There are two natural isotopes of iridium (77Ir), and 37 radioisotopes, the most stable radioisotope being 192Ir with a half-life of 73.83 days, and many nuclear isomers, the most stable of which is 192m2Ir with a half-life of 241 years. All other isomers have half-lives under a year, most under a day. All isotopes of iridium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.[4]
^( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^ abc# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
Iridium-192 (symbol 192Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.[11] It decays by emitting beta (β) particles and gamma (γ) radiation. About 96% of 192Ir decays occur via emission of β and γ radiation, leading to 192Pt. Some of the β particles are captured by other 192Ir nuclei, which are then converted to 192Os. Electron capture is responsible for the remaining 4% of 192Ir decays.[12] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal.[13]
Iridium-192 is a very strong gamma ray emitter, with a gamma dose-constant of approximately 1.54 μSv·h−1·MBq−1 at 30 cm, and a specific activity of 341 TBq·g−1 (9.22 kCi·g−1).[14][15] There are seven principal energy packets produced during its disintegration process ranging from just over 0.2 to about 0.6 MeV.
The 192m2Ir isomer is unusual, both for its long half-life for an isomer, and that said half-life greatly exceeds that of the ground state of the same isotope.
^Drummond, M. C.; O'Donnell, D.; Page, R. D.; Joss, D. T.; Capponi, L.; Cox, D. M.; Darby, I. G.; Donosa, L.; Filmer, F.; Grahn, T.; Greenlees, P. T.; Hauschild, K.; Herzan, A.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Lopez-Martens, A.; Mistry, A. K.; Nieminen, P.; Peura, P.; Rahkila, P.; Rinta-Antila, S.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Sayğı, B.; Scholey, C.; Simpson, J.; Sorri, J.; Thornthwaite, A.; Uusitalo, J. (16 June 2014). "α decay of the π h 11 / 2 isomer in Ir 164". Physical Review C. 89 (6): 064309. Bibcode:2014PhRvC..89f4309D. doi:10.1103/PhysRevC.89.064309. ISSN0556-2813. Retrieved 21 June 2023.
^Drummond, M. C.; O'Donnell, D.; Page, R. D.; Joss, D. T.; Capponi, L.; Cox, D. M.; Darby, I. G.; Donosa, L.; Filmer, F.; Grahn, T.; Greenlees, P. T.; Hauschild, K.; Herzan, A.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Lopez-Martens, A.; Mistry, A. K.; Nieminen, P.; Peura, P.; Rahkila, P.; Rinta-Antila, S.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Sayğı, B.; Scholey, C.; Simpson, J.; Sorri, J.; Thornthwaite, A.; Uusitalo, J. (16 June 2014). "α decay of the π h 11 / 2 isomer in Ir 164". Physical Review C. 89 (6): 064309. Bibcode:2014PhRvC..89f4309D. doi:10.1103/PhysRevC.89.064309. ISSN0556-2813. Retrieved 21 June 2023.
^ abcdJaniak, Ł.; Gierlik, M.; Kosinski, T.; Matusiak, M.; Madejowski, G.; Wronka, S.; Rzadkiewicz, J. (2024). "Half-life of 190Ir". Physical Review C. 110 (014306). doi:10.1103/PhysRevC.110.014306.
