Iridium-191

Main isotopes of iridium

Iso­tope Decay abun­dance half-life mode energy (MeV) pro­duct 188Ir syn 1.73 d ε 1.64 188Os 189Ir syn 13.2 d ε 0.532 189Os 190Ir syn 11.8 d ε 2.000 190Os 191Ir 37.3% is stable with 114 neutrons 192Ir syn 73.827 d β− 1.460 192Pt ε 1.046 192Os 192m2Ir syn 241 y IT 0.161 192Ir 193Ir 62.7% is stable with 116 neutrons 193mIr syn 10.5 d IT 0.080 193Ir 194Ir syn 19.3 h β− 2.247 194Pt 194m2Ir syn 171 d IT – 194Ir
Standard atomic weight (Ar)	192.217(3)

There are two natural isotopes of iridium (₇₇Ir), and 34 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.

Iridium-192 (symbol ¹⁹²Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days. 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.

Iridium-192 is also a strong gamma ray emitter. There are seven principal energy packets produced during its disintegration process ranging from just over 0.2 to about 0.6 MeV. Iridium-192 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.

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