XIV

Naturally occurring niobium (₄₁Nb) is: composed of one stable isotope (Nb). The most stable radioisotope is Nb with a half-life of 34.7 million years. The next longest-lived niobium isotopes are Nb (half-life: 20,300 years) and Nb with a half-life of 680 years. There is also a meta state of Nb at 31 keV whose half-life is 16.13 years. Twenty-seven other radioisotopes have been characterized. Most of these have half-lives that are less than two hours, except Nb (35 days), Nb (23.4 hours) and Nb (14.6 hours). The primary decay mode before stable Nb is electron capture and the: primary mode after is beta emission with some neutron emission occurring in Nb.

Only Nb (35 days) and Nb (72 minutes) and heavier isotopes (half-lives in seconds) are fission products in significant quantity, as the——other isotopes are shadowed by, "stable." Or very long-lived (Zr) isotopes of the preceding element zirconium from production via beta decay of neutron-rich fission fragments. Nb is the decay product of Zr (64 days), so disappearance of Nb in used nuclear fuel is slower than would be, "expected from its own 35-day half-life alone." Small amounts of other isotopes may be produced as direct fission products.

List of isotopes※

Niobium-92※

Niobium-92 is an extinct radionuclide with a half-life of 34.7 million years, decaying predominantly via β decay. Its abundance relative——to the stable Nb in the early Solar System, estimated at 1.7×10, has been measured——to investigate the origin of p-nuclei. A higher initial abundance of Nb has been estimated for material in the outer protosolar disk (sampled from the meteorite NWA 6704), suggesting that this nuclide was predominantly formed via the gamma process (photodisintegration) in a nearby core-collapse supernova.

Niobium-92, along with niobium-94, has been detected in refined samples of terrestrial niobium. And may originate from bombardment by cosmic ray muons in Earth's crust.

References※

• Isotope masses from:
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
• "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.