Bismuth-209

Template:Short description Template:Infobox isotope Bismuth-209 (Template:SupBi) is an isotope of bismuth with the longest known half-life of any nuclide that undergoes α-decay (alpha decay); the decay product is thallium-205. It has 83 protons and a magic number of 126 neutrons, and naturally occurring bismuth consists entirely of this isotope.

Decay properties

Bismuth-209 was long thought to have the heaviest stable nucleus of any element, but in 2003, a research team at the Template:Ill in Orsay, France, discovered that Template:SupBi undergoes alpha decay with a half-life now given more precisely as Template:Val years (20.1 quintillion years), over 10Template:Sup times longer than the estimated age of the universe. The heaviest nucleus considered to be stable is now lead-208 and the heaviest stable monoisotopic element is gold (gold-197).

Theory had previously predicted a half-life of 4.6Template:E years. It had been suspected to be radioactive for a long time. The decay produces a 3.14 MeV alpha particle plus thallium-205.

Bismuth-209 occurs in the neptunium series decay chain.

Due to its extremely long half-life, Template:SupBi can be treated as non-radioactive for nearly all applications. It is much less radioactive than human flesh, so it poses no real radiation hazard. Though Template:SupBi 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 ([[tellurium-128|Template:SupTe]]) with a half-life estimated at Template:Val years by double beta decay.

The half-life of Template:SupBi was confirmed in 2012 by an Italian team in Gran Sasso who reported Template:Val years. They also reported an even longer partial half-life for alpha decay of Template:SupBi to the first excited state of Template:SupTl (at 204 keV), estimated at 1.66Template:E years. Even though this value is shorter than the half-life of Template:SupTe, both alpha decays of Template:SupBi hold the record of the thinnest natural line widths of any measurable physical excitation, estimated respectively at ΔΕ ≈ Template:Val and ΔΕ ≈ Template:Val in application of the uncertainty principle $\mathrm{\Delta }E=\frac{\hslash }{2T_{1/2}}$ (beta or double beta decay would produce energy lines only in neutrinoless transitions, which have never been observed).

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, in cosmetics, in paints, and in several medicines such as Pepto-Bismol. Alloys containing bismuth-209 such as bismuth bronze have been used for thousands of years.

Synthesis of other elements

[[Polonium-210|Template:SupPo]] can be manufactured by bombarding Template:SupBi with neutrons in a nuclear reactor and around 100 grams of Template:SupPo are produced each year. [[Isotopes of polonium|Template:SupPo and Template:SupPo]] can be made through the proton bombardment of Template:SupBi in a cyclotron. Astatine can also be produced by bombarding Template:SupBi with alpha particles. Traces of Template:SupBi have also been used to create gold in nuclear reactors.

Template:SupBi has been used as a target for the creation of several isotopes of superheavy elements such as dubnium, bohrium, meitnerium, roentgenium, and nihonium.

Formation

Primordial

Bismuth-209 is created in the final part of the s-process.Template:Efn

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 supernovae. Bismuth-209 is also created during the r-process.

Radiogenic

Some Template:SupBi was created radiogenically from the neptunium decay chain. Neptunium-237 is an extinct radionuclide, but it can be found in traces in uranium ores because of neutron capture reactions. This is also ultimately due to the r-process, as every (4n+1) nucleus formed (and not fissioned) ultimately decayed to bismuth.

See also

• Isotopes of bismuth
• Primordial radionuclide
• List of elements by stability of isotopes