cosmology. Stellar fusion destroys deuterium, and there are no known natural processes (for example, see the rare cluster decay), other than the Big Bang nucleosynthesis, which might have produced deuterium at anything close to the observed natural abundance of deuterium. This abundance seems to be a very similar fraction of hydrogen, wherever hydrogen is found. Thus, the existence of deuterium is one of the arguments in favour of the Big Bang theory over the steady state theory of the universe.

The world's leading "producer" of deuterium (technically, merely enricher or concentrator of deuterium) is Canada, in the form of heavy water. Canada uses heavy water as a neutron moderator for the operation of the CANDU reactor design.

[edit] Applications

Image:Deuterium lamp 1.png

Deuterium is useful in nuclear fusion reactions, especially in combination with tritium, because of the large reaction rate (or cross section) and high energy yield of the D-T reaction, and in the even higher-yield D-He₃ fusion reaction, though the breakeven is higher than with most other fusion reactions, making it implausible as a practical power source until at least D-T and D-D fusion reactions have been performed. Unlike protium, deuterium undergoes fusion purely via the strong interaction, making its use for commercial power plausible.

In chemistry and biochemistry, deuterium is used as a non-radioactive isotopic tracer in molecules to study chemical reactions and metabolic pathways, because chemically it behaves similarly to ordinary hydrogen, but it can be distinguished from ordinary hydrogen by its mass, using mass spectrometry or infrared spectrometry.

Neutron scattering 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 and delivers much clearer signals in deuterated samples. Hydrogen occurs in all materials of organic chemistry and life science, but cannot be seen by X-ray diffraction methods. Hydrogen can be seen by neutron diffraction and scattering, which makes neutron scattering, together with a modern deuteration facility, indispensable for many studies of macromolecules in biology and many other areas.

Deuterium is useful in hydrogen nuclear magnetic resonance (1H-NMR) spectroscopy. 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.

Deuterium can also be used for femtosecond infrared 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, to trace the geographic origin of Earth's waters. The heavy isotopes of hydrogen and oxygen in rainwater (so-called meteoric water) 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 (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 [1].

The proton and neutron making up deuterium can be dissociated through neutral current interactions with neutrinos. The cross section for this interaction is comparatively large, and deuterium was successfully used as a neutrino target in the Sudbury Neutrino Observatory experiment.

[edit] History

[edit] Lighter element isotopes suspected

The existence of nonradioactive isotopes of lighter elements had been suspected in studies of neon as early as 1913, and proven by mass spectroscopy 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 1 u, and a nucleus thought to be composed of a single proton (a known particle), could not contain nuclear electrons, and thus could have no heavy isotopes.

[edit] Deuterium "predicted" and finally detected

Deuterium was "predicted" in 1926 by Walter Russell, using his "spiral" periodic table, and first detected in late 1931 by Harold Urey, a chemist at Columbia University. Urey distilled five liters of cryogenically-produced liquid hydrogen to 1 mL of liquid and showed spectroscopically that it contained a very small amount of an isotope of hydrogen with an atomic mass of 2; Urey called the isotope "deuterium" from the Greek and Latin words for "two." The amount inferred for normal abundance of this heavy isotope 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. Urey was also 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 in 1932, was an experimental shock to theory, and after the neutron was reported, deuterium won Urey the Nobel Prize in chemistry in 1934.

[edit] "Heavy water" experiments in World War II

During World War II, Nazi Germany was known to be conducting experiments using heavy water as moderator for a nuclear reactor design. (Heavy water is water in which the hydrogen is deuterium.) Such experiments were a source of concern because they might allow them to produce plutonium for an atomic bomb. Ultimately, it led to (what seemed to be important at that time) the Allied operation called the "Norwegian heavy water sabotage," the purpose of which was to destroy the Vemork deuterium production/enrichment facility in Norway.

After World War II ended, the Allies discovered that Germany was not putting as much serious effort into the program as has had been previously thought. 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 the amount of heavy water needed to run the reactor, partially due to the Norwegian heavy water sabotage operation. 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 (see the article heavy water for a more complete history of its production and use).

[edit] Data

density: 0.180 kg/m³ at STP (0 °C, 101.325 kPa).
atomic weight: 2.01355321270.
mean abundance in ocean water (see VSMOW) about 0.0156 % of H atoms = 1/6400 H atoms.

Data at approximately 18 K for D₂ (triple point):

density:

solid: 195 kg/m³
gas: 0.452 kg/m³

viscosity: 1.3 µPa·s
specific heat capacity at constant pressure c_p:

solid: 2950 J/(kg·K)
gas: 5200 J/(kg·K)

[edit] Anti-deuterium

An antideuteron is the antiparticle of the nucleus of deuterium, consisting of an antiproton and an antineutron. The antideuteron was first produced in 1965 at the Proton Synchrotron at CERN<ref>Massam, T., et al. (1965). "Experimental observation of antideuteron production.". Il Nuovo Cimento 39: 10–14.</ref> and the Alternating Gradient Synchrotron at Brookhaven National Laboratory<ref>Dorfan, D. E., et al. (Jun 1965). "Observation of Antideuterons". Phys. Rev. Lett. 14 (24): 1003-1006. DOI:10.1103/PhysRevLett.14.1003.</ref>. A complete atom, with a positron orbiting the nucleus, would be called antideuterium, but as of 2005 antideuterium has not yet been created. The symbol for antideuterium is the same as for deuterium, except with a bar over it.

[edit] Appearances in pop culture

The reactions of matter and antimatter (more specifically, deuterium and anti-deuterium) are the basis for warp travel in the Star Trek universe, with deuterium and anti-deuterium being used as a fuel of sorts.

In the Star Trek episode The City on the Edge of Forever Earth's time-line had been altered by a member of the Enterprise crew, and the German Nazis were "able to complete their heavy water experiments" and win World War II. Captain Kirk and Mr. Spock go back in time to attempt to repair and restore Earth's original time-line.