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75-432: The HiPEP thruster differs from earlier ion thrusters because the xenon ions are produced using a combination of microwave and magnetic fields. The ionization is achieved through a process called Electron Cyclotron Resonance (ECR). In ECR, the small number of free electrons present in the neutral gas gyrate around the static magnetic field lines. The injected microwaves' frequency is set to match this gyrofrequency and

150-464: A Xe nucleus has a spin of 1/2, and therefore a zero electric quadrupole moment , the Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms, and the hyperpolarization persists for long periods even after the engendering light and vapor have been removed. Spin polarization of Xe can persist from several seconds for xenon atoms dissolved in blood to several hours in

225-695: A barium salt of a krypton oxoacid . Ar Kr and Kr H polyatomic ions have been investigated and there is evidence for Kr Xe or KrXe . The reaction of KrF 2 with B(OTeF 5 ) 3 produces an unstable compound, Kr(OTeF 5 ) 2 , that contains a krypton- oxygen bond. A krypton- nitrogen bond is found in the cation [HC≡N–Kr–F] , produced by the reaction of KrF 2 with [HC≡NH] [AsF 6 ] below −50 °C. HKrCN and HKrC≡CH (krypton hydride-cyanide and hydrokryptoacetylene) were reported to be stable up to 40 K . Krypton hydride (Kr(H 2 ) 4 ) crystals can be grown at pressures above 5 GPa. They have

300-492: A propellant for ion thrusters in spacecraft. Naturally occurring xenon consists of seven stable isotopes and two long-lived radioactive isotopes. More than 40 unstable xenon isotopes undergo radioactive decay , and the isotope ratios of xenon are an important tool for studying the early history of the Solar System . Radioactive xenon-135 is produced by beta decay from iodine-135 (a product of nuclear fission ), and

375-447: A band of emission lines that span the visual spectrum, but the most intense lines occur in the region of blue light, producing the coloration. Xenon is a trace gas in Earth's atmosphere , occurring at a volume fraction of 87 ± 1 nL/L ( parts per billion ), or approximately 1 part per 11.5 million. It is also found as a component of gases emitted from some mineral springs . Given

450-409: A bright greenish-blue light. Krypton is mixed with argon in energy efficient fluorescent lamps, reducing the power consumption, but also reducing the light output and raising the cost. Krypton costs about 100 times as much as argon. Krypton (along with xenon) is also used to fill incandescent lamps to reduce filament evaporation and allow higher operating temperatures . Krypton's white discharge

525-448: A double-column plant, the liquid oxygen produced will contain small quantities of krypton and xenon. By additional fractional distillation, the liquid oxygen may be enriched to contain 0.1–0.2% of a krypton/xenon mixture, which is extracted either by adsorption onto silica gel or by distillation. Finally, the krypton/xenon mixture may be separated into krypton and xenon by further distillation. Worldwide production of xenon in 1998

600-407: A face-centered cubic structure where krypton octahedra are surrounded by randomly oriented hydrogen molecules. Earth has retained all of the noble gases that were present at its formation except helium . Krypton's concentration in the atmosphere is about 1  ppm . It can be extracted from liquid air by fractional distillation . The amount of krypton in space is uncertain, because measurement

675-477: A few chemical reactions such as the formation of xenon hexafluoroplatinate , the first noble gas compound to be synthesized. Xenon is used in flash lamps and arc lamps , and as a general anesthetic . The first excimer laser design used a xenon dimer molecule (Xe 2 ) as the lasing medium , and the earliest laser designs used xenon flash lamps as pumps . Xenon is also used to search for hypothetical weakly interacting massive particles and as

750-438: A large number of xenon compounds have been discovered and described. Almost all known xenon compounds contain the electronegative atoms fluorine or oxygen. The chemistry of xenon in each oxidation state is analogous to that of the neighboring element iodine in the immediately lower oxidation state. Three fluorides are known: XeF 2 , XeF 4 , and XeF 6 . XeF is theorized to be unstable. These are

825-464: A less electronegative element include F–Xe–N(SO 2 F) 2 and F–Xe–BF 2 . The latter is synthesized from dioxygenyl tetrafluoroborate, O 2 BF 4 , at −100 °C. Krypton Krypton (from Ancient Greek : κρυπτός , romanized :  kryptos 'the hidden one') is a chemical element ; it has symbol Kr and atomic number 36. It is a colorless, odorless noble gas that occurs in trace amounts in

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900-474: A liquid, xenon has a density of up to 3.100 g/mL, with the density maximum occurring at the triple point. Liquid xenon has a high polarizability due to its large atomic volume, and thus is an excellent solvent. It can dissolve hydrocarbons, biological molecules, and even water. Under the same conditions, the density of solid xenon, 3.640 g/cm , is greater than the average density of granite , 2.75 g/cm . Under gigapascals of pressure , xenon forms

975-407: A metallic phase. Solid xenon changes from Face-centered cubic (fcc) to hexagonal close packed (hcp) crystal phase under pressure and begins to turn metallic at about 140 GPa, with no noticeable volume change in the hcp phase. It is completely metallic at 155 GPa. When metallized, xenon appears sky blue because it absorbs red light and transmits other visible frequencies. Such behavior

1050-471: A metastable, but highly repulsive ground state . The ground state complex quickly dissociates into unbound atoms: The result is an exciplex laser which radiates energy at 248 nm, near the ultraviolet portion of the spectrum , corresponding with the energy difference between the ground state and the excited state of the complex. Compounds with krypton bonded to atoms other than fluorine have also been discovered. There are also unverified reports of

1125-441: A mistaken identification. Under extreme conditions, krypton reacts with fluorine to form KrF 2 according to the following equation: Krypton gas in a krypton fluoride laser absorbs energy from a source, causing the krypton to react with fluorine gas, producing the exciplex krypton fluoride, a temporary complex in an excited energy state: The complex can undergo spontaneous or stimulated emission, reducing its energy state to

1200-504: A pale-yellow solid. It explodes above −35.9 °C into xenon and oxygen gas, but is otherwise stable. A number of xenon oxyfluorides are known, including XeOF 2 , XeOF 4 , XeO 2 F 2 , and XeO 3 F 2 . XeOF 2 is formed by reacting OF 2 with xenon gas at low temperatures. It may also be obtained by partial hydrolysis of XeF 4 . It disproportionates at −20 °C into XeF 2 and XeO 2 F 2 . XeOF 4

1275-459: A plasma in low density gases. Previously the electrons required were provided by a hollow cathode . The thruster itself is in the 20-50 kW class, with a specific impulse of 6,000-9,000 seconds, and a propellant throughput capability exceeding 100 kg/kW. The goal of the project, as of June 2003, was to achieve a technology readiness level of 4-5 within 2 years. The pre-prototype HiPEP produced 670  milli newton (mN) of thrust at

1350-452: A power level of 39.3 kW using 7.0 mg/s of fuel giving a specific impulse of 9620 s. Downrated to 24.4 kW, the HiPEP used 5.6 mg/s of fuel giving a specific impulse of 8270 s and 460 mN of thrust. Phase 1 of HiPEP development concluded in early 2003. Conceptual Design of the thruster was completed, and individual component testing concluded. A full-scale laboratory thruster

1425-588: A real compound. Theoretical calculations indicate that the linear molecule XeCl 2 is less stable than the van der Waals complex. Xenon tetrachloride and xenon dibromide are even more unstable and they cannot be synthesized by chemical reactions. They were created by radioactive decay of ICl 4 and IBr 2 , respectively. Three oxides of xenon are known: xenon trioxide ( XeO 3 ) and xenon tetroxide ( XeO 4 ), both of which are dangerously explosive and powerful oxidizing agents, and xenon dioxide (XeO 2 ), which

1500-411: A resonance is established. Energy is transferred from the right-hand polarized portion of the microwave to the electrons. This energy is then transferred to the bulk gas/ plasma via the rare - yet important - collisions between electrons and neutrals. During these collisions, electrons can be knocked free from the neutrals, forming ion-electron pairs. The process is a highly efficient means of creating

1575-474: A substrate of chilled crystal of nickel to spell out the three-letter company initialism. It was the first-time atoms had been precisely positioned on a flat surface. Xenon has atomic number 54; that is, its nucleus contains 54 protons . At standard temperature and pressure , pure xenon gas has a density of 5.894 kg/m , about 4.5 times the density of the Earth's atmosphere at sea level, 1.217 kg/m . As

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1650-494: A total mass of the atmosphere of 5.15 × 10 kilograms (1.135 × 10  lb), the atmosphere contains on the order of 2.03 gigatonnes (2.00 × 10 long tons; 2.24 × 10 short tons) of xenon in total when taking the average molar mass of the atmosphere as 28.96 g/mol which is equivalent to some 394-mass ppb. Xenon is obtained commercially as a by-product of the separation of air into oxygen and nitrogen . After this separation, generally performed by fractional distillation in

1725-491: A useful laser medium . From 1960 to 1983, the official definition of the metre was based on the wavelength of one spectral line of krypton-86, because of the high power and relative ease of operation of krypton discharge tubes . Krypton was discovered in Britain in 1898 by William Ramsay , a Scottish chemist, and Morris Travers , an English chemist, in residue left from evaporating nearly all components of liquid air . Neon

1800-431: Is a medium lived fission product and thus escapes from spent fuel when the cladding is removed. Krypton is used occasionally as an insulating gas between window panes. SpaceX Starlink uses krypton as a propellant for their electric propulsion system . Krypton is considered to be a non-toxic asphyxiant . Being lipophilic , krypton has a significant anaesthetic effect (although the mechanism of this phenomenon

1875-447: Is a member of the zero- valence elements that are called noble or inert gases . It is inert to most common chemical reactions (such as combustion, for example) because the outer valence shell contains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound. In a gas-filled tube , xenon emits a blue or lavenderish glow when excited by electrical discharge . Xenon emits

1950-504: Is about 3% fission products) than it does in air. However, there is as of 2022 no commercial effort to extract xenon from spent fuel during nuclear reprocessing . Naturally occurring xenon is composed of seven stable isotopes : Xe, Xe, and Xe. The isotopes Xe and Xe are predicted by theory to undergo double beta decay , but this has never been observed so they are considered stable. In addition, more than 40 unstable isotopes have been studied. The longest-lived of these isotopes are

2025-415: Is characterized by several sharp emission lines ( spectral signatures ) the strongest being green and yellow. Krypton is one of the products of uranium fission . Solid krypton is white and has a face-centered cubic crystal structure , which is a common property of all noble gases (except helium , which has a hexagonal close-packed crystal structure). Naturally occurring krypton in Earth's atmosphere

2100-425: Is composed of five stable isotopes , plus one isotope ( Kr) with such a long half-life (9.2×10  years) that it can be considered stable. (This isotope has the third-longest known half-life among all isotopes for which decay has been observed; it undergoes double electron capture to Se ). In addition, about thirty unstable isotopes and isomers are known. Traces of Kr, a cosmogenic nuclide produced by

2175-446: Is derived from meteoric activity and solar winds. The first measurements suggest an abundance of krypton in space. Krypton's multiple emission lines make ionized krypton gas discharges appear whitish, which in turn makes krypton-based bulbs useful in photography as a white light source. Krypton is used in some photographic flashes for high speed photography . Krypton gas is also combined with mercury to make luminous signs that glow with

2250-455: Is formed by the partial hydrolysis of XeF 6 ... ...or the reaction of XeF 6 with sodium perxenate, Na 4 XeO 6 . The latter reaction also produces a small amount of XeO 3 F 2 . XeO 2 F 2 is also formed by partial hydrolysis of XeF 6 . XeOF 4 reacts with CsF to form the XeOF 5 anion, while XeOF 3 reacts with

2325-404: Is generated by passing brief electric current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method. In 1939, American physician Albert R. Behnke Jr. began exploring the causes of "drunkenness" in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, and discovered that this caused

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2400-401: Is not produced directly but as a product of successive beta decays and thus it cannot absorb any neutrons in a nuclear explosion which occurs in fractions of a second. The stable isotope xenon-132 has a fission product yield of over 4% in the thermal neutron fission of U which means that stable or nearly stable xenon isotopes have a higher mass fraction in spent nuclear fuel (which

2475-505: Is released during the reprocessing of fuel rods from nuclear reactors. Concentrations at the North Pole are 30% higher than at the South Pole due to convective mixing. Like the other noble gases, krypton is chemically highly unreactive. The rather restricted chemistry of krypton in the +2 oxidation state parallels that of the neighboring element bromine in the +1 oxidation state; due to

2550-404: Is sometimes used as an artistic effect in gas discharge "neon" tubes. Krypton produces much higher light power than neon in the red spectral line region, and for this reason, red lasers for high-power laser light-shows are often krypton lasers with mirrors that select the red spectral line for laser amplification and emission, rather than the more familiar helium-neon variety, which could not achieve

2625-522: Is the most significant (and unwanted) neutron absorber in nuclear reactors . Xenon was discovered in England by the Scottish chemist William Ramsay and English chemist Morris Travers on July 12, 1898, shortly after their discovery of the elements krypton and neon . They found xenon in the residue left over from evaporating components of liquid air . Ramsay suggested the name xenon for this gas from

2700-417: Is unusual for a metal and is explained by the relatively small width of the electron bands in that state. Liquid or solid xenon nanoparticles can be formed at room temperature by implanting Xe ions into a solid matrix. Many solids have lattice constants smaller than solid Xe. This results in compression of the implanted Xe to pressures that may be sufficient for its liquefaction or solidification. Xenon

2775-506: Is weakly acidic, dissolving in alkali to form unstable xenate salts containing the HXeO 4 anion. These unstable salts easily disproportionate into xenon gas and perxenate salts, containing the XeO 6 anion. Barium perxenate, when treated with concentrated sulfuric acid , yields gaseous xenon tetroxide: To prevent decomposition, the xenon tetroxide thus formed is quickly cooled into

2850-490: The Chernobyl nuclear accident . Stable or extremely long lived isotopes of xenon are also produced in appreciable quantities in nuclear fission. Xenon-136 is produced when xenon-135 undergoes neutron capture before it can decay. The ratio of xenon-136 to xenon-135 (or its decay products) can give hints as to the power history of a given reactor and the absence of xenon-136 is a "fingerprint" for nuclear explosions, as xenon-135

2925-474: The Greek word ξένον xénon , neuter singular form of ξένος xénos , meaning 'foreign(er)', 'strange(r)', or 'guest'. In 1902, Ramsay estimated the proportion of xenon in the Earth's atmosphere to be one part in 20 million. During the 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography . This led him to the invention of the xenon flash lamp in which light

3000-426: The atmosphere and is often used with other rare gases in fluorescent lamps . Krypton is chemically inert . Krypton, like the other noble gases, is used in lighting and photography . Krypton light has many spectral lines , and krypton plasma is useful in bright, high-powered gas lasers (krypton ion and excimer lasers), each of which resonates and amplifies a single spectral line. Krypton fluoride also makes

3075-482: The cosmic ray irradiation of Kr, also occur in nature: this isotope is radioactive with a half-life of 230,000 years. Krypton is highly volatile and does not stay in solution in near-surface water, but Kr has been used for dating old (50,000–800,000 years) groundwater . Kr is an inert radioactive noble gas with a half-life of 10.76 years. It is produced by the fission of uranium and plutonium , such as in nuclear bomb testing and nuclear reactors . Kr

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3150-432: The gas phase and several days in deeply frozen solid xenon. In contrast, Xe has a nuclear spin value of 3 ⁄ 2 and a nonzero quadrupole moment , and has t 1 relaxation times in the millisecond and second ranges. Some radioactive isotopes of xenon (for example, Xe and Xe) are produced by neutron irradiation of fissionable material within nuclear reactors . Xe is of considerable significance in

3225-563: The isotope krypton-86. This agreement replaced the 1889 international prototype meter , which was a metal bar located in Sèvres . This also made obsolete the 1927 definition of the ångström based on the red cadmium spectral line, replacing it with 1 Å = 10  m. The krypton-86 definition lasted until the October 1983 conference, which redefined the meter as the distance that light travels in vacuum during 1/299,792,458 s. Krypton

3300-399: The outgassing of xenon into the atmosphere. Unlike the lower-mass noble gases, the normal stellar nucleosynthesis process inside a star does not form xenon. Nucleosynthesis consumes energy to produce nuclides more massive than iron-56 , and thus the synthesis of xenon represents no energy gain for a star. Instead, xenon is formed during supernova explosions during the r-process , by

3375-429: The primordial Xe, which undergoes double electron capture with a half-life of 1.8 × 10  yr , and Xe, which undergoes double beta decay with a half-life of 2.11 × 10 yr . Xe is produced by beta decay of I , which has a half-life of 16 million years. Xe, Xe, Xe, and Xe are some of the fission products of U and Pu , and are used to detect and monitor nuclear explosions. Nuclei of two of

3450-411: The scandide contraction it is difficult to oxidize the 4p elements to their group oxidation states. Until the 1960s no noble gas compounds had been synthesized. Following the first successful synthesis of xenon compounds in 1962, synthesis of krypton difluoride ( KrF 2 ) was reported in 1963. In the same year, KrF 4 was reported by Grosse, et al. , but was subsequently shown to be

3525-420: The alkali metal fluorides KF , RbF and CsF to form the XeOF 4 anion. Xenon can be directly bonded to a less electronegative element than fluorine or oxygen, particularly carbon . Electron-withdrawing groups, such as groups with fluorine substitution, are necessary to stabilize these compounds. Numerous such compounds have been characterized, including: Other compounds containing xenon bonded to

3600-514: The atmosphere of planet Jupiter is unusually high, about 2.6 times that of the Sun. This abundance remains unexplained, but may have been caused by an early and rapid buildup of planetesimals —small, sub-planetary bodies—before the heating of the presolar disk ; otherwise, xenon would not have been trapped in the planetesimal ices. The problem of the low terrestrial xenon may be explained by covalent bonding of xenon to oxygen within quartz , reducing

3675-582: The calorimeter of the NA48 experiment at CERN containing about 27 tonnes of liquid krypton. This usage is rare, since liquid argon is less expensive. The advantage of krypton is a smaller Molière radius of 4.7 cm, which provides excellent spatial resolution with little overlapping. The other parameters relevant for calorimetry are: radiation length of X 0 =4.7 cm, and density of 2.4 g/cm . Krypton-83 has application in magnetic resonance imaging (MRI) for imaging airways. In particular, it enables

3750-678: The design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel ). Xe reactor poisoning was a major factor in the Chernobyl disaster . A shutdown or decrease of power of a reactor can result in buildup of Xe, with reactor operation going into a condition known as the iodine pit . Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may emanate from cracked fuel rods , or fissioning of uranium in cooling water . Isotope ratios of xenon produced in natural nuclear fission reactors at Oklo in Gabon reveal

3825-513: The divers to perceive a change in depth. From his results, he deduced that xenon gas could serve as an anesthetic . Although Russian toxicologist Nikolay V. Lazarev apparently studied xenon anesthesia in 1941, the first published report confirming xenon anesthesia was in 1946 by American medical researcher John H. Lawrence, who experimented on mice. Xenon was first used as a surgical anesthetic in 1951 by American anesthesiologist Stuart C. Cullen, who successfully used it with two patients. Xenon and

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3900-419: The form of an overabundance of xenon-129. He inferred that this was a decay product of radioactive iodine-129 . This isotope is produced slowly by cosmic ray spallation and nuclear fission , but is produced in quantity only in supernova explosions. Because the half-life of I is comparatively short on a cosmological time scale (16 million years), this demonstrated that only a short time had passed between

3975-505: The much more plentiful argon, which makes up over 1% by volume of earth's atmosphere, costs less than a cent per liter. Within the Solar System, the nucleon fraction of xenon is 1.56 × 10 , for an abundance of approximately one part in 630 thousand of the total mass. Xenon is relatively rare in the Sun 's atmosphere, on Earth , and in asteroids and comets . The abundance of xenon in

4050-421: The noble gases argon , krypton , and radon , including argon fluorohydride (HArF), krypton difluoride (KrF 2 ), and radon fluoride . By 1971, more than 80 xenon compounds were known. In November 1989, IBM scientists demonstrated a technology capable of manipulating individual atoms . The program, called IBM in atoms , used a scanning tunneling microscope to arrange 35 individual xenon atoms on

4125-481: The operation of nuclear fission reactors . Xe has a huge cross section for thermal neutrons , 2.6×10   barns , and operates as a neutron absorber or " poison " that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production. However, the designers had made provisions in

4200-533: The other noble gases were for a long time considered to be completely chemically inert and not able to form compounds . However, while teaching at the University of British Columbia , Neil Bartlett discovered that the gas platinum hexafluoride (PtF 6 ) was a powerful oxidizing agent that could oxidize oxygen gas (O 2 ) to form dioxygenyl hexafluoroplatinate ( O 2 [PtF 6 ] ). Since O 2 (1165 kJ/mol) and xenon (1170 kJ/mol) have almost

4275-553: The presence of NaF yields high-purity XeF 4 . The xenon fluorides behave as both fluoride acceptors and fluoride donors, forming salts that contain such cations as XeF and Xe 2 F 3 , and anions such as XeF 5 , XeF 7 , and XeF 8 . The green, paramagnetic Xe 2 is formed by the reduction of XeF 2 by xenon gas. XeF 2 also forms coordination complexes with transition metal ions. More than 30 such complexes have been synthesized and characterized. Whereas

4350-402: The radiologist to distinguish between hydrophobic and hydrophilic surfaces containing an airway. Although xenon has potential for use in computed tomography (CT) to assess regional ventilation, its anesthetic properties limit its fraction in the breathing gas to 35%. A breathing mixture of 30% xenon and 30% krypton is comparable in effectiveness for CT to a 40% xenon fraction, while avoiding

4425-507: The reactor properties during chain reaction that took place about 2 billion years ago. Because xenon is a tracer for two parent isotopes, xenon isotope ratios in meteorites are a powerful tool for studying the formation of the Solar System . The iodine–xenon method of dating gives the time elapsed between nucleosynthesis and the condensation of a solid object from the solar nebula . In 1960, physicist John H. Reynolds discovered that certain meteorites contained an isotopic anomaly in

4500-412: The result may indicate that Mars lost most of its primordial atmosphere, possibly within the first 100 million years after the planet was formed. In another example, excess Xe found in carbon dioxide well gases from New Mexico is believed to be from the decay of mantle -derived gases from soon after Earth's formation. After Neil Bartlett's discovery in 1962 that xenon can form chemical compounds,

4575-492: The same first ionization potential , Bartlett realized that platinum hexafluoride might also be able to oxidize xenon. On March 23, 1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate . Bartlett thought its composition to be Xe [PtF 6 ] , but later work revealed that it was probably a mixture of various xenon-containing salts. Since then, many other xenon compounds have been discovered, in addition to some compounds of

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4650-401: The same multi-watt outputs. The krypton fluoride laser is important in nuclear fusion energy research in confinement experiments. The laser has high beam uniformity, short wavelength , and the spot size can be varied to track an imploding pellet. In experimental particle physics , liquid krypton is used to construct quasi-homogeneous electromagnetic calorimeters . A notable example is

4725-428: The same rate it is produced during steady operation of a nuclear reactor. However, if power is reduced or the reactor is scrammed , less xenon is destroyed than is produced from the beta decay of its parent nuclides . This phenomenon called xenon poisoning can cause significant problems in restarting a reactor after a scram or increasing power after it had been reduced and it was one of several contributing factors in

4800-429: The slow neutron-capture process ( s-process ) in red giant stars that have exhausted their core hydrogen and entered the asymptotic giant branch , and from radioactive decay, for example by beta decay of extinct iodine-129 and spontaneous fission of thorium , uranium , and plutonium . Xenon-135 is a notable neutron poison with a high fission product yield . As it is relatively short lived, it decays at

4875-420: The solar gas cloud. In a similar way, xenon isotopic ratios such as Xe/ Xe and Xe/ Xe are a powerful tool for understanding planetary differentiation and early outgassing. For example, the atmosphere of Mars shows a xenon abundance similar to that of Earth (0.08 parts per million ) but Mars shows a greater abundance of Xe than the Earth or the Sun. Since this isotope is generated by radioactive decay,

4950-441: The stable isotopes of xenon , Xe and Xe (both stable isotopes with odd mass numbers), have non-zero intrinsic angular momenta ( nuclear spins , suitable for nuclear magnetic resonance ). The nuclear spins can be aligned beyond ordinary polarization levels by means of circularly polarized light and rubidium vapor. The resulting spin polarization of xenon nuclei can surpass 50% of its maximum possible value, greatly exceeding

5025-416: The starting points for the synthesis of almost all xenon compounds. The solid, crystalline difluoride XeF 2 is formed when a mixture of fluorine and xenon gases is exposed to ultraviolet light. The ultraviolet component of ordinary daylight is sufficient. Long-term heating of XeF 2 at high temperatures under an NiF 2 catalyst yields XeF 6 . Pyrolysis of XeF 6 in

5100-423: The supernova and the time the meteorites had solidified and trapped the I. These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the Solar System , because the I isotope was likely generated shortly before the Solar System was formed, seeding the solar gas cloud with isotopes from a second source. This supernova source may also have caused collapse of

5175-406: The thermal equilibrium value dictated by paramagnetic statistics (typically 0.001% of the maximum value at room temperature , even in the strongest magnets ). Such non-equilibrium alignment of spins is a temporary condition, and is called hyperpolarization . The process of hyperpolarizing the xenon is called optical pumping (although the process is different from pumping a laser ). Because

5250-534: The unwanted effects of a high partial pressure of xenon gas. The metastable isotope krypton-81m is used in nuclear medicine for lung ventilation/perfusion scans , where it is inhaled and imaged with a gamma camera . Krypton-85 in the atmosphere has been used to detect clandestine nuclear fuel reprocessing facilities in North Korea and Pakistan . Those facilities were detected in the early 2000s and were believed to be producing weapons-grade plutonium. Krypton-85

5325-449: The xenon fluorides are well characterized, the other halides are not. Xenon dichloride , formed by the high-frequency irradiation of a mixture of xenon, fluorine, and silicon or carbon tetrachloride , is reported to be an endothermic, colorless, crystalline compound that decomposes into the elements at 80 °C. However, XeCl 2 may be merely a van der Waals molecule of weakly bound Xe atoms and Cl 2 molecules and not

5400-544: Was constructed for Phase 2 of the HiPEP's development. However, with cancellation of the Jupiter Icy Moon Orbiter mission in 2005, HiPEP's development also came to a halt. Before cancellation, HiPEP completed a 2000 hour wear test. Xenon Xenon is a chemical element ; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo

5475-539: Was discovered by a similar procedure by the same workers just a few weeks later. William Ramsay was awarded the 1904 Nobel Prize in Chemistry for discovery of a series of noble gases , including krypton. In 1960, the International Bureau of Weights and Measures defined the meter as 1,650,763.73 wavelengths of light emitted in the vacuum corresponding to the transition between the 2p 10 and 5d 5 levels in

5550-565: Was estimated at 5,000–7,000 cubic metres (180,000–250,000 cu ft). At a density of 5.894 grams per litre (0.0002129 lb/cu in) this is equivalent to roughly 30 to 40 tonnes (30 to 39 long tons; 33 to 44 short tons). Because of its scarcity, xenon is much more expensive than the lighter noble gases—approximate prices for the purchase of small quantities in Europe in 1999 were 10  € /L (=~€1.7/g) for xenon, 1 €/L (=~€0.27/g) for krypton, and 0.20 €/L (=~€0.22/g) for neon, while

5625-398: Was reported in 2011 with a coordination number of four. XeO 2 forms when xenon tetrafluoride is poured over ice. Its crystal structure may allow it to replace silicon in silicate minerals. The XeOO cation has been identified by infrared spectroscopy in solid argon . Xenon does not react with oxygen directly; the trioxide is formed by the hydrolysis of XeF 6 : XeO 3

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