Isotopes of iridium

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Isotopes of iridium  (77Ir)
Main isotopes [1] Decay
abun­dance half-life (t1/2) mode pro­duct
191Ir37.3% stable
192Ir synth73.827 d β 192Pt
ε 192Os
192m2Irsynth241 y IT 192Ir
193Ir62.7%stable
Standard atomic weight Ar°(Ir)

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]

Contents

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 proportionRange of variation
164Ir [7] 7787163.99220(44)#<0.5 μs p?163Os2−#
164mIr270(110)# keV70(10) μsp (96%)163Os9+#
α (4%)160mRe
165Ir7788164.98752(23)#1.20+0.82
−0.74
 μs
[8]
p164Os(1/2+)
165mIr [9] ~255 keV340(40) μsp (88%)164Os(11/2−)
α (12%)161mRe
166Ir7789165.98582(22)#10.5(22) msα (93%)162Re(2−)
p (7%)165Os
166mIr172(6) keV15.1(9) msα (98.2%)162Re(9+)
p (1.8%)165Os
167Ir7790166.981665(20)35.2(20) msα (48%)163Re1/2+
p (32%)166Os
β+ (20%)167Os
167mIr175.3(22) keV30.0(6) msα (80%)163Re11/2−
β+ (20%)167Os
p (.4%)166Os
168Ir7791167.97988(16)#161(21) msα164Re(2-)
β+ (rare)168Os
168mIr50(100)# keV125(40) msα164Re(9+)
169Ir7792168.976295(28)780(360) ms
[640+460
−240
 ms
]
α165Re(1/2+)
β+ (rare)169Os
169mIr154(24) keV308(22) msα (72%)165Re(11/2−)
β+ (28%)169Os
170Ir7793169.97497(11)#910(150) ms
[870+180
−120
 ms
]
β+ (64%)170Oslow#
α (36%)166Re
170mIr160(50)# keV440(60) msα (36%)166Re(8+)
β+170Os
IT170Ir
171Ir7794170.97163(4)3.6(10) s
[3.2+13
−7
 s
]
α (58%)167Re1/2+
β+ (42%)171Os
171mIr180(30)# keV1.40(10) s(11/2−)
172Ir7795171.970610(30)4.4(3) sβ+ (98%)172Os(3+)
α (2%)168Re
172mIr280(100)# keV2.0(1) sβ+ (77%)172Os(7+)
α (23%)168Re
173Ir7796172.967502(15)9.0(8) sβ+ (93%)173Os(3/2+,5/2+)
α (7%)169Re
173mIr253(27) keV2.20(5) sβ+ (88%)173Os(11/2−)
α (12%)169Re
174Ir7797173.966861(30)7.9(6) sβ+ (99.5%)174Os(3+)
α (.5%)170Re
174mIr193(11) keV4.9(3) sβ+ (99.53%)174Os(7+)
α (.47%)170Re
175Ir7798174.964113(21)9(2) sβ+ (99.15%)175Os(5/2−)
α (.85%)171Re
176Ir7799175.963649(22)8.3(6) sβ+ (97.9%)176Os
α (2.1%)172Re
177Ir77100176.961302(21)30(2) sβ+ (99.94%)177Os5/2−
α (.06%)173Re
178Ir77101177.961082(21)12(2) sβ+178Os
179Ir77102178.959122(12)79(1) sβ+179Os(5/2)−
180Ir77103179.959229(23)1.5(1) minβ+180Os(4,5)(+#)
181Ir77104180.957625(28)4.90(15) minβ+181Os(5/2)−
182Ir77105181.958076(23)15(1) minβ+182Os(3+)
183Ir77106182.956846(27)57(4) minβ+ ( 99.95%)183Os5/2−
α (.05%)179Re
184Ir77107183.95748(3)3.09(3) hβ+184Os5−
184m1Ir225.65(11) keV470(30) μs3+
184m2Ir328.40(24) keV350(90) ns(7)+
185Ir77108184.95670(3)14.4(1) hβ+185Os5/2−
186Ir77109185.957946(18)16.64(3) hβ+186Os5+
186mIr0.8(4) keV1.92(5) hβ+186Os2−
IT (rare)186Ir
187Ir77110186.957363(7)10.5(3) hβ+187Os3/2+
187m1Ir186.15(4) keV30.3(6) msIT187Ir9/2−
187m2Ir433.81(9) keV152(12) ns11/2−
188Ir77111187.958853(8)41.5(5) hβ+188Os1−
188mIr970(30) keV4.2(2) msIT188Ir7+#
β+ (rare)188Os
189Ir77112188.958719(14)13.2(1) d EC 189Os3/2+
189m1Ir372.18(4) keV13.3(3) msIT189Ir11/2−
189m2Ir2333.3(4) keV3.7(2) ms(25/2)+
190Ir77113189.9605460(18)11.7511(20) d [10] EC190Os4−
β+ (<0.002%) [10]
190m1Ir26.1(1) keV1.120(3) hIT190Ir(1)−
190m2Ir36.154(25) keV>2 μs(4)+
190m3Ir376.4(1) keV3.087(12) hEC (91.4%) [10] 190Os(11)−
IT (8.6%) [10] 190Ir
191Ir77114190.9605940(18) Observationally Stable [n 9] 3/2+0.373(2)
191m1Ir171.24(5) keV4.94(3) sIT191Ir11/2−
191m2Ir2120(40) keV5.5(7) s
192Ir 77115191.9626050(18)73.827(13) dβ (95.24%)192Pt4+
EC (4.76%)192Os
192m1Ir56.720(5) keV1.45(5) minIT (98.25%)192Ir1−
β (1.75%)192Pt
192m2Ir168.14(12) keV241(9) yIT192Ir(11−)
193Ir77116192.9629264(18)Observationally Stable [n 10] 3/2+0.627(2)
193mIr80.240(6) keV10.53(4) dIT193Ir11/2−
194Ir77117193.9650784(18)19.28(13) hβ194Pt1−
194m1Ir147.078(5) keV31.85(24) msIT194Ir(4+)
194m2Ir370(70) keV171(11) d(10,11)(−#)
195Ir77118194.9659796(18)2.5(2) hβ195Pt3/2+
195mIr100(5) keV3.8(2) hβ (95%)195Pt11/2−
IT (5%)195Ir
196Ir77119195.96840(4)52(1) sβ196Pt(0−)
196mIr210(40) keV1.40(2) hβ (99.7%)196Pt(10,11−)
IT196Ir
197Ir77120196.969653(22)5.8(5) minβ197Pt3/2+
197mIr115(5) keV8.9(3) minβ (99.75%)197Pt11/2−
IT (.25%)197Ir
198Ir77121197.97228(21)#8(1) sβ198Pt
199Ir77122198.97380(4)7(5) sβ199Pt3/2+#
199mIr130(40)# keV235(90) nsIT199Ir11/2−#
200Ir77123199.976800(210)#43(6) sβ200Pt(2-, 3-)
201Ir77124200.978640(210)#21(5) sβ201Pt(3/2+)
202Ir77125201.981990(320)#11(3) sβ202Pt(2-)
202mIr2000(1000)# keV3.4(0.6) μsIT202Ir
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. [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.

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