Iridium-192 (symbol 192Ir) is a radioactive isotope of iridium, with a half-life of 73.82 days. It decays by emitting beta (β) particles and gamma (γ) radiation. 95.24% of 192Ir decays occur via β- emission, leading to 192Pt; the remaining 4.76% occur via electron capture to 192Os; both modes involve gamma emission. Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal. Iridium-192 is a very strong gamma ray emitter, with a gamma dose constant of 1.54 μSv·h−1·MBq−1 at 30 cm, and a specific activity of 341 TBq·g−1 (9.22 kCi·g−1). There are seven principal gamma rays produced in its beta-minus decay, ranging from 296.0 to 612.5 keV, and two produced in its electron capture decay at 205.8 and 484.6 keV. It is commonly used as a gamma ray source in industrial radiography to locate flaws in metal components. It is also used in radiotherapy as a radiation source, in particular in brachytherapy. Iridium-192 has accounted for the majority of cases tracked by the U.S. Nuclear Regulatory Commission in which radioactive materials have gone missing in quantities large enough to make a dirty bomb.
| General | |
|---|---|
| Symbol | 192Ir |
| Names | Iridium-192 |
| Protons (Z) | 77 |
| Neutrons (N) | 115 |
| Nuclide data | |
| Natural abundance | synthetic |
| Half-life (t1/2) | 73.82 days |
| Isotope mass | 191.962605 Da |
| Spin | 4+ |
| Parent isotopes | 192mOs (β−) |
| Decay products | 192Pt 192Os |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| Isotopes of iridium Complete table of nuclides | |
The metastable isomer 192m2Ir is iridium's most stable isomer. It decays solely by isomeric transition (to this ground state) with a half-life of 241 years, which is somewhat unusual for its long half-life and that said half-life greatly exceeds that of the ground state.
See also
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