Iridium-192

{{Short description|Radioactive isotope of iridium}} {{Infobox isotope | name = Iridium-192 | image = | image_caption = | alternate_names = | mass_number = 192 | symbol = Ir | num_neutrons = 115 | num_protons = 77 | abundance = synthetic | halflife = 73.82 days<ref name="nubase">{{NUBASE2020}}</ref> | decay_product = Platinum-192 | decay_mass = 192 | decay_symbol = Pt | decay_product2 = Osmium-192 | decay_mass2 = 192 | decay_symbol2 = Os | parent = Osmium-192 | parent_mass = 192m | parent_symbol = Os | parent_decay = β^&minus; | parent2 = | parent2_mass = | parent2_symbol = | parent2_decay = | parent3 = | parent3_mass = | parent3_symbol = | parent3_decay = | mass = 191.962605<ref>{{AME2020 II}}</ref> | spin = 4+ | excess_energy = | binding_energy = | decay_mode1 = β⁻ | decay_energy1 = | decay_mode2 = ε | decay_energy2 = | decay_mode3 = | decay_energy3 = | decay_mode4 = | decay_energy4 = }}

'''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.<ref>{{Cite web|url=https://www.isoflex.com/products/radioisotopes/iridium-isotopes|title=Isotope Supplier: Stable Isotopes and Radioisotopes from ISOFLEX - Iridium-192|website=www.isoflex.com|language=en|access-date=2017-10-11}}</ref> Iridium-192 is a very strong gamma ray emitter, with a gamma dose constant of 1.54 μSv·h⁻¹·MBq⁻¹ at 30&nbsp;cm, and a specific activity of 341 TBq·g⁻¹ (9.22 kCi·g⁻¹).<ref>{{cite journal |last1=Delacroix |first1=D |last2=Guerre |first2=J P |last3=Leblanc |first3=P |last4=Hickman |first4=C |title=Radionuclide and Radiation Protection Data Handbook |journal=Radiation Protection Dosimetry |date=2002 |volume=98 |issue=1 |pages=9–168 |publisher=Nuclear Technology Publishing |location=Ashford, Kent |doi=10.1093/OXFORDJOURNALS.RPD.A006705 |pmid=11916063 |isbn=1870965876 |s2cid=123447679 |edition=2nd |url=https://pdfs.semanticscholar.org/fbb1/7281dae98db83fe20df96b9d879c0c73b199.pdf |archive-url=https://web.archive.org/web/20190822130507/https://pdfs.semanticscholar.org/fbb1/7281dae98db83fe20df96b9d879c0c73b199.pdf |url-status=dead |archive-date=2019-08-22 }}</ref><ref>{{cite report|last1=Unger |first1=L M |last2=Trubey |first2=D K |title=Specific Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological Assessment |url=https://www.orau.org/documents/ivhp/health-physics/ornl-rsic-45.pdf |publisher=Oak Ridge National Laboratory|date=May 1982 |archive-url=https://web.archive.org/web/20180322020815/https://www.orau.org/documents/ivhp/health-physics/ornl-rsic-45.pdf |archive-date=22 March 2018}}</ref> 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.<ref>{{NNDC}}</ref> It is commonly used as a gamma ray source in industrial radiography to locate flaws in metal components.<ref>{{cite book |author=Charles Hellier |title=Handbook of Nondestructive Evaluation |publisher=McGraw-Hill |year=2003 |isbn=978-0-07-028121-9|page=6.20}}</ref> 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.<ref>{{cite magazine |magazine=The New Yorker|title=The Unthinkable|author= Steve Coll |date= March 12, 2007|access-date=2007-03-09|url= https://www.newyorker.com/reporting/2007/03/12/070312fa_fact_coll?printable=true}}</ref>

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&nbsp;years,<ref name="nubase"/> which is somewhat unusual for its long half-life and that said half-life greatly exceeds that of the ground state.

== See also ==

*Isotopes of iridium

== References == {{reflist}}

Category:Isotopes of iridium