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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