Deuterium
Encyclopedia : D : DE : DEU : Deuterium
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| General | |
| Name, symbol | deuterium, H or D |
| Neutrons | 1 |
| Protons | 1 |
| Nuclide Data | |
| Natural abundance | 0.015% |
| Half-life | stable |
| Isotope mass | u |
| Spin | 1+ |
| Excess energy | 13135.720 ± 0.001 keV |
| Binding energy | 2224.573 ± 0.002 keV |
The chemical symbol 2H identifies deuterium. The unofficial symbol D is also often used, even though deuterium is not a chemical element in its own right.
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.
The deuteron has spin +1 and is thus a boson. The NMR frequency of deuterium is significantly different from common light hydrogen. The two stable isotopes of hydrogen can be distinguished physically 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.
Applications
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.
Deuterium is particlarly 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 specroscopy, 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 [link].
Deuterium, as large quantities of salted, but otherwise very pure, heavy water, is essential to the operation of the Sudbury Neutrino Observatory. See the section in heavy water on this, and also the Wiki SNO.
History
The existence of nonradioactive isotopes of lighter elements had been suspected in studies of neon as early as 1913, and proven by mass spectroscopy in 1920. The prevailing theory at the time, however, was that the isotopes were due to the existence of differing numbers of "nuclear electrons" and 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.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 5 liters of cryogenically-produced liquid hydrogen to 1 milliliter of liquid and showed spectroscopically that it contained a very small amount of isotope of hydrogen with an atomic mass of 2, and 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 measurments 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 (see heavy water). 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.
For the history of heavy water production, see that topic. During World War II, Nazi Germany was known to be conducting experiments using heavy water as moderator for a nuclear reactor design. This was a source of concern because it might allow them to produce plutonium for an atomic bomb. Ultimately, it led to a seemingly important Allied operation, the Norwegian heavy water sabotage, to destroy the Vemork deuterium production/enrichment facility in Norway. It turned out, however, that Germany was not putting any serious efforts into the program, and only had a small partly-built experimental reactor hidden away. At 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 America 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 2 and a half years, from first critical reactor to bomb, in both the U.S. and U.S.S.R).
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.
- density:
- *solid: 195 kg/m3
- *gas: 0.452 kg/m3
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 and the [Alternating Gradient Synchrotron] at Brookhaven National Laboratory. 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.
Appearances in
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.
References
- [Nuclear Data Evaluation Lab]
- [Annotated bibliography for Deuterium from the Alsos Digital Library for Nuclear Issues]
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All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.