Bismuth-209 (209Bi) is an
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[2] of 126 neutrons,[2] and an atomic mass of 208.9803987
amu (atomic mass units).
Primordial bismuth consists entirely of this isotope.
Theory had previously predicted a half-life of 4.6×1019 years. It had been suspected to be radioactive for a long time.[6] The decay produces a 3.14 MeV
alpha particle plus
thallium-205.[3][4]
If perturbed, it would join in lead-bismuth neutron capture cycle from lead-206/207/208 to bismuth-209, despite low capture cross sections. Even thallium-205, the decay product of bismuth-209, reverts to lead when fully ionized.[8]
Due to its hugely long half-life, for nearly all applications 209Bi can be treated as non-radioactive. It is much less radioactive than human flesh, so it poses no real radiation hazard. Though 209Bi holds the half-life record for alpha decay, it does not have the longest known half-life of any nuclide; this distinction belongs to
tellurium-128 (
128Te) with a half-life estimated at 7.7 × 1024 years by double β-decay (
double beta decay).[9][10][11]
The half-life of 209Bi was confirmed in 2012 by an Italian team in
Gran Sasso who reported (2.01±0.08)×1019 years. They also reported an even longer half-life for alpha decay of 209Bi to the first excited state of 205Tl (at 204 keV), was estimated at 1.66×1021 years.[12] Even though this value is shorter than the half-life of 128Te, both alpha decays of 209Bi 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~1.3×10−44 eV in application of the
uncertainty principle[13] (double beta decay would produce energy lines only in
neutrinoless transitions, which has not been observed yet).
Applications
Because all primordial bismuth is bismuth-209, bismuth-209 is used for all normal applications of bismuth, such as being used as a replacement for
lead,[14][15] in cosmetics,[16][17] in paints,[18] and in several medicines such as
Pepto-Bismol.[5][19][20] Alloys containing bismuth-209 such as
bismuth bronze have been used for thousands of years.[21]
Synthesis of other elements
210Po can be manufactured by bombarding 209Bi with
neutrons in a nuclear reactor.[22] Only around 100 grams of 210Po are produced each year.[23][22]209Po and 208Po can be made through the proton bombardment of 209Bi in a
cyclotron.[24]Astatine can also be produced by bombarding 209Bi with alpha particles.[25][26][27] Traces of 209Bi have also been used
to creategold in nuclear reactors.[28][29]
In 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,[44] and the latter quickly decays.[44] All elements heavier than it are formed in the
r-process, or rapid process, which occurs during the first fifteen minutes of
supernovas.[45][44] Bismuth-209 is also created during the r-process.[44]
^Red horizontal lines with a circle in their right ends represent
neutron captures; blue arrows pointing up-left represent
beta decays; green arrows pointing down-left represent
alpha decays; cyan/light-green arrows pointing down-right represent
electron captures.
^
abMarcillac, Pierre de; Noël Coron; Gérard Dambier; Jacques Leblanc; Jean-Pierre Moalic (April 2003). "Experimental detection of α-particles from the radioactive decay of natural bismuth". Nature. 422 (6934): 876–878.
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^
abKean, Sam (2011). The Disappearing Spoon (and other true tales of madness, love, and the history of the world from the Periodic Table of Elements). New York/Boston: Back Bay Books. pp. 158–160.
ISBN978-0-316-051637.
^Carvalho, H. G.; Penna, M. (1972). "Alpha-activity of 209 Bi ". Lettere al Nuovo Cimento. 3 (18): 720.
doi:
10.1007/BF02824346.
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^"Noble Gas Research". Archived from
the original on 2011-09-28. Retrieved 2013-01-10. Tellurium-128 information and half-life. Accessed July 14, 2009.
^B. Gunter "Inorganic Colored Pigments” in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012.
^Madisch A, Morgner A, Stolte M, Miehlke S (December 2008). "Investigational treatment options in microscopic colitis". Expert Opinion on Investigational Drugs. 17 (12): 1829–37.
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^Larsen, R. H.; Wieland, B. W.; Zalutsky, M. R. J. (1996). "Evaluation of an Internal Cyclotron Target for the Production of 211At via the 209Bi (α,2n)211At reaction". Applied Radiation and Isotopes. 47 (2): 135–143.
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^
abMunzenberg; Hofmann, S.; Heßberger, F. P.; Reisdorf, W.; Schmidt, K. H.; Schneider, J. H. R.; Armbruster, P.; Sahm, C. C.; Thuma, B. (1981). "Identification of element 107 by α correlation chains". Z. Phys. A. 300 (1): 107–108.
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^Hofmann, S.; Ninov, V.; Heßberger, F. P.; Armbruster, P.; Folger, H.; Münzenberg, G.; Schött, H. J.; Popeko, A. G.; et al. (1995). "The new element 111". Zeitschrift für Physik A. 350 (4): 281–282.
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^Hofmann, S.; Heßberger, F. P.; Ackermann, D.; Münzenberg, G.; Antalic, S.; Cagarda, P.; Kindler, B.; Kojouharova, J.; et al. (2002). "New results on elements 111 and 112". The European Physical Journal A. 14 (2): 147–157.
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