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Isotopes of iridium

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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]

Quick Facts Main isotopes, Decay ...
Isotopes of iridium (77Ir)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
191Ir 37.3% stable
192Ir synth 73.827 d β− 192Pt
ε 192Os
192m2Ir synth 241 y IT 192Ir
193Ir 62.7% stable
Standard atomic weight Ar°(Ir)
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More information Nuclide, Z ...
Nuclide
[n 1]		 Z N Isotopic mass (Da)[5]
[n 2][n 3]		 Half-life[1]
[n 4]		 Decay
mode[1]
[n 5]		 Daughter
isotope
[n 6][n 7]		 Spin and
parity[1]
[n 8][n 4]		 Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion[1] Range of variation
164Ir[n 9][6] 77 87 163.99197(34)# <0.5 μs p? 163Os 2−#
164mIr 260(100)# keV 70(10) μs p (96%) 163Os (9+)
α (4%) 160mRe
165Ir 77 88 165.98572(22)# 1.20+0.82
−0.74 μs[7]		 p 164Os (1/2+)
165mIr[6] ~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 171(6) keV 15.1(9) ms α (98.2%) 162Re (9)+
p (1.8%) 165Os
167Ir 77 90 166.981672(20) 29.3(6) ms α (43.5%) 163Re 1/2+
p (38.6%) 166Os
β+ (17.9%) 167Os
167mIr 175.5(21) keV 28.5(5) ms α (89%) 163Re 11/2−
β+ (11%) 167Os
p (0.41%) 166Os
168Ir 77 91 167.979961(59) 230(50) ms α 164Re (2)-
168mIr[n 10] 40(250) keV 163(16) ms α (77%) 164Re (9,10)+
β+? 168Os
β+, p? 167Re
169Ir 77 92 168.976282(25) 353(4) ms α (53%) 165Re (1/2+)
β+ (47%) 169Os
169mIr 153(22) keV 280(1) ms α (79%) 165Re (11/2−)
β+? 169Os
p? 168Os
170Ir 77 93 169.97511(11)# 910(150) ms β+ (94.8%) 170Os (3−)
α (5.2%) 166Re
170mIr[n 10] 40(50)# keV 811(18) ms α (38%) 166Re (8+)
β+? 170Os
IT? 170Ir
171Ir 77 94 170.971646(41) 3.1(3) s β+ (85%) 171Os 1/2+
α (15%) 167Re
171mIr 164(11)# keV 1.47(6) s α (54%) 167Re (11/2−)
β+? 171Os
p? 170Os
172Ir 77 95 171.970607(35) 4.4(3) s β+ (~98%) 172Os (3−,4−)
α (~2%) 168Re
172mIr 139(10) keV 2.19(7) s β+ (90.5%) 172Os (7+)
α (9.5%) 168Re
173Ir 77 96 172.967505(11) 9.0(8) s β+ (96.5%) 173Os (1/2+,3/2+)
α (3.5%) 169Re
173mIr 226(9) keV 2.20(5) s β+ (88%) 173Os 11/2−
α (12%) 169Re
174Ir 77 97 173.966950(12) 7.9(6) s β+ (99.5%) 174Os (2+,3−)
α (0.5%) 170Re
174mIr 124(16) keV 4.9(3) s β+ (97.5%) 174Os (6,7,8,9)
α (2.5%) 170Re
175Ir 77 98 174.964150(13) 9(2) s β+ (99.15%) 175Os (1/2+)
α (0.85%) 171Re
175m1Ir 50(40)# keV 33(4) s β+ 175Os 9/2−#
175m2Ir 97.4(7) keV 6.58(15) μs IT 175Ir (5/2−)
176Ir 77 99 175.9636263(87) 8.7(5) s β+ (96.9%) 176Os (3+)
α (3.1%) 172Re
177Ir 77 100 176.961302(21) 29.8(17) s β+ (99.94%) 177Os 5/2−
α (0.06%) 173Re
177mIr 180.9(4) keV >100 ns IT 177Ir (5/2+)
178Ir 77 101 177.961079(20) 12(2) s β+ 178Os 3+#
179Ir 77 102 178.959118(10) 79(1) s β+ 179Os (5/2)−
180Ir 77 103 179.959229(23) 1.5(1) min β+ 180Os (5+)
181Ir 77 104 180.9576347(56) 4.90(15) min β+ 181Os 5/2−
181m1Ir 289.33(13) keV 298 ns IT 181Ir 5/2+
181m2Ir 366.30(22) keV 126(6) ns IT 181Ir 9/2−
182Ir 77 105 181.958076(23) 15.0(10) min β+ 182Os 3+
182m1Ir 71.02(17) keV 170(40) ns IT 182Ir (5)+
182m2Ir 176.4(3) keV 130(50) ns IT 182Ir (6−)
183Ir 77 106 182.956841(26) 58(5) min β+ 183Os 5/2−
184Ir 77 107 183.957476(30) 3.09(3) h β+ 184Os 5−
184m1Ir 225.65(11) keV 470(30) μs IT 184Ir 3+
184m2Ir 328.40(24) keV 350(90) ns IT 184Ir 7+
185Ir 77 108 184 956698(30) 14.4(1) h β+ 185Os 5/2−
185mIr 2197(23) keV 120(20) ns IT 185Ir (23/2,25/2)#
186Ir 77 109 185.957947(18) 16.64(3) h β+ 186Os 5+
186mIr 0.8(4) keV 1.92(5) h β+ (~75%) 186Os 2−
IT (~25%) 186Ir
187Ir 77 110 186.957542(30) 10.5(3) h β+ 187Os 3/2+
187m1Ir 186.16(4) keV 30.3(6) ms IT 187Ir 9/2−
187m2Ir 433.75(6) keV 152(12) ns IT 187Ir 11/2−
187m3Ir 2487.7(4) keV 1.8(5) μs IT 187Ir 29/2−
188Ir 77 111 187.958835(10) 41.5(5) h β+ 188Os 1−
188mIr 964(23) keV 4.15(15) ms IT 188Ir 11−#
189Ir 77 112 188.958723(14) 13.2(1) d EC 189Os 3/2+
189m1Ir 372.17(4) keV 13.3(3) ms IT 189Ir 11/2−
189m2Ir 2332.8(3) keV 3.7(2) ms IT 189Ir 25/2+
190Ir 77 113 189.9605434(15) 11.7511(20) d[8] EC 190Os 4−
β+ (<0.002%)[8]
190m1Ir 26.1(1) keV 1.120(3) h IT 190Ir 1−
190m2Ir 36.154(25) keV >2 μs IT 190Ir 4+
190m3Ir 376.4(1) keV 3.087(12) h EC (91.4%) 190Os 11−
IT (8.6%) 190Ir
191Ir 77 114 190.9605915(14) Observationally Stable[n 11] 3/2+ 0.373(2)
191m1Ir 171.29(4) keV 4.899(23) s IT 191Ir 11/2−
191m2Ir 2101.0(9) keV 5.7(4) s IT 191Ir 31/2(+)
192Ir 77 115 191.9626024(14) 73.820(14) d β− (95.24%) 192Pt 4+
EC (4.76%) 192Os
192m1Ir 56.720(5) keV 1.45(5) min IT (99.98%) 192Ir 1−
β− (0.0175%) 192Pt
192m2Ir 168.14(12) keV 241(9) y IT 192Ir (11−)
193Ir 77 116 192.9629238(14) Observationally Stable[n 12] 3/2+ 0.627(2)
193m1Ir 80.238(6) keV 10.53(4) d IT 193Ir 11/2−
193m2Ir 2278.9(5) keV 124.8(21) μs IT 193Ir 31/2+
194Ir 77 117 193.9650757(14) 19.35(7) h β− 194Pt 1−
194m1Ir 147.072(2) keV 31.85(24) ms IT 194Ir 4+
194m2Ir 370(70) keV 171(11) d β− 194Pt (11−)
195Ir 77 118 194.9659769(14) 2.29(17) h β− 195Pt 3/2+
195m1Ir 100(5) keV 3.74(7) h β− 195Pt 11/2−
195m2Ir 2354(6) keV 4.4(6) μs IT 195Ir (27/2+)
196Ir 77 119 195.968400(41) 52.0(11) s β− 196Pt (1,2−)
196mIr 210(40) keV 1.40(2) h β− 196Pt 11−#
197Ir 77 120 196.969657(22) 5.8(5) min β− 197Pt 3/2+
197m1Ir 115(5) keV 8.9(3) min β− 197Pt 11/2−
197m2Ir 1700(500)# keV 30(8) μs IT 197Ir
197m3Ir 2800(500)# keV 15(9) μs IT 197Ir
198Ir 77 121 197.97240(22)# 8.7(4) s β− 198Pt 1−
199Ir 77 122 198.973807(44) 7(5) s β− 199Pt 3/2+#
200Ir 77 123 199.97684(21)# 43(6) s β− 200Pt (2-, 3-)
201Ir 77 124 200.97870(22)# 21(5) s β− 201Pt (3/2+)
202Ir 77 125 201.98214(32)# 11(3) s β− 202Pt (2-)
202mIr 2600(300)# keV 3.4(6) μs IT 202Ir
203Ir 77 126 202.98457(43)# 7# s
[>300 ns]		 3/2+#
203mIr 2140(50)# keV 798(350) ns IT 203Ir
204Ir 77 127 203.98973(43)# 2# s
[>300 ns]		 3/2+#
205Ir 77 125 204.99399(54)# 1# s
[>300 ns]		 3/2+#
This table header & footer:
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  1. [n 1]
    mIr – Excited nuclear isomer.
  2. [n 2]
    ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. [n 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. [n 4]
    # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. [n 5]
    Modes of decay:
    α:Alpha decay
    β+:Positron emission
    EC:Electron capture
    β−:Beta decay
    IT:Isomeric transition
    p:Proton emission
  6. [n 6]
    Bold italics symbol as daughter – Daughter product is nearly stable.
  7. [n 7]
    Bold symbol as daughter – Daughter product is stable.
  8. [n 8]
    ( ) spin value – Indicates spin with weak assignment arguments.
  9. [n 9]
    Discovery of this isotope is unconfirmed
  10. [N 10]
    Order of ground state and isomer is uncertain.
  11. [N 11]
    Believed to undergo α decay to 187Re[9][10]
  12. [N 12]
    Believed to undergo α decay to 189Re[9]

Iridium-192

Main article: Iridium-192

Iridium-192 (symbol 192Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.[11] 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.[12] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal.[13]

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).[14][15] 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

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