Xenon

Xenon (PronEng|ˈzɛnɒn [Xenon, entry in the Oxford English Dictionary, prepared by J. A. Simpson and E. S. C. Weiner, vol. 20, second edition, Oxford: Clarendon Press, 1989. ISBN 0-19-861232-X (vol. 20), ISBN 0-19-861186-2 (set.)] or IPAlink-en|ˈziːnɒn [ [http://dictionary.reference.com/browse/xenon xenon] , entry in Dictionary.com Unabridged (v 1.1), accessed on line February 19, 2007. Transcribed into IPA.] ) is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the earth's atmosphere in trace amounts. [cite web
author=Staff | year=2007
url=http://www.infoplease.com/ce6/sci/A0852881.html
title=Xenon | work=Columbia Electronic Encyclopedia
edition=6th edition | publisher=Columbia University Press
accessdate=2007-10-23 ] Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.cite web
author=Husted, Robert; Boorman, Mollie | date=December 15, 2003
url=http://periodic.lanl.gov/elements/54.html | title=Xenon
publisher=Los Alamos National Laboratory, Chemical Division
accessdate=2007-09-26] [cite book
last=Rabinovich | first=Viktor Abramovich
coauthors=Vasserman, A. A.; Nedostup, V. I.; Veksler, L. S.
year=1988
title=Thermophysical properties of neon, argon, krypton, and xenon
edition=English-language edition
publisher=Hemisphere Publishing Corp.
location=Washington, DC | id=ISBN 0195218337
url=http://adsabs.harvard.edu/abs/1988wdch...10.....R —National Standard Reference Data Service of the USSR. Volume 10.]

Naturally occurring xenon consists of nine stable isotopes. There are also over 40 unstable isotopes that undergo radioactive decay. The isotope ratios of xenon are an important tool for studying the early history of the Solar System. Xenon-135 is produced as a result of nuclear fission and acts as a neutron absorber in nuclear reactors.

Xenon is used in flash lamps and arc lamps, and as a general anesthetic.cite journal
author=Sanders, Robert D.; Ma, Daqing; Maze, Mervyn
title=Xenon: elemental anaesthesia in clinical practice
journal=British Medical Bulletin
year=2005 | volume=71 | issue=1 | pages=115–135
doi= 10.1093/bmb/ldh034
accessdate=2007-10-02
pmid=15728132 ] The first excimer laser design used a xenon dimer molecule (Xe₂) as its lasing medium, and the earliest laser designs used xenon flash lamps as pumps. Xenon is also being used to search for hypothetical weakly interacting massive particles and as the propellant for ion thrusters in spacecraft.

History

Xenon was discovered in England by William Ramsay and Morris Travers on July 12, 1898, shortly after their discovery of the elements krypton and neon. They found it in the residue left over from evaporating components of liquid air. [cite journal
author=W. Ramsay and M. W. Travers
title=On the extraction from air of the companions of argon, and neon
journal=Report of the Meeting of the British Association for the Advancement of Science
year=1898 | pages=828 ] [cite web | url=http://education.jlab.org/itselemental/ele054.html
title=It's Elemental - Xenon | accessdate=2007-06-16
last=Gagnon | first=Steve
publisher=Thomas Jefferson National Accelerator Facility ] Ramsay suggested the name "xenon" for this gas from the Greek word "ξένον" [xenon] , neuter singular form of "ξένος" [xenos] , meaning 'foreign(er)', 'strange(r)', or 'guest'. [cite book
author=Anonymous
editor=Daniel Coit Gilman, Harry Thurston Peck, Frank Moore Colby
year=1904 | title=The New International Encyclopædia
publisher=Dodd, Mead and Company | pages=p. 906] [cite book
author=Staff | year=1991
title=The Merriam-Webster New Book of Word Histories
pages=p. 513 | publisher=Merriam-Webster, Inc.
id=ISBN 0877796033 ] In 1902, Ramsay estimated the proportion of xenon in the Earth's atmosphere as one part in 20 million. [cite journal
last=Ramsay | first=William
title=An Attempt to Estimate the Relative Amounts of Krypton and of Xenon in Atmospheric Air
journal=Proceedings of the Royal Society of London
year=1902 | volume=71 | pages=421–426
url=http://adsabs.harvard.edu/abs/1902RSPS...71..421R
accessdate=2007-10-02
doi=10.1098/rspl.1902.0121 ]

[
Xenon flash] During the 1930s, 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 is generated by sending a brief electrical current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method. [cite web
author=Anonymous | title=History
url=http://www.millisecond-cine.com/history.html
publisher=Millisecond Cinematography
accessdate=2007-11-07] [cite web
last=Paschotta | first=Rüdiger
date=November 1, 2007
url=http://www.rp-photonics.com/lamp_pumped_lasers.html
title=Lamp-pumped lasers
work=Encyclopedia of Laser Physics and Technology
publisher=RP Photonics | accessdate=2007-11-07 ]

In 1939 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 the divers to perceive a change in depth. From his results, he deduced that xenon gas could serve as an anesthetic. Although Lazharev, in Russia, apparently studied xenon anesthesia in 1941, the first published report confirming xenon anesthesia was in 1946 by J. H. Lawrence, who experimented on mice. Xenon was first used as a surgical anesthetic in 1951 by Stuart C. Cullen, who successfully operated on two patients. [cite journal
author=Marx, Thomas; Schmidt, Michael; Schirmer, Uwe; Reinelt, Helmut
title=Xenon anesthesia
journal=Journal of the Royal Society of Medicine
year=2000 | volume=93 | pages=513–517
url=http://www.jrsm.org/cgi/reprint/93/10/513.pdf
accessdate=2007-10-02 |format=PDF]

In 1960 physicist John H. Reynolds discovered that certain meteorites contained an isotopic anomaly in 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. As the half-life of ¹²⁹I is comparatively short on a cosmological time scale, only 16 million years, this demonstrated that only a short time had passed between the supernova and the time the meteorites had solidified and trapped the ¹²⁹I. These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the Solar System, as the ¹²⁹I isotope was likely generated before the Solar System was formed, but not long before, and seeded the solar gas cloud isotopes with isotopes from a second source. This supernova source may also have caused collapse of the solar gas cloud. [cite book
first=Donald D. | last=Clayton | year=1983
title=Principles of Stellar Evolution and Nucleosynthesis
pages=p. 75 | edition=2nd edition
publisher=University of Chicago Press | id=ISBN 0226109534 ] [cite web
author=Bolt, B. A.; Packard, R. E.; Price, P. B. | year=2007
url=http://content.cdlib.org/xtf/view?docId=hb1r29n709&doc.view=content&chunk.id=div00061&toc.depth=1&brand=oac&anchor.id=0
title=John H. Reynolds, Physics: Berkeley
publisher=The University of California, Berkeley
accessdate=2007-10-01 ]

Xenon and 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 (PtF₆) was a powerful oxidizing agent that could oxidize oxygen gas (O₂) to form dioxygenyl hexafluoroplatinate (O₂⁺ [PtF₆] ⁻). [cite journal
title=Dioxygenyl hexafluoroplatinate (V), O₂⁺ [PtF₆] ⁻
author=Neil Bartlett and D. H. Lohmann
journal = Proceedings of the Chemical Society
volume =
publisher = Chemical Society
location = London
issue = 3
pages = 115
month = March
year = 1962
url =
doi = 10.1039/PS9620000097 ] Since O₂ and xenon have almost 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.cite journal
title = Xenon hexafluoroplatinate (V) Xe⁺ [PtF₆] ⁻
author = Bartlett, N.
journal = Proceedings of the Chemical Society
volume =
publisher = Chemical Society
location = London
issue = 6
pages = 218
month = June
year = 1962
url =
doi = 10.1039/PS9620000197] cite web
url=http://www.chem.umn.edu/class/2301/barany03f/fun/beautiful1.pdf
title=Chemistry at its Most Beautiful
accessdate=2007-09-13 |last=Freemantel |first=Michael
date=August 25, 2003 |publisher=Chemical & Engineering News|format=PDF] Bartlett thought its composition to be Xe⁺ [PtF₆] ⁻, although later work has revealed that it was probably a mixture of various xenon-containing salts.cite journal
last = Graham | first = L.
coauthors = Graudejus, O., Jha N.K., and Bartlett, N.
year = 2000
title = Concerning the nature of XePtF₆
journal = Coordination Chemistry Reviews | volume = 197
pages = 321–334 | doi = 10.1016/S0010-8545(99)00190-3 ] [p. 392, §11.4, "Inorganic Chemistry", translated by Mary Eagleson and William Brewer, edited by Bernhard J. Aylett, San Diego: Academic Press, 2001, ISBN 0-12-352651-5; translation of "Lehrbuch der Anorganischen Chemie", originally founded by A. F. Holleman, continued by Egon Wiberg, edited by Nils Wiberg, Berlin: de Gruyter, 1995, 34th edition, ISBN 3-11-012641-9.] [cite web
last=Steel | first=Joanna | year=2007
url=http://chemistry.berkeley.edu/Publications/news/summer2006/bio_bartlett.html
title=Biography of Neil Bartlett
publisher=College of Chemistry, University of California, Berkeley
accessdate=2007-10-25] Since then, many other xenon compounds have been discovered, [cite journal
last=Bartlett | first=Neil | date=September 8, 2003
url=http://pubs.acs.org/cen/80th/noblegases.html
title=The Noble Gases | journal=Chemical & Engineering News | volume=81 | issue=36
publisher=American Chemical Society
accessdate=2007-10-01 ] and some compounds of the noble gases argon, krypton, and radon have been identified, including argon fluorohydride (HArF), [cite journal
first=Leonid | last=Khriachtchev
coauthors=Pettersson, Mika; Runeberg, Nino; Lundell, Jan; Räsänen, Markku
date = August 24, 2000
title = A stable argon compound | journal = Nature
volume = 406 | pages = 874–876 | doi = 10.1038/35022551
url = http://www.nature.com/nature/journal/v406/n6798/abs/406874a0.html
accessdate=2008-06-04 ] krypton difluoride (KrF₂), [cite book
author=Lynch, C. T.; Summitt, R.; Sliker, A.
year=1980 | title=CRC Handbook of Materials Science
publisher=CRC Press | id=ISBN 087819231X ] [cite journal
title=Krypton Difluoride: Preparation and Handling
author=D. R. MacKenzie
date=September 20, 1963 | journal=Science
volume=141 | issue= 3586 | pages=1171
doi=10.1126/science.141.3586.1171
pmid=17751791 ] and radon fluoride. [cite journal
author=Paul R. Fields, Lawrence Stein, and Moshe H. Zirin
title=Radon Fluoride
journal=Journal of the American Chemical Society
year=1962 | volume=84 | issue=21 | pages=4164–4165
doi=10.1021/ja00880a048]

Occurrence

Xenon is a trace gas in Earth's atmosphere, occurring at 0.087±0.001 parts per million (μL/L), or approximately 1 part per 11.5 million,cite book
last=Hwang | first=Shuen-Cheng
coauthors=Robert D. Lein, Daniel A. Morgan
chapter=Noble Gases
title=Kirk-Othmer Encyclopedia of Chemical Technology
publisher=Wiley | year=2005 | edition=5th edition
doi=10.1002/0471238961.0701190508230114.a01
isbn=047148511X ] and is also found in gases emitted from some mineral springs. Some radioactive species of xenon, for example, ¹³³Xe and ¹³⁵Xe, are produced by neutron irradiation of fissionable material within nuclear reactors.

Xenon is obtained commercially as a byproduct of the separation of air into oxygen and nitrogen. After this separation, generally performed by fractional distillation in a double-column plant, the liquid oxygen produced will contain small quantities of krypton and xenon. By additional fractional distillation steps, the liquid oxygen may be enriched to contain 0.1–0.2% of a krypton/xenon mixture, which is extracted either via adsorption onto silica gel or by distillation. Finally, the krypton/xenon mixture may be separated into krypton and xenon via distillation. [cite book
first=Frank G. | last=Kerry | year=2007
title=Industrial Gas Handbook: Gas Separation and Purification
pages=pp. 101–103 | publisher=CRC Press
id=ISBN 0849390052 ] [cite web
url=http://www.c-f-c.com/specgas_products/xenon.htm
title=Xenon - Xe | accessdate=2007-09-07
date=August 10, 1998 | publisher=CFC StarTec LLC] Extraction of a liter of xenon from the atmosphere requires 220 watt-hoursof energy.cite web
last=Singh | first=Sanjay | date=May 15, 2005
url=http://www.expresshealthcaremgmt.com/20050515/criticare10.shtml
title=Xenon: A modern anaesthetic
publisher=Indian Express Newspapers Limited
accessdate=2007-10-10 ] Worldwide production of xenon in 1998 was estimated at 5,000–7,000 m³.cite book
last=Häussinger | first=Peter
coauthors=Glatthaar, Reinhard; Rhode, Wilhelm;Kick, Helmut; Benkmann, Christian; Weber, Josef; Wunschel, Hans-Jörg; Stenke, Viktor; Leicht, Edith; Stenger, Hermann
chapter=Noble Gases
title=Ullmann's Encyclopedia of Industrial Chemistry
publisher=Wiley | year=2001 | edition=6th edition
doi=10.1002/14356007.a17_485 | isbn=3527201653 ] Due to its low abundance, 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 for xenon, 1 €/L for krypton, and 0.20 €/L for neon.

Xenon is relatively rare in the Sun's atmosphere, on Earth, and in asteroids and comets. The atmosphere of Mars shows a xenon abundance similar to that of Earth:0.08 parts per million, [cite web
last=Williams | first=David R.
date=September 1, 2004
url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
title=Mars Fact Sheet | publisher=NASA
accessdate=2007-10-10 ] however Mars shows a higher proportion of ¹²⁹Xe than the Earth or the Sun. As this isotope is generated by radioactive decay, the result may indicate that Mars lost most of its primordial atmosphere, possibly within the first 100 million years after the planet was formed. [cite web
last=Schilling | first=James
url=http://humbabe.arc.nasa.gov/mgcm/HTML/FAQS/thin_atm.html
title=Why is the Martian atmosphere so thin and mainly carbon dioxide?
publisher=Mars Global Circulation Model Group
accessdate=2007-10-10 ] [cite journal
last=Zahnle | first=Kevin J.
title=Xenological constraints on the impact erosion of the early Martian atmosphere
journal=Journal of Geophysical Research
year=1993 | volume=98 | issue=E6 | pages=10,899–10,913
url=http://www.agu.org/pubs/crossref/1993/92JE02941.shtml
accessdate=2007-10-10
doi=10.1029/92JE02941 ] By contrast, the planet Jupiter has an unusually high abundance of xenon in its atmosphere; about 2.6 times as much as the Sun.cite journal
last=Mahaffy | first=P. R.
coauthors=Niemann, H. B.; Alpert, A.; Atreya, S. K.; Demick, J.; Donahue, T. M.; Harpold, D. N.; Owen, T. C.
title=Noble gas abundance and isotope ratios in the atmosphere of Jupiter from the Galileo Probe Mass Spectrometer
journal=Journal of Geophysical Research
year=2000 | volume=105 | issue=E6 | pages=15061–15072
url=http://adsabs.harvard.edu/abs/2000JGR...10515061M
accessdate=2007-10-01
doi = 10.1029/1999JE001224 ] This high abundance remains unexplained and may have been caused by an early and rapid buildup of planetesimals—small, subplanetary bodies—before the presolar disk began to heat up. [cite journal
last=Owen | first=Tobias | coauthors=Mahaffy, Paul; Niemann, H. B.; Atreya, Sushil; Donahue, Thomas; Bar-Nun, Akiva; de Pater, Imke
title=A low-temperature origin for the planetesimals that formed Jupiter
journal=Nature | year=1999 | volume=402
issue=6759 | pages=269–270
url=http://adsabs.harvard.edu/abs/1999Natur.402..269O
accessdate=2007-02-04 | doi = 10.1038/46232 ] (Otherwise, xenon would not have been trapped in the planetesimal ices.) Within the Solar System, the nucleon fraction for all isotopes of xenon is 1.56 × 10^-8, or one part in 64 million of the total mass. [cite book
first=David | last=Arnett | year=1996
title=Supernovae and Nucleosynthesis
publisher=Princeton University Press
location=Princeton, New Jersey
isbn=0-691-01147-8 ] The problem of the low terrestrial xenon may potentially be explained by covalent bonding of xenon to oxygen within quartz, hence reducing the outgassing of xenon into the atmosphere. [cite journal
first=Chrystèle | last=Sanloup | coauthors="et al"
title=Retention of Xenon in Quartz and Earth's Missing Xenon
journal=Science | year=2005 | volume=310
issue=5751 | pages=1174–1177
doi= 10.1126/science.1119070
accessdate=2007-10-08
pmid=16293758 ]

Unlike the lower mass noble gases, the normal stellar nucleosynthesis process inside a star does not form xenon. Elements more massive than iron-56 have a net energy cost to produce through fusion, so there is no energy gain for a star to create xenon. [cite book
first=Donald D. | last=Clayton | year=1983
title=Principles of Stellar Evolution and Nucleosynthesis
publisher=University of Chicago Press
id=ISBN 0226109534 ] Instead, many isotopes of xenon are formed during supernova explosions.cite conference
last=Heymann | first=D. | coauthors=Dziczkaniec, M.
title =Xenon from intermediate zones of supernovae
booktitle =Proceedings 10th Lunar and Planetary Science Conference
pages =pp. 1943-1959
publisher = Pergamon Press, Inc.
date = March 19-23, 1979
location = Houston, Texas
url = http://adsabs.harvard.edu/abs/1979LPSC...10.1943H
accessdate = 2007-10-02]

Characteristics

An atom of xenon is defined as having a nucleus with 54 protons. At standard temperature and pressure, pure xenon gas has a density of 5.761 kg/m³, about 4.5 times the surface density of the Earth's atmosphere, 1.217 kg/m³. [cite web
last=Williams | first=David R. | date=April 19, 2007
url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
title=Earth Fact Sheet | publisher=NASA
accessdate=2007-10-04 ] As a liquid, xenon has a density of up to 3.100 g/mL, with the density maximum occurring at the triple point.cite book
first=Elena |last=Aprile
coauthors=Bolotnikov, Aleksey E.; Doke, Tadayoshi
title=Noble Gas Detectors |publisher=Wiley-VCH |year=2006
isbn=3527609636 |pages=8-9] Under the same conditions, the density of solid xenon, 3.640 g/cm³, is larger than the average density of granite, 2.75 g/cm³. Using gigapascals of pressure, xenon has been forced into a metallic phase. [cite journal
last = Caldwell | first = W. A.
coauthors = Nguyen, J.; Pfrommer, B.; Louie, S.; Jeanloz, R.
title = Structure, bonding and geochemistry of xenon at high pressures
journal = Science | volume = 277 | pages = 930–933
year = 1997
doi = 10.1126/science.277.5328.930 ]

Xenon 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. [cite web
last=Bader | first=Richard F. W.
url=http://miranda.chemistry.mcmaster.ca/esam/
title=An Introduction to the Electronic Structure of Atoms and Molecules
publisher=McMaster University | accessdate=2007-09-27 ] However, xenon can be oxidized by powerful oxidizing agents, and many xenon compounds have been synthesized.

In a gas-filled tube, xenon emits a blue or lavenderish glow when the gas is excited by electrical discharge. Xenon emits a band of emission lines that span the visual spectrum, [cite web
last=Talbot | first=John
url=http://web.physik.rwth-aachen.de/~harm/aixphysik/atom/discharge/index1.html
title=Spectra of Gas Discharges
publisher=Rheinisch-Westfälische Technische Hochschule Aachen
accessdate=2006-08-10 ] but the most intense lines occur in the region of blue light, which produces the coloration. [cite book
first=William Marshall | last=Watts | year=1904
title=An Introduction to the Study of Spectrum Analysis
publisher=Longmans, Green, and co.
location=London ]

Isotopes

Naturally occurring xenon is made of nine stable isotopes, the most of any element with the exception of tin, which has ten. Xenon and tin are the only elements to have more than seven stable isotopes. [cite book
first=J. B. | last=Rajam | year=1960
title=Atomic Physics | edition=7th edition
publisher=S. Chand and Co. | location=Delhi
id=ISBN 812191809X ] The isotopes ¹²⁴Xe, ¹³⁴Xe and ¹³⁶Xe are predicted to undergo double beta decay, but this has never been observed so they are considered to be stable. [cite web
last=Lüscher | first=Roland | year=2006
url=http://www.shef.ac.uk/physics/bus2006/talks/luscher_roland.pdf
title=Status of ßß-decay in Xenon
publisher=University of Sheffield
accessdate=2007-10-01 |format=PDF] [cite journal
last=Barabash | first=A. S.
title=Average (Recommended) Half-Life Values for Two-Neutrino Double-Beta Decay
journal=Czechoslovak Journal of Physics
year=2002 | volume=52 | issue=4 | pages=567–573
doi=10.1023/A:1015369612904
accessdate=2007-10-01 ] Besides these stable forms, there are over 40 unstable isotopes that have been studied. ¹²⁹Xe is produced by beta decay of ¹²⁹I, which has a half-life of 16 million years, while ^131mXe, ¹³³Xe, ^133mXe, and ¹³⁵Xe are some of the fission products of both ²³⁵U and ²³⁹Pu,cite web
last=Caldwell | first=Eric | month=January | year=2004
url=http://wwwrcamnl.wr.usgs.gov/isoig/period/xe_iig.html
title=Periodic Table--Xenon | work=Resources on Isotopes
publisher=USGS | accessdate=2007-10-08 ] and therefore used as indicators of nuclear explosions. The various isotopes of xenon are produced from supernova explosions, red giant stars that have exhausted the hydrogen at their cores and entered the asymptotic giant branch, classical novae explosions [cite journal
last=Pignatari | first=M.
coauthors=Gallino, R.; Straniero, O.; Davis, A.
title=The origin of xenon trapped in presolar mainstream SiC grains
journal=Memorie della Societa Astronomica Italiana
year=2004 | volume=75 | pages=729–734
url=http://adsabs.harvard.edu/abs/2004MmSAI..75..729P
accessdate=2007-10-26 ] and the radioactive decay of elements such as iodine, uranium and plutonium.

The artificial isotope ¹³⁵Xe is of considerable significance in the operation of nuclear fission reactors. ¹³⁵Xe has a huge cross section for thermal neutrons, 2.6×10⁶ barns,cite book
first=Weston M. | last=Stacey | year=2007
title=Nuclear Reactor Physics | pages=p. 213
publisher=Wiley-VCH | id=ISBN 3527406794 ] so it acts 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. Fortunately the designers had made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel). [cite web
author=Staff
url=http://www.cfo.doe.gov/me70/manhattan/hanford_operational.htm
title=Hanford Becomes Operational
work=The Manhattan Project: An Interactive History
publisher=U.S. Department of Energy
accessdate=2007-10-10 ] ¹³⁵Xe reactor poisoning played a major role in the Chernobyl disaster. [cite book
title=Modern Physics: An Introductory Text | year=2000
first=Jeremy I. | last=Pfeffer | coauthors=Nir, Shlomo
pages=pp. 421 ff. | publisher=Imperial College Press
id=ISBN 1860942504 ]

Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may be found emanating from nuclear reactors due to the release of fission products from cracked fuel rods, [cite book
first=Edwards A. | last=Laws | year=2000
title=Aquatic Pollution: An Introductory Text
pages=p. 505 | publisher=John Wiley and Sons
id=ISBN 0471348759 ] or fissioning of uranium in cooling water. [cite news
author=Staff | date=April 9, 1979
title=A Nuclear Nightmare | publisher=Time
url=http://www.time.com/time/magazine/article/0,9171,920196-4,00.html
accessdate=2007-10-09 ]

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. Xenon isotopic ratios such as ¹²⁹Xe/¹³⁰Xe and ¹³⁶Xe/¹³⁰Xe are also a powerful tool for understanding terrestrial differentiation and early outgassing.cite journal
last=Kaneoka | first=Ichiro
title=Xenon's Inside Story
journal=Science | year=1998 | volume=280
issue=5365 | pages=851–852
url=http://www.sciencemag.org/cgi/content/full/sci;280/5365/851b
accessdate=2007-10-10
doi=10.1126/science.280.5365.851b ] Excess ¹²⁹Xe found in carbon dioxide well gases from New Mexico was believed to be from the decay of mantle-derived gases soon after Earth's formation. [cite journal
last = Boulos | first = M.S. | coauthors = Manuel, O.K.
title = The xenon record of extinct radioactivities in the Earth.
journal = Science
volume = 174 | pages = 1334–1336 | year = 1971
doi = 10.1126/science.174.4016.1334
pmid = 17801897 ]

Compounds

:"See also: "
Xenon hexafluoroplatinate was the first chemical compound of xenon, synthesized in 1962. Following this, many additional compounds of xenon have been discovered. These include xenon difluoride (XeF₂), xenon tetrafluoride (XeF₄), xenon hexafluoride (XeF₆), xenon tetroxide (XeO₄), and sodium perxenate (Na₄XeO₆). A highly explosive compound, xenon trioxide (XeO₃), has also been made. Most of the more than 80cite web
url=http://www.chemnetbase.com/periodic_table/elements/xenon.htm
title=Xenon | work=Periodic Table Online | publisher=CRC Press
accessdate=2007-10-08 ] [cite journal
last=Moody | first=G. J.
title=A Decade of Xenon Chemistry
journal=Journal of Chemical Education
year=1974 | volume=51 | pages=628–630
url=http://www.eric.ed.gov/ERICWebPortal/recordDetail?accno=EJ111480
accessdate=2007-10-16 ] xenon compounds found to date contain electronegative fluorine or oxygen. When other atoms are bound (such as hydrogen or carbon), they are often part of a molecule containing fluorine or oxygen. [cite book
last=Harding | first=Charlie J. | coauthors=Janes, Rob
year=2002 | title=Elements of the P Block
publisher=Royal Society of Chemistry
id=ISBN 0854046909 ] Some compounds of xenon are colored but most are colorless.

In 1995, a group of scientists at the University of Helsinki in Finland (M. Räsänen and co-workers) announced the preparation of xenon dihydride (HXeH), and later xenon hydride-hydroxide (HXeOH), hydroxenoacetylene (HXeCCH), and other Xe-containing molecules. [cite journal
last=Gerber | first=R. B. | month=June | year=2004
url=http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.physchem.55.091602.094420
doi=10.1146/annurev.physchem.55.091602.094420
title=Formation of novel rare-gas molecules in low-temperature matrices
journal=Annual Review of Physical Chemistry
volume=55 | pages=55–78] [Bartlett, 2003. See the paragraph starting "Many recent findings".] Additionally, in 2008 Khriachtchev "et al." reported the preparation of HXeOXeH by the photolysis of water within a cryogenic xenon matrix. [cite journal
last=Khriachtchev | first=Leonid
coauthors=Isokoski, Karoliina; Cohen, Arik; Räsänen, Markku; Gerber, R. Benny
title=A Small Neutral Molecule with Two Noble-Gas Atoms: HXeOXeH
journal=Journal of the American Chemical Society
year=2008 | volume=130 | issue=19 | pages=6114–6118
url=http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2008/130/i19/abs/ja077835v.html
accessdate=2008-06-20
doi=10.1021/ja077835v ] Deuterated molecules, HXeOD and DXeOH, have also been produced. [cite journal
last=Pettersson | first=Mika
coauthors=Khriachtchev, Leonid; Lundell, Jan; Räsänen, Markku
title=A Chemical Compound Formed from Water and Xenon: HXeOH
journal=Journal of the American Chemical Society
year=1999 | volume=121 | issue=50 | pages=11904–11905
url=http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1999/121/i50/abs/ja9932784.html
accessdate=2007-10-10
doi=10.1021/ja9932784 ]

As well as compounds where xenon forms a chemical bond, xenon can form clathrates—substances where xenon atoms are trapped by the crystalline lattice of another compound. An example is xenon hydrate (Xe·5.75 H₂O), where xenon atoms occupy vacancies in a lattice of water molecules. [A molecular theory of general anesthesia, Linus Pauling, "Science" 134, #3471 (July 7, 1961), pp. 15–21. Reprinted as pp. 1328–1334, "Linus Pauling: Selected Scientific Papers", vol. 2, edited by Barclay Kamb et al. River Edge, New Jersey: World Scientific: 2001, ISBN 9810229402.] The deuterated version of this hydrate has also been produced. [cite journal
first=Tomoko | last=Ikeda
coauthors=Mae, Shinji; Yamamuro, Osamu; Matsuo, Takasuke; Ikeda, Susumu; Ibberson, Richard M.
title=Distortion of Host Lattice in Clathrate Hydrate as a Function of Guest Molecule and Temperature
journal=Journal of Physical Chemistry A
date=November 23, 2000 | volume=104 | issue=46
pages=10623–10630 | doi = 10.1021/jp001313j ] Such clathrate hydrates can occur naturally under conditions of high pressure,such as in Lake Vostok underneath the Antarctic ice sheet. [cite journal
last=McKay | first=C. P.
coauthors=Hand, K. P.; Doran, P. T.; Andersen, D. T.; Priscu, J. C.
title=Clathrate formation and the fate of noble and biologically useful gases in Lake Vostok, Antarctica
journal=Geophysical Letters
year=2003 | volume=30 | issue=13 | pages=35
url=http://www.agu.org/pubs/crossref/2003/2003GL017490.shtml
accessdate=2007-10-02
doi=10.1029/2003GL017490,
doi_brokendate=2008-06-25 ] Clathrate formation can be used to fractionally distill xenon, argon and krypton. [cite journal
last=Barrer | first=R. M. | coauthors=Stuart, W. I.
title=Non-Stoichiometric Clathrate of Water
journal=Proceedings of the Royal Society of London
year=1957 | volume=243 | pages=172–189 ] Xenon can also form endohedral fullerene compounds, where a xenon atom is trapped inside a fullerene molecule. The xenon atom trapped in the fullerene can be monitored via ¹²⁹Xe nuclear magnetic resonance spectroscopy. Using this technique, chemical reactions on the fullerene molecule can be analyzed, due to the sensitivity of the chemical shift of the xenon atom to its environment. However, the xenon atom also has an electronic influence on the reactivity of the fullerene. [cite journal
last=Frunzi | first=Michael
coauthors=Cross, R. James; Saunders, Martin
title=Effect of Xenon on Fullerene Reactions
journal=Journal of the American Chemical Society
year=2007 | volume=129
doi=10.1021/ja075568n | pages = 13343]

While xenon atoms are at their ground energy state, they repel each other and will not form a bond. When xenon atoms becomes energized, however, they can form an excited dimer (excimer) until the electrons return to the ground state. This entity is formed because the xenon atom tends to fill its outermost electronic shell, and can briefly do this by adding an electron from a neighboring xenon atom. The typical lifetime of a xenon excimer is 1–5 ns, and the decay releases photons with wavelengths of about 150 and 173 nm. [cite book
first=William Thomas | last=Silfvast
year=2004 | title=Laser Fundamentals
publisher=Cambridge University Press
isbn=0521833450] [cite book
first=John G. | last=Webster | year=1998
title=The Measurement, Instrumentation, and Sensors Handbook
publisher=Springer | isbn=3540648305 ] Xenon can also form dimers with other elements, such as the halogens bromine, chlorine and fluorine. [cite book
first=Charles | last=McGhee | year=1997
coauthors=Taylor, Hugh R.; Gartry, David S.; Trokel, Stephen L.
title=Excimer Lasers in Ophthalmology
publisher=Informa Health Care
isbn=1853172537 ]

Applications

Although xenon is rare and relatively expensive to extract from the Earth's atmosphere, it still has a number of applications.

Illumination and optics

Gas-discharge lamps

Xenon is used in light-emitting devices called xenon flash lamps, which are used in photographic flashes and stroboscopic lamps;cite book
first=James | last=Burke | year=2003
title=Twin Tracks: The Unexpected Origins of the Modern World
publisher=Oxford University Press
id=ISBN 0743226194 | pages=33] to excite the active medium in lasers which then generate coherent light; [cite web
author=Staff | year=2007
url=http://www.praxair.com/praxair.nsf/1928438066cae92d85256a63004b880d/32f3a328e11bb600052565660052c139?OpenDocument
title=Xenon Applications | publisher=Praxair Technology
accessdate=2007-10-04 ] and, occasionally, in bactericidal lamps. [cite journal
last=Baltás | first=E.
coauthors=Csoma, Z.; Bodai, L.; Ignácz, F.; Dobozy, A.; Kemény, L.
title=A xenon-iodine electric discharge bactericidal lamp
journal=Technical Physics Letters
year=2003 | volume=29 | issue=10 | pages=871–872
doi=10.1134/1.1623874 ] The first solid-state laser, invented in 1960, was pumped by a xenon flash lamp,cite book
last=Toyserkani | first=E.
coauthors=Khajepour, A.; Corbin, S.
pages=48
year=2004 | title=Laser Cladding
publisher=CRC Press | id=ISBN 0849321727 ] and lasers used to power inertial confinement fusion are also pumped by xenon flash lamps. [cite journal
last=Skeldon | first=M.D.
coathors=Saager, R.; Okishev, A.; Seka, W.
title=Thermal distortions in laser-diode- and flash-lamp-pumped Nd:YLF laser rods
journal=LLE Review | year=1997 | volume=71
pages=137–144
url=http://www.lle.rochester.edu/pub/review/v71/6_thermal.pdf
accessdate=2007-02-04 |format=PDF]

Continuous, short-arc, high pressure xenon arc lamps have a color temperature closely approximating noon sunlight and are used in solar simulators. That is, the chromaticity of these lamps closely approximates a heated black body radiator that has a temperature close to that observed from the Sun. After they were first introduced during the 1940s, these lamps began replacing the shorter-lived carbon arc lamps in movie projectors.cite book
first=David | last=Mellor | year=2000 | pages=p. 186
title=Sound Person's Guide to Video
publisher=Focal Press | id=ISBN 0240515951 ] They are employed in typical 35mm and IMAX film projection systems, automotive HID headlights and other specialized uses. These arc lamps are an excellent source of short wavelength ultraviolet radiation and they have intense emissions in the near infrared, which is used in some night vision systems.

The individual cells in a plasma display use a mixture of xenon and neon that is converted into a plasma using electrodes. The interaction of this plasma with the electrodes generates ultraviolet photons, which then excite the phosphor coating on the front of the display. [cite web
author=Anonymous
url=http://www.plasmatvscience.org/theinnerworkings.html
title=The plasma behind the plasma TV screen
publisher=Plasma TV Science | accessdate=2007-10-14 ] [cite news
last=Marin | first=Rick | date=March 21, 2001
title=Plasma TV: That New Object Of Desire
publisher=The New York Times ]

Xenon is used as a "starter gas" in high pressure sodium lamps. It has the lowest thermal conductivity and lowest ionization potential of all the non-radioactive noble gases. As a noble gas, it does not interfere with the chemical reactions occurring in the operating lamp. The low thermal conductivity minimizes thermal losses in the lamp while in the operating state, and the low ionization potential causes the breakdown voltage of the gas to be relatively low in the cold state, which allows the lamp to be more easily started. [cite book
first = John | last = Waymouth | year = 1971
title = Electric Discharge Lamps | publisher = The M.I.T. Press
location = Cambridge, MA | id = ISBN 0262230488 ]

Lasers

In 1962, a group of researchers at Bell Laboratories discovered laser action in xenon, [cite journal
first=C. K. N. | last=Patel
coauthors=Bennett Jr., W. R.; Faust, W. L.; McFarlane, R. A.
title=Infrared spectroscopy using stimulated emission techniques
volume=9 | issue=3 | date=August 1, 1962 | pages=102–104
journal=Physical Review Letters
url=http://prola.aps.org/abstract/PRL/v9/i3/p102_1
doi=10.1103/PhysRevLett.9.102 ] and later found that the laser gain was improved by adding helium to the lasing medium. [cite journal
first=C. K. N. | last=Patel
coauthors=Faust, W. L.; McFarlane, R. A.
title=High gain gaseous (Xe-He) optical masers
journal=Applied Physics Letters
volume=1 | number=4 | pages=84–85
date=December 1, 1962
doi=10.1063/1.1753707 ] [cite journal
first=W. R. | last=Bennett, Jr.
title=Gaseous optical masers
journal=Applied Optics Supplement
volume=1 | year=1962
pages=24–61] The first excimer laser used a xenon dimer (Xe₂) energized by a beam of electrons to produce stimulated emission at an ultraviolet wavelength of 176 nm.cite journal
url=http://www.turpion.org/php/paper.phtml?journal_id=qe&paper_id=3011
doi=10.1070/QE1971v001n01ABEH003011
last=Basov | first=N. G.
coauthors=Danilychev, V. A.; Popov, Yu. M.
title=Stimulated Emission in the Vacuum Ultraviolet Region
journal=Soviet Journal of Quantum Electronics
year=1971 | volume=1 | issue=1 | pages=18–22 ] Xenon chloride and xenon fluoride have also been used in excimer (or, more accurately, exciplex) lasers. [cite web
url=http://www.rstp.uwaterloo.ca/laser/documents/laser_types.html
title=Laser Output | publisher=University of Waterloo
accessdate=2007-10-07 ] The xenon chloride excimer laser has been employed, for example, in certain dermatological uses. [cite journal
doi=10.1111/j.1468-3083.2006.01495.x
first=E. | last=Baltás
coauthors=Csoma, Z.; Bodai, L.; Ignácz, F.; Dobozy, A.; Kemény, L.
title=Treatment of atopic dermatitis with the xenon chloride excimer laser
journal=Journal of the European Academy of Dermatology and Venereology
month=July | year=2006 | volume=20 | issue=6 | pages=657–660 ]

Anesthesia

Xenon has been used as a general anaesthetic, although it is expensive. Even so, anesthesia machines that can deliver xenon are about to appear on the European market. [cite journal
last=Tonner | first=P. H.
title=Xenon: one small step for anaesthesia…? (editorial review)
journal=Current Opinion in Anaesthesiology
year=2006 | volume=19 | issue=4
pages=382–384
doi=10.1097/01.aco.0000236136.85356.13 ] Two mechanisms for xenon anesthesia have been proposed. The first one involves the inhibition of the calcium ATPase pump—the mechanism cells use to remove calcium (Ca²⁺)—in the cell membrane of synapses. [cite journal
last=Franks first=John J.
coauthors=Horn, Jean-Louis; Janicki, Piotr K.; Singh, Gurkeerat
title=Halothane, Isoflurane, Xenon, and Nitrous Oxide Inhibit Calcium ATPase Pump Activity in Rat Brain Synaptic Plasma Membranes.
journal=Anesthesiology
year=1995 | volume=82 | issue=1
pages=108–117 | doi = 10.1097/00000542-199501000-00015 ] This results from a conformational change when xenon binds to nonpolar sites inside the protein. [cite journal
last=Lopez | first=Maria M.
coauthors=Kosk-Kosicka, Danuta
title=How do volatile anesthetics inhibit Ca₂⁺-ATPases?
journal=Journal of Biological Chemistry
year=1995 | volume=270 | issue=47
pages=28239–28245
doi=10.1074/jbc.270.47.28239
pmid=7499320 ] The second mechanism focuses on the non-specific interactions between the anesthetic and the lipid membrane. [cite journal
last=Heimburg | first=T. | coauthors=Jackson A. D.
title=The thermodynamics of general anesthesia
journal=Biophysical Journal
year=2007 | volume=92 | issue=9
pages=3159–65
doi=10.1529/biophysj.106.099754
pmid=17293400 ]

Xenon has a minimum alveolar concentration (MAC) of 71%, making it 50% more potent than N₂O as an anesthetic. Thus it can be used in concentrations with oxygen that have a lower risk of hypoxia. Unlike nitrous oxide (N₂O), xenon is not a greenhouse gas and so it is also viewed as environmentally friendly. Because of the high cost of xenon, however, economic application will require a closed system so that the gas can be recycled, with the gas being appropriately filtered for contaminants between uses.

Medical imaging

Gamma emission from the radioisotope ¹³³Xe of xenon can be used to image the heart, lungs, and brain, for example, by means of single photon emission computed tomography. ¹³³Xe has also been used to measure blood flow. [cite book
first=Ernst | last=Van Der Wall | year=1992
title=What's New in Cardiac Imaging?: SPECT, PET, and MRI
publisher=Springer | id=ISBN 0792316150 ] [cite journal
last=Frank | first=John
title=Introduction to imaging: The chest
journal=Student BMJ
year=1999 | volume=12 | pages=1–44
url=http://student.bmj.com/issues/04/01/education/8.php
accessdate=2008-06-04 ] [cite web
last=Chandak | first=Puneet K. | date=July 20, 1995
url=http://brighamrad.harvard.edu/education/online/BrainSPECT/Theory/Xenon133.html
title=Brain SPECT: Xenon-133 | publisher=Brigham RAD
accessdate=2008-06-04 ]

Nuclei of two of the stable isotopes of xenon, ¹²⁹Xe and ¹³¹Xe, have non-zero intrinsic angular momenta (nuclear spins). When mixed with alkali vapor and nitrogen and exposed to a laser beam of circularly-polarized light that is tuned to an absorption line of the alkali atoms, their nuclear spins can be aligned by a spin exchange process in which the alkali valence electrons are spin-polarized by the light and then transfer their polarization to the xenon nuclei via magnetic hyperfine coupling. [cite journal
last=Otten | first=Ernst W. | year=2004
title=Take a breath of polarized noble gas
journal=Europhysics News | volume=35 | issue=1
url=http://www.europhysicsnews.com/full/25/article9/article9.html
accessdate=2008-06-04] Typically, pure rubidium metal, heated above 100 °C, is used to produce the alkali vapor. The resulting spin polarization of xenon nuclei can surpass 50% of its maximum possible value, greatly exceeding the equilibrium value dictated by the Boltzmann distribution (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".

Because a ¹²⁹Xe nucleus has a spin of 1/2, and therefore a zero electric quadrupole moment, the ¹²⁹Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms, and thus its hyperpolarization can be maintained for long periods of time even after the laser beam has been turned off and the alkali vapor removed by condensation on a room-temperature surface. The time it takes for a collection of spins to return to their equilibrium (Boltzmann) polarization is called the "T"₁ relaxation time. For ¹²⁹Xe it can range from several seconds for xenon atoms dissolved in blood [cite journal
first=J. | last=Wolber
coauthors=Cherubini, A.; Leach, M. O.; Bifone, A.
title = On the oxygenation-dependent ¹²⁹Xe "T"₁ in blood
year = 2000 | journal = NMR in Biomedicine
volume = 13 | issue = 4 | pages = 234-237
doi = 10.1002/1099-1492(200006)13:4%3C234::AID-NBM632%3E3.0.CO;2-K
doilabel = 10.1002/1099-1492(200006)13:4<234::AID-NBM632>3.0.CO;2-K] to several hours in the gas phase [ cite journal
first=B. | last=Chann
coauthors=Nelson, I. A.; Anderson, L. W.; Driehuys, B.; Walker, T. G.
title = ¹²⁹Xe-Xe molecular spin relaxation
year = 2002 | journal = Physical Review Letters
volume = 88 | issue = 11 | pages = 113–201
doi = 10.1103/PhysRevLett.88.113201] and several days in deeply-frozen solid xenon. [cite book
first=Gustav Konrad | last=von Schulthess
coauthors=Smith, Hans-Jørgen; Pettersson, Holger; Allison, David John
year=1998 | title=The Encyclopaedia of Medical Imaging
pages= 194 | publisher=Taylor & Francis
id=ISBN 1901865134 ] In contrast, ¹³¹Xe 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. [ cite journal
first=W. W. | last=Warren | coauthors=Norberg, R. E.
title = Nuclear Quadrupole Relaxation and Chemical Shift of Xe¹³¹ in Liquid and Solid Xenon
year = 1966 | journal = Physical Review
volume = 148 | issue = 1 | pages = 402–412
doi = 10.1103/PhysRev.148.402] Hyperpolarization renders ¹²⁹Xe much more detectable via magnetic resonance imaging and has been used for studies of the lungs and other tissues. It can be used, for example, to trace the flow of gases within the lungs. [cite journal
last=Albert | first=M. S. | coauthors=Balamore, D.
title=Development of hyperpolarized noble gas MRI
journal=Nuclear Instruments and Methods in Physics Research A
year=1998 | volume=402 | pages=441–453
url=http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=11543065&dopt=AbstractPlus
accessdate=2007-10-01
doi = 10.1016/S0168-9002(97)00888-7] [cite news
last=Irion | first=Robert | date=March 23, 1999
title=Head Full of Xenon? | publisher=Science News
url=http://sciencenow.sciencemag.org/cgi/content/full/1999/323/3
accessdate=2007-10-08 ]

Other

In nuclear energy applications, xenon is used in bubble chambers, [cite book
first=Peter Louis | last=Galison | year=1997
title=Image and Logic: A Material Culture of Microphysics
pages=p. 339 | publisher=University of Chicago Press
id=ISBN 0226279170 ] probes, and in other areas where a high molecular weight and inert nature is desirable. Liquid xenon is being used as a medium for detecting hypothetical weakly interacting massive particles, or WIMPs. When a WIMP collides with a xenon nucleus, it should, theoretically, strip an electron and create a primary scintillation. By using xenon, this burst of energy could then be readily distinguished from similar events caused by particles such as cosmic rays.cite web
last=Ball | first=Philip | date=May 1, 2002
url=http://www.nature.com/news/2002/020429/full/news020429-6.html
title=Xenon outs WIMPs | publisher=Nature
accessdate=2007-10-08 ] However, the XENON experiment at the Gran Sasso National Laboratory in Italy has thus far failed to find any confirmed WIMPs. Even if no WIMPs are detected, the experiment will serve to constrain the properties of dark matter and some physics models. [cite web
last=Schumann | first=Marc | date=October 10, 2007
url=http://xenon.physics.rice.edu/
title=XENON announced new best limits on Dark Matter
publisher=Rice University | accessdate=2007-10-08 ] The current detector at this facility is five times as sensitive as other instruments world-wide, and the sensitivity will be increased by an order of magnitude in 2008. [cite news
last=Boyd | first=Jade | date=August 23, 2007
title=Rice physicists go deep for 'dark matter'
publisher=Hubble News Desk
url=http://www.media.rice.edu/media/NewsBot.asp?MODE=VIEW&ID=9902&SnID=1256234278
accessdate=2007-10-08 ]

Xenon is the preferred fuel for ion propulsion of spacecraft because of its low ionization potential per atomic weight, and its ability to be stored as a liquid at near room temperature (under high pressure) yet be easily converted back into a gas to fuel the engine. The inert nature of xenon makes it environmentally friendly and less corrosive to an ion engine than other fuels such as mercury or caesium. Xenon was first used for satellite ion engines during the 1970s. [cite web
last=Zona | first=Kathleen | date=March 17, 2006
url=http://www.nasa.gov/centers/glenn/about/fs08grc.html
title=Innovative Engines: Glenn Ion Propulsion Research Tames the Challenges of 21st century Space Travel
publisher=NASA | accessdate=2007-10-04 ] It was later employed as a propellant for Europe's SMART-1 spacecraftcite news
last=Saccoccia | first=G.
coauthors=del Amo, J. G.; Estublier, D.
date=August 31, 2006
title=Ion engine gets SMART-1 to the Moon
publisher=ESA
url=http://www.esa.int/SPECIALS/SMART-1/SEMLZ36LARE_0.html
accessdate=2007-10-01] and for the three ion propulsion engines on NASA's Dawn Spacecraft. [cite web
url=http://www.jpl.nasa.gov/news/press_kits/dawn-launch.pdf
format=PDF
title=Dawn Launch: Mission to Vesta and Ceres
publisher=NASA
accessdate=2007-10-01]

Chemically, the perxenate compounds are used as oxidizing agents in analytical chemistry. Xenon difluoride is used as an etchant for silicon, particularly in the production of microelectromechanical systems (MEMS). [cite conference
last=Brazzle | first=J. D.
coauthors=Dokmeci, M. R.; Mastrangelo, C. H.
title=Modeling and Characterization of Sacrificial Polysilicon Etching Using Vapor-Phase Xenon Difluoride
booktitle=Proceedings 17th IEEE International Conference on Micro Electro Mechanical Systems (MEMS)
pages=pp. 737-740
publisher=IEEE
date = July 28-August 1, 1975
location = Maastricht, Netherlands
isbn=9780780382657] The anticancer drug 5-fluorouracil can be produced by reacting xenon difluoride with uracil. [cite web
author=Staff | year=2007
url=http://acswebcontent.acs.org/landmarks/bartlett/tool.html
title=Powerful tool | publisher=American Chemical Society
accessdate=2007-10-10 ] Xenon is also used in protein crystallography. Applied at pressures from 0.5 to 5 MPa (5 to 50 atm) to a protein crystal, xenon atoms bind in predominantly hydrophobic cavities, often creating a high quality, isomorphous, heavy-atom derivative, which can be used for solving the phase problem. [cite web
author=Staff
date=December 21, 2004
url=http://www.srs.ac.uk/px/facilities/xenon_notes_1.html
title=Protein Crystallography: Xenon and Krypton Derivatives for Phasing
publisher=PX
accessdate=2007-10-01] [cite book
first=Jan | last=Drenth | coauthors=Mesters, Jeroen
chapter=The Solution of the Phase Problem by the Isomorphous Replacement Method
pages=123–171 | doi=10.1007/0-387-33746-6_7
title=Principles of Protein X-Ray Crystallography
publisher=Springer | location=New York
isbn= 978-0-387-33334-2 | edition=3rd edition
year=2007]

Precautions

Xenon gas can be safely kept in normal sealed glass or metal containers at standard temperature and pressure. However, it readily dissolves in most plastics and rubber, and will gradually escape from a container sealed with such materials. [cite journal
last=LeBlanc | first=Adrian D.
coauthors = Johnson, Philip C.
title = The handling of xenon-133 in clinical studies
year = 1971 | journal = Physics in Medicine and Biology
volume = 16 | issue = 1 | pages = 105-109
doi = 10.1088/0031-9155/16/1/310] Xenon is non-toxic, although it does dissolve in blood and belongs to a select group of substances that penetrate the blood-brain barrier, causing mild to full surgical anesthesia when inhaled in high concentrations with oxygen (see anesthesia subsection above). Many xenon compounds are explosive and toxic due to their strong oxidative properties. [cite web
last=Finkel | first=A. J.
coauthors=Katz, J. J.; Miller, C. E.
date=April 1, 1968
url=http://ntrs.nasa.gov/search.jsp?R=306918&id=2&qs=No%3D40%26Ne%3D26%26N%3D297%2B140%26Ns%3DPublicationYear%257C0
title=Metabolic and toxicological effects of water-soluble xenon compounds are studied
publisher=NASA | accessdate=2007-10-04 ]

At 169 m/s, the speed of sound in xenon gas is slower than that in air [169.44 m/s in xenon (at 0°C and 107 KPa), compared to 344 m/s in air. See: cite journal
last=Vacek | first=V.
coauthors=Hallewell, G.; Lindsay, S.
title=Velocity of sound measurements in gaseous per-fluorocarbons and their mixtures
journal=Fluid Phase Equilibria
year=2001 | volume=185 | pages=305–314
doi = 10.1016/S0378-3812(01)00479-4 ] (due to the slower average speed of the heavy xenon atoms compared to nitrogen and oxygen molecules), so xenon lowers the resonant frequencies of the vocal tract when inhaled. This produces a characteristic lowered voice pitch, opposite the high-pitched voice caused by inhalation of helium. Like helium, xenon does not satisfy the body's need for oxygen and is a simple asphyxiant; consequently, many universities no longer allow the voice stunt as a general chemistry demonstration. As xenon is expensive, the gas sulfur hexafluoride, which is similar to xenon in molecular weight (146 versus 131), is generally used in this stunt, although it too is an asphyxiant. [cite web
first=Steve | last=Spangler | year=2007
url=http://www.stevespanglerscience.com/experiment/from-donald-duck-to-barry-white-how-gases-change-your-voice
title=Anti-Helium - Sulfur Hexafluoride
publisher=Steve Spangler Science
accessdate=2007-10-04 ]

It is possible to safely breathe heavy gases such as xenon or sulfur hexafluoride when they include a 20% mixture of oxygen (although xenon at this concentration would be expected to produce the unconsciousness of general anesthesia). The lungs mix the gases very effectively and rapidly, so that the heavy gases are purged along with the oxygen and do not accumulate at the bottom of the lungs. [cite journal
last=Yamaguchi | first=K.
coauthors=Soejima, K.; Koda, E.; Sugiyama, N
title=Inhaling Gas With Different CT Densities Allows Detection of Abnormalities in the Lung Periphery of Patients With Smoking-Induced COPD
journal=Chest Journal
year=2001 | volume=51 | pages=1907–1916
doi= 10.1378/chest.120.6.1907
accessdate=2007-10-16
pmid=11742921 ] There is, however, a danger associated with any heavy gas in large quantities: it may sit invisibly in a container, and if a person enters a container filled with an odorless, colorless gas, they may find themselves breathing it unknowingly. Xenon is rarely used in large enough quantities for this to be a concern, though the potential for danger exists any time a tank or container of xenon is kept in an unventilated space. [cite web
author=Staff | date=August 1, 2007
url=http://www-group.slac.stanford.edu/esh/hazardous_substances/cryogenic/p_hazards.htm
title=Cryogenic and Oxygen Deficiency Hazard Safety
publisher=Stanford Linear Accelerator Center
accessdate=2007-10-10 ]

ee also

* Penning mixture

References

External links

* [http://www.webelements.com/webelements/elements/text/Xe/index.html WebElements.com – Xenon]
* [http://wwwrcamnl.wr.usgs.gov/isoig/period/xe_iig.html USGS Periodic Table - Xenon]
* [http://environmentalchemistry.com/yogi/periodic/Xe.html EnvironmentalChemistry.com - Xenon]
* [http://www.anaesthetist.com/anaes/drugs/xenon.htm Xenon as an anesthetic]