Bismuth-209
Bismuth-209 (209Bi) 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.
| General | |
|---|---|
| Symbol | 209Bi |
| Names | bismuth-209, Bi-209 |
| Protons | 83 |
| Neutrons | 126 |
| Nuclide data | |
| Natural abundance | 100% |
| Half-life | 2.01×1019 years[1] |
| Parent isotopes | 209Pb (β−) 209Po (β+) 213At (α) |
| Decay products | 205Tl |
| Isotope mass | 208.9803987 u |
| Spin | 9/2− |
| Excess energy | −18 258.461± 2.4 keV |
| Binding energy | 7847.987± 1.7 keV |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| Alpha emission | 3.1373 |
| Isotopes of bismuth Complete table of nuclides | |
Decay propertiesEdit
Bismuth-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, approximately 19 quintillion years), over a billion times longer than the current estimated age of the universe. The heaviest nucleus considered to be stable is now lead-208. Theory had previously predicted a half-life of 4.6×1019 years. The decay event produces a 3.14 MeV alpha particle and converts the atom to thallium-205.[2][3]
Bismuth-209 will eventually form 205Tl if unperturbed:
- 209
83Bi
→ 205
81Tl
+ 4
2He
[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 in thallium-205 case above, once fully ionized, again reverts to lead.
Due to its extraordinarily long half-life, for nearly all applications 209Bi can still be treated as if it were non-radioactive. Its radioactivity is much slighter than that of human flesh, so it poses no meaningful hazard from radiation. 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 (double beta decay).[5]
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 204 keV, was estimated to be 1.66×1021 years.[6] Even though 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~1.3×10−44 eV in application of the uncertainty principle of Heisenberg[7] (double beta decay would produce energy lines only in neutrinoless transitions, which has not been observed yet).
UsesEdit
210Po can be manufactured by bombarding 209Bi with neutrons in a nuclear reactor. Only some 100 grams of 210Po are produced each year.[8]
FormationEdit
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, 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.[9]
See alsoEdit
NotesEdit
| Lighter: bismuth-208 |
Bismuth-209 is an isotope of bismuth |
Heavier: bismuth-210 |
| Decay product of: astatine-213 (α) polonium-209 (β+) lead-209 (β−) |
Decay chain of bismuth-209 |
Decays to: thallium-205 (α) |
ReferencesEdit
- ^ Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
- ^ Dumé, Belle (2003-04-23). "Bismuth breaks half-life record for alpha decay". Physicsweb.
- ^ Marcillac, 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. Bibcode:2003Natur.422..876D. doi:10.1038/nature01541. PMID 12712201.
- ^ "Isotope data for americium-241 in the Periodic Table".
- ^ "Archived copy". Archived from the original on 2011-09-28. Retrieved 2013-01-10.CS1 maint: archived copy as title (link) Tellurium-128 information and half-life. Accessed July 14, 2009.
- ^ J.W. Beeman; et al. (2012). "First Measurement of the Partial Widths of 209Bi Decay to the Ground and to the First Excited States". Physical Review Letters. 108 (6): 062501. arXiv:1110.3138. doi:10.1103/PhysRevLett.108.062501. PMID 22401058.
- ^ "Particle lifetimes from the uncertainty principle".
- ^ "Swiss study: Polonium found in Arafat's bones". Al Jazeera. Retrieved 2013-11-07.
- ^ Chaisson, Eric, and Steve McMillan. Astronomy Today. 6th ed. San Francisco: Pearson Education, 2008.