Isotopes of iridium

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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[edit]

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[edit]

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[edit]

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References[edit]

  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[edit]


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