linguistic:translation
Isotopes

The only primordial isotope of bismuth, bismuth-209, was regarded as the heaviest stable nuclide, but it had long been suspected to be unstable on theoretical grounds. This was finally demonstrated in 2003, when researchers at the Institut d'astrophysique spatiale in Orsay, France, measured the alpha (α) decay half-life of Bi to be 2.01 × 10 years (3 Bq /Mg), over 10 x longer than the estimated age of the universe. Due to its hugely long half-life, for all known medical and industrial applications, bismuth can be treated as stable. The radioactivity is of academic interest because bismuth is one of a few elements whose radioactivity was suspected and theoretically predicted before being detected in the laboratory. Bismuth has the longest known α-decay half-life, though tellurium-128 has a double beta decay half-life of over 2.2 × 10 years. Bismuth's extremely long half-life means that less than 1/10 of the bismuth present when the Earth formed, has decayed into thallium since then.

Six isotopes of bismuth with short half-lives (210–215 inclusive) occur in the natural radioactive decay chains of actinium, radium, thorium, and neptunium; and more have been synthesized. (Though all primordial Np has long since decayed, it is continually regenerated by (n,2n) knockout reactions on natural U.)

Commercially, bismuth-213 can be produced by bombarding radium with bremsstrahlung photons from a linear particle accelerator. In 1997, an antibody conjugate with bismuth-213, which has a 45-minute half-life and α-decays, was used to treat leukemia patients. This isotope has also been tried in cancer treatment, for example, in the targeted alpha therapy (TAT) program.