214Bi

Bismuth-214 (214Bi) is a radioactive isotope of the element bismuth (atomic number 83) with a mass number of 214. It occurs in the natural uranium-238 decay chain, where it is produced from lead-214 by beta decay. In secular equilibrium with its parent nuclides, 214Bi activity reflects the activity of the uranium-238 series in a given sample.

The half-life of 214Bi is about 19.9 minutes. Its decay is dominated by beta minus emission to polonium-214 (Po-214), which in turn decays via alpha emission to lead-210 (Pb-210). A much smaller alpha-decay branch has been observed but plays a negligible role in most practical contexts. Thus 214Bi is typically a beta-emitting step in the chain that ultimately leads to stable lead-206.

214Bi is a significant gamma emitter. It produces several prominent gamma rays that are commonly detected in gamma spectroscopy, with intensities associated with energies such as roughly 609 keV, 1120 keV, and 1764 keV. These gamma lines enable identification and quantification of 214Bi in environmental samples, radioactive sources, and during radiological monitoring.

Occurrence and significance: 214Bi is found in materials containing uranium and in environments where the uranium-238 decay chain is present, including ores, nuclear fuel, and certain industrial or geological samples. Its relatively short half-life means its activity can fluctuate with changes in the parent activities, but its gamma emissions make it a useful indicator of natural radioactivity and a contributor to external dose in contaminated environments.

See also: uranium-238 decay chain, polonium-214, lead-210, gamma spectroscopy.