| 词条 | Bismuth-209 |
| 释义 |
|alternate_names = Bismuth-209 |mass_number = 209 |symbol = Bi |num_neutrons = 126 |num_protons = 83 |abundance = 100% |mass = 208.9803987 |spin = 9/2− |halflife = 1.9{{e|19}} years |decay_mode1 = Alpha emission | decay_energy1 = 3.1373 |decay_product = thallium-205 |decay_symbol = Tl |decay_mass = 205 |excess_energy = −18 258.461 |error1 = 2.4 |binding_energy = 7847.987 |error2 = 1.7 |parent= lead-209 |parent_symbol=Pb |parent_mass=209 |parent_decay=b |parent2= polonium-209 |parent2_symbol=Po |parent2_mass=209 |parent2_decay=b+ |parent3= astatine-213 |parent3_symbol=At |parent3_mass=213 |parent3_decay=a }} Bismuth-209 is the isotope of bismuth with the longest known half-life of any radioisotope that undergoes α-decay (alpha decay). It has 83 protons and a magic number of 126 neutrons, and an atomic mass of 208.9803987 amu (atomic mass units). Primordial bismuth consists entirely of this isotope. Decay propertiesBismuth-209 was long thought to have the heaviest stable nucleus of any element, but in 2003, a research team at the Institut d’Astrophysique Spatiale in Orsay, France, discovered that 209Bi undergoes alpha decay with a half-life of approximately 19 exayears (1.9×1019 which is 19 quintillion years), over a billion times longer than the current estimated age of the universe. Theory had previously predicted a half-life of 4.6{{e|19}} years. The decay event produces a 3.14 MeV alpha particle and converts the atom to thallium-205.[1][2] Bismuth-209 will eventually form 205Tl: {{nuclide|bismuth|209}} → {{nuclide|thallium|205}} + {{nuclide|helium|4}}[3] Due to its extraordinarily long half-life, for nearly all applications 209Bi can still be treated as if it were non-radioactive. Although 209Bi holds the half-life record for alpha decay, bismuth does not have the longest half-life of any radionuclide to be found experimentally—this distinction belongs to tellurium-128 (128Te) with a half-life estimated at 7.7 × 1024 years by double β-decay (beta decay).[4] The half-life value of Bismuth-209 was confirmed in 2012 by an italian team in Gran Sasso who reported 2.01±0.08 ×1019 years, and an even longer half-life, for bismuth-209 alpha decay to the first excited state of Thalium-205 at 204keV, which was estimated to be 1.66{{e|21}} years.[5] Even if this value is shorter than the measured half-life of tellurium-128, both alpha decays of Bismuth-209 hold the record of the thinnest natural line widths of any measurable physical excitation, estimated respectively at ΔΕ~5.5×10−43 eV and ΔΕ~1.3×10−44eV in application of the uncertainty principle of Heisenberg [6] (double beta decay would produce energy lines only in neutrinoless transitions, which has not been observed yet). Uses210Po can be manufactured by bombarding 209Bi with neutrons in a nuclear reactor. Only some 100 grams of 210Po are produced each year.[7]FormationIn the red giant stars of the asymptotic giant branch, the s-process (slow process) is ongoing to produce bismuth-209 and polonium-210 by neutron capture as the heaviest elements to be formed, and the latter quickly decays. All elements heavier than it are formed in the r-process, or rapid process, which occurs during the first fifteen minutes of supernovas.[8] See also
Notes1. ^{{cite news|url = http://physicsworld.com/cws/article/news/2003/apr/23/bismuth-breaks-half-life-record-for-alpha-decay|title = Bismuth breaks half-life record for alpha decay|date = 2003-04-23|publisher = Physicsweb|first = Belle|last = Dumé}} {{Isotope|element=bismuth2. ^{{cite journal | last = Marcillac | first = Pierre de |author2=Noël Coron |author3=Gérard Dambier |author4=Jacques Leblanc |author5=Jean-Pierre Moalic |date=April 2003 | title = Experimental detection of α-particles from the radioactive decay of natural bismuth | journal = Nature | volume = 422 | pages = 876–878 | doi = 10.1038/nature01541 | pmid = 12712201 | issue = 6934 | bibcode=2003Natur.422..876D}} 3. ^http://periodictable.com/Isotopes/095.241/index.full.html 4. ^{{cite web|url=http://presolar.wustl.edu/work/noblegas.html |title=Archived copy |accessdate=2013-01-10 |deadurl=yes |archiveurl=https://web.archive.org/web/20110928143717/http://presolar.wustl.edu/work/noblegas.html |archivedate=2011-09-28 |df= }} Tellurium-128 information and half-life. Accessed July 14, 2009. 5. ^{{Cite journal|last=J.W. Beeman|display-authors=et al|date=2012|title=First Measurement of the Partial Widths of 209Bi Decay to the Ground and to the First Excited States|url=|journal=Phys. Rev. Letters 108(6) 062501|volume=|pages=|via=}} 6. ^{{Cite web|url=http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/parlif.html|title=Particle lifetimes from the uncertainty principle|last=|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=}} 7. ^{{cite web |url = http://www.aljazeera.com/investigations/killing-arafat/swiss-study-polonium-found-arafats-bones-201311522578803512.html |title = Swiss study: Polonium found in Arafat’s bones | publisher = Al Jazeera| accessdate = 2013-11-07}} 8. ^Chaisson, Eric, and Steve McMillan. Astronomy Today. 6th ed. San Francisco: Pearson Education, 2008. |lighter=bismuth-208 |heavier=bismuth-210 |before=astatine-213 (α) polonium-209 (β+) lead-209 (β−) |after=thallium-206 (α)}} References{{reflist}} 1 : Isotopes of bismuth |
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