Isotopes of iridium (77Ir)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
188Ir synth 1.73 d ε 188Os
189Ir synth 13.2 d ε 189Os
190Ir synth 11.8 d ε 190Os
191Ir 37.3% stable
192Ir synth 73.827 d β− 192Pt
ε 192Os
192m2Ir synth 241 y IT 192Ir
193Ir 62.7% stable
193mIr synth 10.5 d IT 193Ir
194Ir synth 19.3 h β− 194Pt
194m2Ir synth 171 d IT 194Ir
Standard atomic weight Ar°(Ir)
  • 192.217±0.002
  • 192.22±0.01 (abridged)[2][3]

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]

List of isotopes

Nuclide[5]
[n 1]		 Z N Isotopic mass (Da)[6]
[n 2][n 3]		 Half-life
[n 4]		 Decay
mode
[n 5]		 Daughter
isotope
[n 6][n 7]		 Spin and
parity
[n 8][n 4]		 Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion Range of variation
164Ir[7] 77 87 163.99220(44)# <0.5 µs p? 163Os 2−#
164mIr 270(110)# keV 70(10) µs p (96%) 163Os 9+#
α (4%) 160mRe
165Ir 77 88 164.98752(23)# 1.20+0.82
−0.74 μs[8]		 p 164Os (1/2+)
165mIr[9] ~255 keV 340(40) µs p (88%) 164Os (11/2−)
α (12%) 161mRe
166Ir 77 89 165.98582(22)# 10.5(22) ms α (93%) 162Re (2−)
p (7%) 165Os
166mIr 172(6) keV 15.1(9) ms α (98.2%) 162Re (9+)
p (1.8%) 165Os
167Ir 77 90 166.981665(20) 35.2(20) ms α (48%) 163Re 1/2+
p (32%) 166Os
β+ (20%) 167Os
167mIr 175.3(22) keV 30.0(6) ms α (80%) 163Re 11/2−
β+ (20%) 167Os
p (.4%) 166Os
168Ir 77 91 167.97988(16)# 161(21) ms α 164Re (2-)
β+ (rare) 168Os
168mIr 50(100)# keV 125(40) ms α 164Re (9+)
169Ir 77 92 168.976295(28) 780(360) ms
[0.64(+46−24) s]		 α 165Re (1/2+)
β+ (rare) 169Os
169mIr 154(24) keV 308(22) ms α (72%) 165Re (11/2−)
β+ (28%) 169Os
170Ir 77 93 169.97497(11)# 910(150) ms
[0.87(+18−12) s]		 β+ (64%) 170Os low#
α (36%) 166Re
170mIr 160(50)# keV 440(60) ms α (36%) 166Re (8+)
β+ 170Os
IT 170Ir
171Ir 77 94 170.97163(4) 3.6(10) s
[3.2(+13−7) s]		 α (58%) 167Re 1/2+
β+ (42%) 171Os
171mIr 180(30)# keV 1.40(10) s (11/2−)
172Ir 77 95 171.970610(30) 4.4(3) s β+ (98%) 172Os (3+)
α (2%) 168Re
172mIr 280(100)# keV 2.0(1) s β+ (77%) 172Os (7+)
α (23%) 168Re
173Ir 77 96 172.967502(15) 9.0(8) s β+ (93%) 173Os (3/2+,5/2+)
α (7%) 169Re
173mIr 253(27) keV 2.20(5) s β+ (88%) 173Os (11/2−)
α (12%) 169Re
174Ir 77 97 173.966861(30) 7.9(6) s β+ (99.5%) 174Os (3+)
α (.5%) 170Re
174mIr 193(11) keV 4.9(3) s β+ (99.53%) 174Os (7+)
α (.47%) 170Re
175Ir 77 98 174.964113(21) 9(2) s β+ (99.15%) 175Os (5/2−)
α (.85%) 171Re
176Ir 77 99 175.963649(22) 8.3(6) s β+ (97.9%) 176Os
α (2.1%) 172Re
177Ir 77 100 176.961302(21) 30(2) s β+ (99.94%) 177Os 5/2−
α (.06%) 173Re
178Ir 77 101 177.961082(21) 12(2) s β+ 178Os
179Ir 77 102 178.959122(12) 79(1) s β+ 179Os (5/2)−
180Ir 77 103 179.959229(23) 1.5(1) min β+ 180Os (4,5)(+#)
181Ir 77 104 180.957625(28) 4.90(15) min β+ 181Os (5/2)−
182Ir 77 105 181.958076(23) 15(1) min β+ 182Os (3+)
183Ir 77 106 182.956846(27) 57(4) min β+ ( 99.95%) 183Os 5/2−
α (.05%) 179Re
184Ir 77 107 183.95748(3) 3.09(3) h β+ 184Os 5−
184m1Ir 225.65(11) keV 470(30) µs 3+
184m2Ir 328.40(24) keV 350(90) ns (7)+
185Ir 77 108 184.95670(3) 14.4(1) h β+ 185Os 5/2−
186Ir 77 109 185.957946(18) 16.64(3) h β+ 186Os 5+
186mIr 0.8(4) keV 1.92(5) h β+ 186Os 2−
IT (rare) 186Ir
187Ir 77 110 186.957363(7) 10.5(3) h β+ 187Os 3/2+
187m1Ir 186.15(4) keV 30.3(6) ms IT 187Ir 9/2−
187m2Ir 433.81(9) keV 152(12) ns 11/2−
188Ir 77 111 187.958853(8) 41.5(5) h β+ 188Os 1−
188mIr 970(30) keV 4.2(2) ms IT 188Ir 7+#
β+ (rare) 188Os
189Ir 77 112 188.958719(14) 13.2(1) d EC 189Os 3/2+
189m1Ir 372.18(4) keV 13.3(3) ms IT 189Ir 11/2−
189m2Ir 2333.3(4) keV 3.7(2) ms (25/2)+
190Ir 77 113 189.9605460(18) 11.78(10) d β+ 190Os 4−
190m1Ir 26.1(1) keV 1.120(3) h IT 190Ir (1−)
190m2Ir 36.154(25) keV >2 µs (4)+
190m3Ir 376.4(1) keV 3.087(12) h (11)−
191Ir 77 114 190.9605940(18) Observationally Stable[n 9] 3/2+ 0.373(2)
191m1Ir 171.24(5) keV 4.94(3) s IT 191Ir 11/2−
191m2Ir 2120(40) keV 5.5(7) s
192Ir 77 115 191.9626050(18) 73.827(13) d β− (95.24%) 192Pt 4+
EC (4.76%) 192Os
192m1Ir 56.720(5) keV 1.45(5) min 1−
192m2Ir 168.14(12) keV 241(9) y (11−)
193Ir 77 116 192.9629264(18) Observationally Stable[n 10] 3/2+ 0.627(2)
193mIr 80.240(6) keV 10.53(4) d IT 193Ir 11/2−
194Ir 77 117 193.9650784(18) 19.28(13) h β− 194Pt 1−
194m1Ir 147.078(5) keV 31.85(24) ms IT 194Ir (4+)
194m2Ir 370(70) keV 171(11) d (10,11)(−#)
195Ir 77 118 194.9659796(18) 2.5(2) h β− 195Pt 3/2+
195mIr 100(5) keV 3.8(2) h β− (95%) 195Pt 11/2−
IT (5%) 195Ir
196Ir 77 119 195.96840(4) 52(1) s β− 196Pt (0−)
196mIr 210(40) keV 1.40(2) h β− (99.7%) 196Pt (10,11−)
IT 196Ir
197Ir 77 120 196.969653(22) 5.8(5) min β− 197Pt 3/2+
197mIr 115(5) keV 8.9(3) min β− (99.75%) 197Pt 11/2−
IT (.25%) 197Ir
198Ir 77 121 197.97228(21)# 8(1) s β− 198Pt
199Ir 77 122 198.97380(4) 7(5) s β− 199Pt 3/2+#
199mIr 130(40)# keV 235(90) ns IT 199Ir 11/2−#
200Ir 77 123 199.976800(210)# 43(6) s β− 200Pt (2-, 3-)
201Ir 77 124 200.978640(210)# 21(5) s β− 201Pt (3/2+)
202Ir 77 125 201.981990(320)# 11(3) s β− 202Pt (2-)
202mIr 2000(1000)# keV 3.4(0.6) µs IT 202Ir
This table header & footer:
  1. ↑ mIr – Excited nuclear isomer.
  2. ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. 1 2 3 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. ↑ Modes of decay:
    EC:Electron capture
    IT:Isomeric transition
    p:Proton emission
  6. ↑ Bold italics symbol as daughter – Daughter product is nearly stable.
  7. ↑ Bold symbol as daughter – Daughter product is stable.
  8. ↑ ( ) spin value – Indicates spin with weak assignment arguments.
  9. ↑ Believed to undergo α decay to 187Re
  10. ↑ Believed to undergo α decay to 189Re

Iridium-192

Iridium-192 (symbol 192Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.[10] 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.[11] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal.[12]

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).[13][14] 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.

References

  1. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ↑ "Standard Atomic Weights: Iridium". CIAAW. 2017.
  3. ↑ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; et al. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ↑ Belli, P.; Bernabei, R.; Danevich, F. A.; et al. (2019). "Experimental searches for rare alpha and beta decays". European Physical Journal A. 55 (8): 140–1–140–7. arXiv:1908.11458. Bibcode:2019EPJA...55..140B. doi:10.1140/epja/i2019-12823-2. ISSN 1434-601X. S2CID 201664098.
  5. ↑ Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
    Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
  6. ↑ Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
  7. ↑ 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. ISSN 0556-2813. Retrieved 21 June 2023.
  8. ↑ Hilton, Joshua Ben. "Decays of new nuclides 169Au, 170Hg, 165Pt and the ground state of 165Ir discovered using MARA". University of Liverpool. ProQuest 2448649087. Retrieved 21 June 2023.
  9. ↑ 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. ISSN 0556-2813. Retrieved 21 June 2023.
  10. ↑ "Radioisotope Brief: Iridium-192 (Ir-192)". Retrieved 20 March 2012.
  11. ↑ Baggerly, Leo L. (1956). The radioactive decay of Iridium-192 (PDF) (Ph.D. thesis). Pasadena, Calif.: California Institute of Technology. pp. 1, 2, 7. doi:10.7907/26VA-RB25.
  12. ↑ "Isotope Supplier: Stable Isotopes and Radioisotopes from ISOFLEX - Iridium-192". www.isoflex.com. Retrieved 2017-10-11.
  13. ↑ Delacroix, D; Guerre, J P; Leblanc, P; Hickman, C (2002). Radionuclide and Radiation Protection Data Handbook (PDF). Radiation Protection Dosimetry. Vol. 98, no. 1 (2nd ed.). Ashford, Kent: Nuclear Technology Publishing. pp. 9–168. doi:10.1093/OXFORDJOURNALS.RPD.A006705. ISBN 1870965876. PMID 11916063. S2CID 123447679. Archived from the original (PDF) on 2019-08-22.
  14. ↑ Unger, L M; Trubey, D K (May 1982). Specific Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological Assessment (PDF) (Report). Oak Ridge National Laboratory. Archived from the original (PDF) on 22 March 2018.
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