Deuterium (hydrogen-2, symbol2H orD, also known asheavy hydrogen) is one of twostable isotopes ofhydrogen; the other is protium, or hydrogen-1,1H. The deuteriumnucleus (deuteron) contains oneproton and oneneutron, whereas the far more common1H has no neutrons.
The namedeuterium comes from Greekdeuteros, meaning "second".[3][4] American chemistHarold Urey discovered deuterium in 1931. Urey and others produced samples ofheavy water in which the2H had been highly concentrated. The discovery of deuterium won Urey aNobel Prize in 1934.
Thegas giant planets display the primordial ratio of deuterium. Comets show an elevated ratio similar to Earth's oceans (156 deuterium nuclei per 106 hydrogen nuclei). This reinforces theories that much of Earth's ocean water is of cometary origin.[5][6] The deuterium ratio of comet67P/Churyumov–Gerasimenko, as measured by theRosetta space probe, is about three times that of Earth water. This figure is the highest yet measured in a comet, thus deuterium ratios continue to be an active topic of research in both astronomy and climatology.[7]
Deuterium is often represented by thechemical symbol D. Since it is an isotope ofhydrogen withmass number 2, it is also represented by2H.IUPAC allows both D and2H, though2H is preferred.[8] A distinct chemical symbol is used for convenience because of the isotope's common use in various scientific processes. Also, its large mass difference withprotium (1H) confers non-negligible chemical differences with1H compounds. Deuterium has a mass of2.014102Da, about twice themean hydrogenatomic weight of1.007947 Da, or twice protium's mass of1.007825 Da. The isotope weight ratios within other elements are largely insignificant in this regard.
Inquantum mechanics, the energy levels of electrons in atoms depend on thereduced mass of the system of electron and nucleus. For ahydrogen atom, the role of reduced mass is most simply seen in theBohr model of the atom, where the reduced mass appears in a simple calculation of theRydberg constant and Rydberg equation, but the reduced mass also appears in theSchrödinger equation, and theDirac equation for calculating atomic energy levels.
The reduced mass of the system in these equations is close to the mass of a single electron, but differs from it by a small amount about equal to the ratio of mass of the electron to the nucleus. For1H, this amount is about1837/1836, or 1.000545, and for2H it is even smaller:3671/3670, or 1.0002725. The energies of electronic spectra lines for2H and1H therefore differ by the ratio of these two numbers, which is 1.000272. The wavelengths of all deuterium spectroscopic lines are shorter than the corresponding lines of light hydrogen, by 0.0272%. In astronomical observation, this corresponds to a blue Doppler shift of 0.0272% of thespeed of light, or 81.6 km/s.[9]
The differences are much more pronounced in vibrational spectroscopy such asinfrared spectroscopy andRaman spectroscopy,[10] and in rotational spectra such asmicrowave spectroscopy because thereduced mass of the deuterium is markedly higher than that of protium. Innuclear magnetic resonance spectroscopy, deuterium has a very differentNMR frequency (e.g. 61 MHz when protium is at 400 MHz) and is much less sensitive. Deuterated solvents are usually used in protium NMR to prevent the solvent from overlapping with the signal, thoughdeuterium NMR on its own right is also possible.
Deuterium is thought to have played an important role in setting the number and ratios of the elements that were formed in theBig Bang. Combiningthermodynamics and the changes brought about by cosmic expansion, one can calculate the fraction ofprotons andneutrons based on the temperature at the point that the universe cooled enough to allow formation ofnuclei. This calculation indicates seven protons for every neutron at the beginning ofnucleogenesis, a ratio that would remain stable even after nucleogenesis was over. This fraction was in favor of protons initially, primarily because the lower mass of the proton favored their production. As the Universe expanded, it cooled.Free neutrons and protons are less stable thanhelium nuclei, and the protons and neutrons had a strong energetic reason to formhelium-4. However, forming helium-4 requires the intermediate step of forming deuterium.
Through much of the few minutes after the Big Bang during which nucleosynthesis could have occurred, the temperature was high enough that the mean energy per particle was greater than the binding energy of weakly bound deuterium; therefore, any deuterium that was formed was immediately destroyed. This situation is known as thedeuterium bottleneck. The bottleneck delayed formation of any helium-4 until the Universe became cool enough to form deuterium (at about a temperature equivalent to 100 keV). At this point, there was a sudden burst of element formation (first deuterium, which immediately fused into helium). However, very soon thereafter, at twenty minutes after the Big Bang, the Universe became too cool for any furthernuclear fusion or nucleosynthesis. At this point, the elemental abundances were nearly fixed, with the only change as some of theradioactive products of Big Bang nucleosynthesis (such astritium) decay.[11] The deuterium bottleneck in the formation of helium, together with the lack of stable ways for helium to combine with hydrogen or with itself (no stable nucleus has a mass number of 5 or 8) meant that an insignificant amount of carbon, or any elements heavier than carbon, formed in the Big Bang. These elements thus required formation in stars. At the same time, the failure of much nucleogenesis during the Big Bang ensured that there would be plenty of hydrogen in the later universe available to form long-lived stars, such as the Sun.
Deuterium occurs in trace amounts naturally as deuteriumgas (2H2 or D2), but most deuterium atoms in theUniverse are bonded with1H to form a gas calledhydrogen deuteride (HD or1H2H).[12] Similarly, natural water contains deuterated molecules, almost all assemiheavy water HDO with only one deuterium.
The existence of deuterium on Earth, elsewhere in theSolar System (as confirmed by planetary probes), and in the spectra ofstars, is also an important datum incosmology. Gamma radiation from ordinary nuclear fusion dissociates deuterium into protons and neutrons, and there is no known natural process other thanBig Bang nucleosynthesis that might have produced deuterium at anything close to its observed natural abundance. Deuterium is produced by the rarecluster decay, and occasional absorption of naturally occurring neutrons by light hydrogen, but these are trivial sources. There is thought to be little deuterium in the interior of the Sun and other stars, as at these temperatures thenuclear fusion reactions that consume deuterium happen much faster than theproton–proton reaction that creates deuterium. However, deuterium persists in the outer solar atmosphere at roughly the same concentration as in Jupiter, and this has probably been unchanged since the origin of the Solar System. The natural abundance of2H seems to be a very similar fraction of hydrogen, wherever hydrogen is found, unless there are obvious processes at work that concentrate it.
The existence of deuterium at a low but constant primordial fraction in all hydrogen is another one of the arguments in favor of theBig Bang over theSteady State theory of the Universe. The observed ratios of hydrogen to helium to deuterium in the universe are difficult to explain except with a Big Bang model. It is estimated that the abundances of deuterium have not evolved significantly since their production about 13.8 billion years ago.[13] Measurements ofMilky Way galactic deuterium from ultraviolet spectral analysis show a ratio of as much as 23 atoms of deuterium per million hydrogen atoms in undisturbed gas clouds, which is only 15% below theWMAP estimated primordial ratio of about 27 atoms per million from the Big Bang. This has been interpreted to mean that less deuterium has been destroyed in star formation in the Milky Way galaxy than expected, or perhaps deuterium has been replenished by a large in-fall of primordial hydrogen from outside the galaxy.[14] In space a few hundred light years from the Sun, deuterium abundance is only 15 atoms per million, but this value is presumably influenced by differential adsorption of deuterium onto carbon dust grains in interstellar space.[15]
The abundance of deuterium inJupiter's atmosphere has been directly measured by theGalileo space probe as 26 atoms per million hydrogen atoms. ISO-SWS observations find 22 atoms per million hydrogen atoms in Jupiter.[16] and this abundance is thought to represent close to the primordial Solar System ratio.[6] This is about 17% of the terrestrial ratio of 156 deuterium atoms per million hydrogen atoms.
Comets such asComet Hale-Bopp andHalley's Comet have been measured to contain more deuterium (about 200 atoms 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 per million hydrogen in Comet103P/Hartley (a formerKuiper belt object), a ratio almost exactly that in Earth's oceans (155.76 ± 0.1, but in fact from 153 to 156 ppm), emphasizes the theory that Earth's surface water may be largely from comets.[5][6] Most recently the2H1HR of67P/Churyumov–Gerasimenko as measured byRosetta is about three times that of Earth water.[7] This has caused renewed interest in suggestions that Earth's water may be partly of asteroidal origin.
Deuterium has also been observed to be concentrated over the mean solar abundance in other terrestrial planets, in particular Mars and Venus.[17]
Deuterium is produced for industrial, scientific and military purposes, by starting with ordinary water—a small fraction of which is naturally occurringheavy water—and then separating out the heavy water by theGirdler sulfide process, distillation, or other methods.[18]
In theory, deuterium for heavy water could be created in a nuclear reactor, but separation from ordinary water is the cheapest bulk production process.
Another major producer of heavy water is India. All but one of India's atomic energy plants are pressurized heavy water plants, which use natural (i.e., not enriched) uranium. India has eight heavy water plants, of which seven are in operation. Six plants, of which five are in operation, are based on D–H exchange in ammonia gas. The other two plants extract deuterium from natural water in a process that useshydrogen sulfide gas at high pressure.
While India is self-sufficient in heavy water for its own use, India also exports reactor-grade heavy water.
Mean abundance in ocean water (fromVSMOW) 155.76 ± 0.1 atoms of deuterium per million atoms of all isotopes of hydrogen (about 1 atom of in 6420); that is, about 0.015% of all atoms of hydrogen (any isotope)
Compared to hydrogen in its natural composition on Earth, pure deuterium (2H2) has a highermelting point (18.72 K vs. 13.99 K), a higherboiling point (23.64 vs. 20.27 K), a highercritical temperature (38.3 vs. 32.94 K) and a higher critical pressure (1.6496 vs. 1.2858 MPa).[19]
The physical properties of deuterium compounds can exhibit significantkinetic isotope effects and other physical and chemical property differences from the protium analogs.2H2O, for example, is moreviscous than normalH2O.[20] There are differences in bond energy and length for compounds of heavy hydrogen isotopes compared to protium, which are larger than the isotopic differences in any other element. Bonds involving deuterium andtritium are somewhat stronger than the corresponding bonds in protium, and these differences are enough to cause significant changes in biological reactions. Pharmaceutical firms are interested in the fact that2H is harder to remove from carbon than1H.[21]
Deuterium can replace1H in water molecules to form heavy water (2H2O), which is about 10.6% denser than normal water (so that ice made from it sinks in normal water). Heavy water is slightly toxic ineukaryotic 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 develop slowly.[22] Despite this toxicity, consumption of heavy water under normal circumstances does not pose ahealth threat to humans. It is estimated that a 70 kg (154 lb) person might drink 4.8 litres (1.3 US gal) of heavy water without serious consequences.[23] 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 deuteron hasspin +1 ("triplet state") and is thus aboson. TheNMR frequency of deuterium is significantly different from normal 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, versus light hydrogen. The two stable isotopes of hydrogen can also be distinguished by usingmass spectrometry.
The triplet deuteron nucleon is barely bound atEB =2.23 MeV, and none of the higher energy states are bound. The singlet deuteron is a virtual state, with a negative binding energy of~60 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.[24]
Deuterium is one of only five stablenuclides with an odd number of protons and an odd number of neutrons. (2H,6Li,10B,14N,180mTa; the long-lived radionuclides40K,50V,138La,176Lu also occur naturally.) Mostodd–odd nuclei are unstable tobeta decay, because the decay products areeven–even, and thus more strongly bound, due tonuclear 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 thePauli exclusion principle which would require one or the other identical particle with the same spin to have some other different quantum number, such asorbital angular momentum. But orbital angular momentum of either particle gives a lowerbinding energy for the system, mainly due to increasing distance of the particles in the steep gradient of the nuclear force. In both cases, this causes thediproton anddineutron to beunstable.
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, anucleon. While only the proton has electric charge, this is often negligible due to the weakness of theelectromagnetic interaction relative to thestrong nuclear interaction. The symmetry relating the proton and neutron is known asisospin and denotedI (or sometimesT).
Isospin is anSU(2) symmetry, like ordinaryspin, so is completely analogous to it. The proton and neutron, each of which have isospin-1/2, form an isospin doublet (analogous to aspin doublet), with a "down" state (↓) being a neutron and an "up" state (↑) being a proton.[citation needed] A pair of nucleons can either be in an antisymmetric state of isospin calledsinglet, or in a symmetric state calledtriplet. In terms of the "down" state and "up" state, the singlet is
, which can also be written :
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 highlyexcited state of it), a nucleus with two protons, and a nucleus with two neutrons. These states are not stable.
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 underparity (i.e. has an "even" or "positive" parity), and antisymmetric if the deuteron is antisymmetric under parity (i.e. has 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 spins is 1. It also has an even parity and therefore even orbital angular momentuml. The lower its orbital angular momentum, the lower its energy. Therefore, the lowest possible energy state hass = 1,l = 0.
In the second case the deuteron is a spin singlet, so that its total spins is 0. It also has an odd parity and therefore odd orbital angular momentuml. Therefore, the lowest possible energy state hass = 0,l = 1.
Sinces = 1 gives a stronger nuclear attraction, the deuteriumground state is in thes = 1,l = 0 state.
The same considerations lead to the possible states of an isospin triplet havings = 0,l = even ors = 1,l = odd. Thus, the state of lowest energy hass = 1,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 thestrong nuclear interaction between the two nucleons is related toangular momentum inspin–orbit interaction that mixes differents andl states. That is,s andl are not constant in time (they do notcommute with theHamiltonian), and over time a state such ass = 1,l = 0 may become a state ofs = 1,l = 2. Parity is still constant in time, so these do not mix with oddl states (such ass = 0,l = 1). Therefore, thequantum state of the deuterium is asuperposition (a linear combination) of thes = 1,l = 0 state and thes = 1,l = 2 state, even though the first component is much bigger. Since thetotal angular momentumj is also a goodquantum number (it is a constant in time), both components must have the samej, and thereforej = 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 nucleonsl is not well defined, and the deuteron is a superposition of mostlyl = 0 with somel = 2.
Since the proton and neutron have different values forg(l) andg(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, andg(l)n = 0.
By using the same identities ashere and using the valueg(l)p = 1, one gets the following result, in units of thenuclear magnetonμN
For thes = 1,l = 0 state (j = 1), we obtain
For thes = 1,l = 2 state (j = 1), we obtain
The measured value of the deuteriummagnetic dipole moment, is0.857 μN, which is 97.5% of the0.879 μN value obtained by simply adding moments of the proton and neutron. This suggests that the state of the deuterium is indeed to a good approximations = 1,l = 0 state, which occurs with both nucleons spinning in the same direction, but their magnetic moments subtracting because of the neutron's negative moment.
But the slightly lower experimental number than that which results from simple addition of proton and (negative) neutron moments shows that deuterium is actually a linear combination of mostlys = 1,l = 0 state with a slight admixture ofs = 1,l = 2 state.
The measured electricquadrupole of the deuterium is0.2859 e·fm2. While the order of magnitude is reasonable, since the deuteron radius is of order of 1 femtometer (see below) and itselectric charge is e, the above model does not suffice for its computation. More specifically, theelectric quadrupole does not get a contribution from thel = 0 state (which is the dominant one) and does get a contribution from a term mixing thel = 0 and thel = 2 states, because the electric quadrupoleoperator does notcommute withangular momentum.
The latter contribution is dominant in the absence of a purel = 0 contribution, but cannot be calculated without knowing the exact spatial form of the nucleonswavefunction inside the deuterium.
Higher magnetic and electricmultipole moments cannot be calculated by the above model, for similar reasons.
Ionized deuterium in afusor reactor giving off its characteristic pinkish-red glow
Deuterium is used inheavy water moderated fission reactors, usually as liquid2H2O, to slow neutrons without the high neutron absorption of ordinary hydrogen.[30] This is a common commercial use for larger amounts of deuterium.
Experimentally, deuterium is the most commonnuclide used infusion reactor designs, especially in combination withtritium, because of the large reaction rate (ornuclear cross section) and highenergy yield of the deuterium–tritium (DT) reaction. There is an even higher-yield2H–3He fusion reaction, though thebreakeven point of2H–3He is higher than that of most other fusion reactions; together with the scarcity of3He, this makes it implausible as a practical power source, at least until DT and deuterium–deuterium (DD) fusion have been performed on a commercial scale. Commercial nuclear fusion is not yet an accomplished technology.
Deuterium is most commonly used in hydrogennuclear magnetic resonance spectroscopy (proton NMR) in the following way. 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 for1H. Deuterated solvents (including heavy water, but also compounds like deuteratedchloroform, CDCl3 or C2HCl3, 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.
Nuclear magnetic resonance spectroscopy can also be used to obtain information about the deuteron's environment in isotopically labelled samples (deuterium NMR). For example, the configuration of hydrocarbon chains in lipid bilayers can be quantified using solid state deuterium NMR with deuterium-labelled lipid molecules.[31]
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.
Measurements of small variations in the natural abundances of deuterium, along with those of the stable heavyoxygen isotopes17O and18O, are of importance inhydrology, to trace the geographic origin of Earth's waters. The heavy isotopes of hydrogen and oxygen in rainwater (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 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 theglobal 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.[34] The ratio of concentration of2H to1H is usually indicated with a delta asδ2H and the geographic patterns of these values are plotted in maps termed as isoscapes. Stable isotopes are incorporated into plants and animals and an analysis of the ratios in a migrant bird or insect can help suggest a rough guide to their origins.[35][36]
Neutron scattering techniques particularly profit from availability of deuterated samples: The1H and2H cross sections are very distinct and different in sign, which allows contrast variation in such experiments. Further, a nuisance problem of normal hydrogen is its large incoherent neutron cross section, which is nil for2H. The substitution of deuterium for normal hydrogen 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 atoms (including deuterium) interact strongly with neutrons; neutron scattering techniques, together with a modern deuteration facility,[37] fills a niche in many studies of macromolecules in biology and many other areas.
See below. Most stars, including the Sun, generate energy over most of their lives by fusing hydrogen into heavier elements; yet such fusion of light hydrogen (protium) has never been successful in the conditions attainable on Earth. Thus, all artificial fusion, including the hydrogen fusion in hydrogen bombs, requires heavy hydrogen (deuterium, tritium, or both).[38]
A deuterated drug is asmall molecule medicinal product in which one or more of thehydrogen atoms in the drug molecule have been replaced by deuterium. Because of thekinetic isotope effect, deuterium-containing drugs may have significantly lower rates ofmetabolism, and hence a longerhalf-life.[39][40][41] In 2017,deutetrabenazine became the first deuterated drug to receive FDA approval.[42]
Deuterium has been shown to lengthen the period of oscillation of the circadian clock when dosed in rats, hamsters, andGonyaulax dinoflagellates.[48][49][50][51] In rats, chronic intake of 25%2H2O disrupts circadian rhythm by lengthening the circadian period ofsuprachiasmatic nucleus-dependent rhythms in the brain's hypothalamus.[50] Experiments in hamsters also support the theory that deuterium acts directly on the suprachiasmatic nucleus to lengthen the free-running circadian period.[52]
The existence of nonradioactive isotopes of lighter elements had been suspected in studies of neon as early as 1913,[citation needed] and proven by mass spectrometry of light elements in 1920.[citation needed] At that time the neutron had not yet been discovered, and the prevailing theory was that isotopes of an element differ by the existence of additionalprotons in the nucleus accompanied by an equal number ofnuclear electrons. In this theory, the deuterium nucleus with mass two and charge one would contain two protons and one nuclear electron. However, it was expected that the element hydrogen with a measured average atomic mass very close to1 Da, the known mass of the proton, always has a nucleus composed of a single proton (a known particle), and could not contain a second proton. Thus, hydrogen was thought to have no heavy isotopes.[citation needed]
It was first detected spectroscopically in late 1931 byHarold Urey, a chemist atColumbia University. Urey's collaborator,Ferdinand Brickwedde,distilled fiveliters ofcryogenically producedliquid hydrogen to1 mL of liquid, using the low-temperature physics laboratory that had recently been established at the National Bureau of Standards (nowNational Institute of Standards and Technology) in Washington, DC. The technique had previously been used to isolate heavy isotopes of neon. The cryogenic boiloff technique concentrated the fraction of the mass-2 isotope of hydrogen to a degree that made its spectroscopic identification unambiguous.[53][54]
Urey created the namesprotium,deuterium, andtritium in an article published in 1934. The name is based in part on advice fromGilbert N. Lewis who had proposed the name "deutium". The name comes from Greekdeuteros 'second', and the nucleus was to be called a "deuteron" or "deuton". Isotopes and new elements were traditionally given the name that their discoverer decided. Some British scientists, such asErnest Rutherford, wanted to call the isotope "diplogen", from Greekdiploos 'double', and the nucleus to be called "diplon".[4][55]
The amount inferred for normal abundance of deuterium was so small (only about 1 atom in 6400 hydrogen atoms in seawater [156 parts per million]) that it had not noticeably affected previous measurements of (average) hydrogen atomic mass. This explained why it hadn't been suspected before. Urey was able to concentrate water to show partial enrichment of deuterium.Lewis, Urey's graduate advisor atBerkeley, had prepared and characterized the first samples of pure heavy water in 1933. The discovery of deuterium, coming before the discovery of theneutron in 1932, was an experimental shock totheory; but when the neutron was reported, making deuterium's existence more explicable, Urey was awarded theNobel Prize in Chemistry only three years after the isotope's isolation. Lewis was deeply disappointed by theNobel Committee's decision in 1934 and several high-ranking administrators at Berkeley believed this disappointment played a central role inhis suicide a decade later.[56][57][58][4]
Shortly before the war,Hans von Halban andLew Kowarski moved their research on neutron moderation from France to Britain, smuggling the entire global supply of heavy water (which had been made in Norway) across in twenty-six steel drums.[59][60]
DuringWorld War II,Nazi Germany was known to be conducting experiments using heavy water as moderator for anuclear reactor design. Such experiments were a source of concern because they might allow them to produceplutonium for anatomic bomb. Ultimately it led to theAllied operation called the "Norwegian heavy water sabotage", the purpose of which was to destroy theVemork deuterium production/enrichment facility in Norway. 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. The Germans had completed only a small, partly built experimental reactor (which had been hidden away) and had been unable to sustain a chain reaction. 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,[clarification needed] partially due to the Norwegian heavy water sabotage operation. However, even if the Germans had succeeded in getting a reactor operational (as the U.S. did withChicago Pile-1 in late 1942), they would still have been at least several years away from the development of anatomic bomb. 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. andU.S.S.R., for example.
The "Sausage" device casing of theIvy MikeH bomb, attached to instrumentation and cryogenic equipment. The 20-ft-tall bomb held a cryogenicDewar flask with room for 160 kg of liquid deuterium.
The 62-tonIvy Mike device built by the United States and exploded on 1 November 1952, was the first fully successfulhydrogen bomb (thermonuclear bomb). In this context, it was the first bomb in which most of the energy released came fromnuclear reaction stages that followed the primarynuclear fission stage of theatomic bomb. The Ivy Mike bomb was a factory-like building, rather than a deliverable weapon. At its center, a very large cylindrical, insulatedvacuum flask orcryostat, heldcryogenic liquid deuterium in a volume of about 1000liters (160 kilograms in mass, if this volume had been completely filled). Then, a conventional atomic bomb (the "primary") at one end of the bomb was used to create the conditions of extreme temperature and pressure that were needed to set off thethermonuclear reaction.
Within a few years, so-called "dry" hydrogen bombs were developed that did not need cryogenic hydrogen. Released information suggests that allthermonuclear weapons built since then containchemical compounds of deuterium and lithium in their secondary stages. The material that contains the deuterium is mostlylithium deuteride, with the lithium consisting of the isotopelithium-6. When the lithium-6 is bombarded with fastneutrons from the atomic bomb,tritium (hydrogen-3) is produced, and then the deuterium and the tritium quickly engage inthermonuclear fusion, releasing abundant energy,helium-4, and even more free neutrons. "Pure" fusion weapons such as theTsar Bomba are believed to be obsolete. In most modern ("boosted") thermonuclear weapons, fusion directly provides only a small fraction of the total energy. Fission of a naturaluranium-238 tamper by fast neutrons produced from D–T fusion accounts for a much larger (i.e. boosted) energy release than the fusion reaction itself.
In August 2018, scientists announced the transformation of gaseous deuterium into aliquid metallic form. This may help researchers better understandgas giant planets, such as Jupiter, Saturn and someexoplanets, since such planets are thought to contain a lot of liquid metallic hydrogen, which may be responsible for their observed powerfulmagnetic fields.[61][62]
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