Isotopes of iridium

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

Standard atomic mass: 192.217(3) u

Iridium-192

Iridium-192 (symbol 192Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days.[1] 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.[2]

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.[3] 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 US Nuclear Regulatory Commission in which radioactive materials have gone missing in quantities large enough to make a dirty bomb.[4]

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[5][n 1]
daughter
isotope(s)[n 2]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
164Ir 77 87 163.99220(44)# 1# ms 2-#
164mIr 270(110)# keV 94(27) µs 9+#
165Ir 77 88 164.98752(23)# <1# µs p 164Os 1/2+#
α (rare) 161Re
165mIr 180(50)# keV 300(60) µs p (87%) 164Os 11/2-
α (13%) 161Re
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 high
β+ (rare) 168Os
168mIr 50(100)# keV 125(40) ms α 164Re low
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 270(70)# keV 440(60) ms high#
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 95 171.97046(11)# 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 3] 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) a (11-)
193Ir 77 116 192.9629264(18) Observationally Stable[n 4] 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) 20# s β 199Pt 3/2+#
  1. Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  2. Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
  3. Believed to undergo α decay to 187Re
  4. Believed to undergo α decay to 189Re

Notes

References

  1. "Radioisotope Brief: Iridium-192 (Ir-192)". Retrieved 20 March 2012.
  2. Braggerly, L.L. (1956). The radioactive decay of Iridium-192 (Pd.D. Thesis). Pasadena, CA: California Institute of Technology. pp. 1, 2, 7.
  3. Charles Hellier (2003). Handbook of Nondestructive Evaluation. McGraw-Hill. p. 6.20. ISBN 0-07-028121-1.
  4. Steve Coll (March 12, 2007). "The Unthinkable". The New Yorker. Retrieved 2007-03-09.
  5. Added info from http://www.nucleonica.net/unc.aspx

External links

Isotopes of osmium Isotopes of iridium Isotopes of platinum
Table of nuclides